From c0be6aac0b20f1e656ee05e97bcdf2af98de36c4 Mon Sep 17 00:00:00 2001
From: Etienne Bacher <52219252+etiennebacher@users.noreply.github.com>
Date: Fri, 6 Oct 2023 13:21:43 +0200
Subject: [PATCH 01/25] start work on write_csv()

---
 R/dataframe__frame.R           | 75 ++++++++++++++++++++++++++++++++++
 R/extendr-wrappers.R           | 10 +++++
 R/utils.R                      |  6 +++
 src/rust/src/rdataframe/mod.rs | 56 +++++++++++++++++++++++++
 4 files changed, 147 insertions(+)

diff --git a/R/dataframe__frame.R b/R/dataframe__frame.R
index 2fb60866e..23c3f7374 100644
--- a/R/dataframe__frame.R
+++ b/R/dataframe__frame.R
@@ -1599,3 +1599,78 @@ DataFrame_sample = function(
   ) |>
     unwrap("in $sample():")
 }
+
+
+
+#' Write to comma-separated values (CSV) file
+#'
+#' @param path File path to which the result should be written.
+#' @param has_header Whether to include header in the CSV output.
+#' @param separator Separate CSV fields with this symbol.
+#' @param line_terminator String used to end each row.
+#' @param quote Byte to use as quoting character.
+#' @param batch_size Number of rows that will be processed per thread.
+#' @param datetime_format A format string, with the specifiers defined by the
+#' chrono Rust crate. If no format specified, the default fractional-second
+#' precision is inferred from the maximum timeunit found in the frame’s Datetime
+#'  cols (if any).
+#' @param date_format A format string, with the specifiers defined by the chrono
+#' Rust crate.
+#' @param time_format A format string, with the specifiers defined by the chrono
+#' Rust crate.
+#' @param float_precision Number of decimal places to write, applied to both
+#' Float32 and Float64 datatypes.
+#' @param null_values A string representing null values (defaulting to the empty
+#' string).
+#' @param quote_style Determines the quoting strategy used.
+#' * "`necessary"` (default): This puts quotes around fields only when necessary.
+#'   They are necessary when fields contain a quote, delimiter or record
+#'   terminator. Quotes are also necessary when writing an empty record (which
+#'   is indistinguishable from a record with one empty field). This is the
+#'   default.
+#' * `"always"`: This puts quotes around every field.
+#' * `"non_numeric"`: This puts quotes around all fields that are non-numeric.
+#'   Namely, when writing a field that does not parse as a valid float or integer,
+#'   then quotes will be used even if they aren`t strictly necessary.
+
+# TODO: include "never" when bumping rust-polars to 0.34
+# * `"never"`: This never puts quotes around fields, even if that results in
+#   invalid CSV data (e.g.: by not quoting strings containing the separator).
+
+#' @return
+#' This doesn't return anything but creates a CSV file.
+#' @export
+#'
+#' @examples
+DataFrame_write_csv = function(
+    path,
+    has_header = TRUE,
+    separator = ",",
+    line_terminator = "\n",
+    quote = '"',
+    batch_size = 1024,
+    datetime_format = NULL,
+    date_format = NULL,
+    time_format = NULL,
+    float_precision = NULL,
+    null_values = "",
+    quote_style = "necessary"
+) {
+
+  if (file_ext(path) != "csv") {
+    stop("Argument `path` must the path to a CSV file.")
+  }
+
+  if (is.null(null_values)) {
+    stop("Argument `null_values` cannot be NULL.")
+  }
+
+  .pr$DataFrame$write_csv(
+    self,
+    path, has_header, utf8ToInt(separator), line_terminator, utf8ToInt(quote), batch_size,
+    datetime_format, date_format, time_format, float_precision,
+    null_values, quote_style
+  ) |>
+    unwrap("in $write_csv():") |>
+    invisible()
+}
diff --git a/R/extendr-wrappers.R b/R/extendr-wrappers.R
index 91338ef9a..89fcc6af6 100644
--- a/R/extendr-wrappers.R
+++ b/R/extendr-wrappers.R
@@ -179,6 +179,16 @@ DataFrame$sample_n <- function(n, with_replacement, shuffle, seed) .Call(wrap__D
 
 DataFrame$sample_frac <- function(frac, with_replacement, shuffle, seed) .Call(wrap__DataFrame__sample_frac, self, frac, with_replacement, shuffle, seed)
 
+DataFrame$write_csv <- function(path, has_header, separator, line_terminator, quote, batch_size,
+                                datetime_format, date_format, time_format, float_precision,
+                                null_values, quote_style) .Call(wrap__DataFrame__write_csv, self, path,
+                                                                has_header, separator,
+                                                                line_terminator, quote,
+                                                                batch_size,
+                                                                datetime_format, date_format,
+                                                                time_format, float_precision,
+                                                                null_values, quote_style)
+
 #' @export
 `$.DataFrame` <- function (self, name) { func <- DataFrame[[name]]; environment(func) <- environment(); func }
 
diff --git a/R/utils.R b/R/utils.R
index 5e7f071bd..93f9982a7 100644
--- a/R/utils.R
+++ b/R/utils.R
@@ -634,3 +634,9 @@ is_bool = function(x) {
 dtypes_are_struct = function(dtypes) {
   sapply(dtypes, \(dt) pl$same_outer_dt(dt, pl$Struct()))
 }
+
+# from tools::file_ext()
+file_ext <- function(x) {
+  pos <- regexpr("\\.([[:alnum:]]+)$", x)
+  ifelse(pos > -1L, substring(x, pos + 1L), "")
+}
diff --git a/src/rust/src/rdataframe/mod.rs b/src/rust/src/rdataframe/mod.rs
index 63f54048d..cbfba14aa 100644
--- a/src/rust/src/rdataframe/mod.rs
+++ b/src/rust/src/rdataframe/mod.rs
@@ -12,6 +12,8 @@ use crate::rlib;
 use crate::robj_to;
 use crate::rpolarserr::{polars_to_rpolars_err, RResult};
 
+use polars::prelude::{CsvWriter, QuoteStyle, SerWriter};
+
 pub use lazy::dataframe::*;
 
 use crate::conversion_s_to_r::pl_series_to_list;
@@ -420,7 +422,61 @@ impl DataFrame {
             .map_err(polars_to_rpolars_err)
             .map(DataFrame)
     }
+
+    pub fn write_csv(
+        &mut self,
+        path: Robj,
+        has_header: Robj,
+        separator: Robj,
+        line_terminator: Robj,
+        quote: Robj,
+        batch_size: Robj,
+        datetime_format: Robj,
+        date_format: Robj,
+        time_format: Robj,
+        float_precision: Robj,
+        null_value: Robj,
+        quote_style: Robj,        
+    ) -> List {
+
+        let null = robj_to!(Option, String, null_value).unwrap_or_default().unwrap();
+        let path = robj_to!(str, path).unwrap();
+        let f = std::fs::File::create(path).unwrap();
+        let qs = parse_quote_style(quote_style);    
+
+        let mut r = CsvWriter::new(f)
+            .has_header(robj_to!(bool, has_header).unwrap())
+            .with_delimiter(robj_to!(u8, separator).unwrap())
+            .with_line_terminator(robj_to!(String, line_terminator).unwrap())
+            .with_quoting_char(robj_to!(u8, quote).unwrap())
+            .with_batch_size(robj_to!(usize, batch_size).unwrap())
+            .with_datetime_format(robj_to!(Option, String, datetime_format).unwrap())
+            .with_date_format(robj_to!(Option, String, date_format).unwrap())
+            .with_time_format(robj_to!(Option, String, time_format).unwrap())
+            .with_float_precision(robj_to!(Option, usize, float_precision).unwrap())
+            .with_null_value(null)
+            .with_quote_style(qs);
+
+        let result = r
+            .finish(&mut self.0)
+            .map_err(polars_to_rpolars_err);
+
+        r_result_list(result)
+    }
 }
+
+pub fn parse_quote_style(x: Robj) -> QuoteStyle {
+    match robj_to!(Option, String, x).unwrap_or_default().unwrap().as_str() {
+        "always" => QuoteStyle::Always,
+        "necessary" => QuoteStyle::Necessary,
+        "non_numeric" => QuoteStyle::NonNumeric,
+        // "never" was added in 0.34
+        // "never" => QuoteStyle::Never,
+        _ => panic!("polars internal error: `quote_style` must be 'always', 'necessary' or 'non_numeric'.")
+    }
+}
+
+
 impl DataFrame {
     pub fn to_list_result(&self) -> Result<Robj, pl::PolarsError> {
         //convert DataFrame to Result of to R vectors, error if DataType is not supported

From 41397e4b135c4655a0cf18cdc3c6dd9de336b4d6 Mon Sep 17 00:00:00 2001
From: Etienne Bacher <52219252+etiennebacher@users.noreply.github.com>
Date: Fri, 6 Oct 2023 15:00:19 +0200
Subject: [PATCH 02/25] add some checks and tests

---
 R/dataframe__frame.R      |  9 ++++++
 tests/testthat/test-csv.R | 67 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 76 insertions(+)

diff --git a/R/dataframe__frame.R b/R/dataframe__frame.R
index 23c3f7374..7489aec32 100644
--- a/R/dataframe__frame.R
+++ b/R/dataframe__frame.R
@@ -1640,8 +1640,12 @@ DataFrame_sample = function(
 #' @return
 #' This doesn't return anything but creates a CSV file.
 #' @export
+#' @rdname IO_write_csv
 #'
 #' @examples
+#' dat = pl$DataFrame(mtcars)
+#'
+
 DataFrame_write_csv = function(
     path,
     has_header = TRUE,
@@ -1665,6 +1669,11 @@ DataFrame_write_csv = function(
     stop("Argument `null_values` cannot be NULL.")
   }
 
+  if (length(quote_style) == 0 ||
+      !quote_style %in% c("always", "necessary", "non_numeric")) {
+    stop("Argument `quote_style` must be one of 'always', 'necessary', or 'non_numeric'.")
+  }
+
   .pr$DataFrame$write_csv(
     self,
     path, has_header, utf8ToInt(separator), line_terminator, utf8ToInt(quote), batch_size,
diff --git a/tests/testthat/test-csv.R b/tests/testthat/test-csv.R
index 5fa7a0e76..87014ec1b 100644
--- a/tests/testthat/test-csv.R
+++ b/tests/testthat/test-csv.R
@@ -22,3 +22,70 @@ test_that("csv read iris", {
     iris
   )
 })
+
+
+dat = mtcars
+dat[c(1, 3, 9, 12), c(3, 4, 5)] = NA
+dat_pl = pl$DataFrame(dat)
+temp_noext = tempfile()
+temp_out = tempfile(fileext = ".csv")
+
+test_that("write_csv: path works", {
+  expect_error(
+    dat_pl$write_csv(temp_noext),
+    "must the path to a CSV file"
+  )
+
+  dat_pl$write_csv(temp_out)
+  expect_identical(
+    pl$read_csv(temp_out)$to_data_frame(),
+    dat,
+    ignore_attr = TRUE # rownames are lost when writing / reading from CSV
+  )
+})
+
+test_that("write_csv: null_values works", {
+  expect_error(
+    dat_pl$write_csv(temp_out, null_values = NULL),
+    "cannot be NULL"
+  )
+  dat_pl$write_csv(temp_out, null_values = "hello")
+  tmp = pl$read_csv(temp_out)$to_data_frame()
+  expect_true(is.character(tmp$disp) && is.character(tmp$hp) && is.character(tmp$drat))
+  expect_equal(tmp[1:2, "disp"], c("hello", "160.0"))
+})
+
+
+test_that("write_csv: null_values works", {
+  dat_pl$write_csv(temp_out, separator = "|")
+  expect_identical(
+    pl$read_csv(temp_out, sep = "|")$to_data_frame(),
+    dat,
+    ignore_attr = TRUE # rownames are lost when writing / reading from CSV
+  )
+})
+
+test_that("write_csv: quote_style and quote works", {
+  dat_pl2 = pl$DataFrame(iris)
+
+  expect_error(
+    dat_pl2$write_csv(temp_out, quote_style = "foo"),
+    "must be one of"
+  )
+
+  dat_pl2$write_csv(temp_out, quote_style = "always", quote = "+")
+  expect_identical(
+    head(pl$read_csv(temp_out)$to_data_frame()[["+Sepal.Length+"]], n = 2),
+    c("+5.1+", "+4.9+")
+  )
+
+  dat_pl2$write_csv(temp_out, quote_style = "non_numeric", quote = "+")
+  expect_identical(
+    head(pl$read_csv(temp_out)$to_data_frame()[["+Sepal.Length+"]], n = 2),
+    c(5.1, 4.9)
+  )
+  expect_identical(
+    head(pl$read_csv(temp_out)$to_data_frame()[["+Species+"]], n = 2),
+    c("+setosa+", "+setosa+")
+  )
+})

From fd27a9828b6f3c042d11858cf1a90ad421500573 Mon Sep 17 00:00:00 2001
From: Etienne Bacher <52219252+etiennebacher@users.noreply.github.com>
Date: Fri, 6 Oct 2023 15:00:26 +0200
Subject: [PATCH 03/25] add some docs

---
 man/IO_write_csv.Rd | 74 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 74 insertions(+)
 create mode 100644 man/IO_write_csv.Rd

diff --git a/man/IO_write_csv.Rd b/man/IO_write_csv.Rd
new file mode 100644
index 000000000..d20dee475
--- /dev/null
+++ b/man/IO_write_csv.Rd
@@ -0,0 +1,74 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/dataframe__frame.R
+\name{DataFrame_write_csv}
+\alias{DataFrame_write_csv}
+\title{Write to comma-separated values (CSV) file}
+\usage{
+DataFrame_write_csv(
+  path,
+  has_header = TRUE,
+  separator = ",",
+  line_terminator = "\\n",
+  quote = "\\"",
+  batch_size = 1024,
+  datetime_format = NULL,
+  date_format = NULL,
+  time_format = NULL,
+  float_precision = NULL,
+  null_values = "",
+  quote_style = "necessary"
+)
+}
+\arguments{
+\item{path}{File path to which the result should be written.}
+
+\item{has_header}{Whether to include header in the CSV output.}
+
+\item{separator}{Separate CSV fields with this symbol.}
+
+\item{line_terminator}{String used to end each row.}
+
+\item{quote}{Byte to use as quoting character.}
+
+\item{batch_size}{Number of rows that will be processed per thread.}
+
+\item{datetime_format}{A format string, with the specifiers defined by the
+chrono Rust crate. If no format specified, the default fractional-second
+precision is inferred from the maximum timeunit found in the frame’s Datetime
+cols (if any).}
+
+\item{date_format}{A format string, with the specifiers defined by the chrono
+Rust crate.}
+
+\item{time_format}{A format string, with the specifiers defined by the chrono
+Rust crate.}
+
+\item{float_precision}{Number of decimal places to write, applied to both
+Float32 and Float64 datatypes.}
+
+\item{null_values}{A string representing null values (defaulting to the empty
+string).}
+
+\item{quote_style}{Determines the quoting strategy used.
+\itemize{
+\item "\verb{necessary"} (default): This puts quotes around fields only when necessary.
+They are necessary when fields contain a quote, delimiter or record
+terminator. Quotes are also necessary when writing an empty record (which
+is indistinguishable from a record with one empty field). This is the
+default.
+\item \code{"always"}: This puts quotes around every field.
+\item \code{"non_numeric"}: This puts quotes around all fields that are non-numeric.
+Namely, when writing a field that does not parse as a valid float or integer,
+then quotes will be used even if they aren`t strictly necessary.
+}}
+}
+\value{
+This doesn't return anything but creates a CSV file.
+}
+\description{
+Write to comma-separated values (CSV) file
+}
+\examples{
+dat = pl$DataFrame(mtcars)
+
+}

From a05e98fedfe5d38131a330e4a1386b7c193be1bc Mon Sep 17 00:00:00 2001
From: Etienne Bacher <52219252+etiennebacher@users.noreply.github.com>
Date: Fri, 6 Oct 2023 15:10:28 +0200
Subject: [PATCH 04/25] simplify rust side

---
 NAMESPACE                      | 1 +
 src/rust/src/rdataframe/mod.rs | 8 +++-----
 2 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/NAMESPACE b/NAMESPACE
index e4235fb6f..8fe0a0b22 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -151,6 +151,7 @@ S3method(tail,LazyFrame)
 S3method(unique,DataFrame)
 S3method(unique,LazyFrame)
 export(.pr)
+export(DataFrame_write_csv)
 export(as_polars_series)
 export(knit_print.DataFrame)
 export(pl)
diff --git a/src/rust/src/rdataframe/mod.rs b/src/rust/src/rdataframe/mod.rs
index cbfba14aa..6c4a5c885 100644
--- a/src/rust/src/rdataframe/mod.rs
+++ b/src/rust/src/rdataframe/mod.rs
@@ -437,7 +437,7 @@ impl DataFrame {
         float_precision: Robj,
         null_value: Robj,
         quote_style: Robj,        
-    ) -> List {
+    ) -> RResult<()> {
 
         let null = robj_to!(Option, String, null_value).unwrap_or_default().unwrap();
         let path = robj_to!(str, path).unwrap();
@@ -457,11 +457,9 @@ impl DataFrame {
             .with_null_value(null)
             .with_quote_style(qs);
 
-        let result = r
+        r
             .finish(&mut self.0)
-            .map_err(polars_to_rpolars_err);
-
-        r_result_list(result)
+            .map_err(polars_to_rpolars_err)
     }
 }
 

From 769ee80d53f75ec5c4dd6ede61623aac68721e91 Mon Sep 17 00:00:00 2001
From: Etienne Bacher <52219252+etiennebacher@users.noreply.github.com>
Date: Fri, 6 Oct 2023 18:12:08 +0200
Subject: [PATCH 05/25] simplify rust side

---
 src/rust/src/rdataframe/mod.rs | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/src/rust/src/rdataframe/mod.rs b/src/rust/src/rdataframe/mod.rs
index 6c4a5c885..9eb65ecf9 100644
--- a/src/rust/src/rdataframe/mod.rs
+++ b/src/rust/src/rdataframe/mod.rs
@@ -444,7 +444,7 @@ impl DataFrame {
         let f = std::fs::File::create(path).unwrap();
         let qs = parse_quote_style(quote_style);    
 
-        let mut r = CsvWriter::new(f)
+        CsvWriter::new(f)
             .has_header(robj_to!(bool, has_header).unwrap())
             .with_delimiter(robj_to!(u8, separator).unwrap())
             .with_line_terminator(robj_to!(String, line_terminator).unwrap())
@@ -455,9 +455,7 @@ impl DataFrame {
             .with_time_format(robj_to!(Option, String, time_format).unwrap())
             .with_float_precision(robj_to!(Option, usize, float_precision).unwrap())
             .with_null_value(null)
-            .with_quote_style(qs);
-
-        r
+            .with_quote_style(qs)
             .finish(&mut self.0)
             .map_err(polars_to_rpolars_err)
     }
@@ -468,7 +466,7 @@ pub fn parse_quote_style(x: Robj) -> QuoteStyle {
         "always" => QuoteStyle::Always,
         "necessary" => QuoteStyle::Necessary,
         "non_numeric" => QuoteStyle::NonNumeric,
-        // "never" was added in 0.34
+        // "never" is available in rust-polars devel only for now (will be added in 0.34)
         // "never" => QuoteStyle::Never,
         _ => panic!("polars internal error: `quote_style` must be 'always', 'necessary' or 'non_numeric'.")
     }

From 296cec110d988a70fa7dd35da04cf934bfcbaa03 Mon Sep 17 00:00:00 2001
From: Etienne Bacher <52219252+etiennebacher@users.noreply.github.com>
Date: Mon, 9 Oct 2023 09:52:06 +0200
Subject: [PATCH 06/25] remove null_value check on R side

---
 R/dataframe__frame.R           | 4 ----
 src/rust/src/rdataframe/mod.rs | 6 +++---
 tests/testthat/test-csv.R      | 5 ++---
 3 files changed, 5 insertions(+), 10 deletions(-)

diff --git a/R/dataframe__frame.R b/R/dataframe__frame.R
index 7489aec32..d658ea8f4 100644
--- a/R/dataframe__frame.R
+++ b/R/dataframe__frame.R
@@ -1665,10 +1665,6 @@ DataFrame_write_csv = function(
     stop("Argument `path` must the path to a CSV file.")
   }
 
-  if (is.null(null_values)) {
-    stop("Argument `null_values` cannot be NULL.")
-  }
-
   if (length(quote_style) == 0 ||
       !quote_style %in% c("always", "necessary", "non_numeric")) {
     stop("Argument `quote_style` must be one of 'always', 'necessary', or 'non_numeric'.")
diff --git a/src/rust/src/rdataframe/mod.rs b/src/rust/src/rdataframe/mod.rs
index 9eb65ecf9..34c09ebac 100644
--- a/src/rust/src/rdataframe/mod.rs
+++ b/src/rust/src/rdataframe/mod.rs
@@ -436,13 +436,13 @@ impl DataFrame {
         time_format: Robj,
         float_precision: Robj,
         null_value: Robj,
-        quote_style: Robj,        
+        quote_style: Robj,
     ) -> RResult<()> {
 
-        let null = robj_to!(Option, String, null_value).unwrap_or_default().unwrap();
+        let null = robj_to!(String, null_value).unwrap();
         let path = robj_to!(str, path).unwrap();
         let f = std::fs::File::create(path).unwrap();
-        let qs = parse_quote_style(quote_style);    
+        let qs = parse_quote_style(quote_style);
 
         CsvWriter::new(f)
             .has_header(robj_to!(bool, has_header).unwrap())
diff --git a/tests/testthat/test-csv.R b/tests/testthat/test-csv.R
index 87014ec1b..6e2c69469 100644
--- a/tests/testthat/test-csv.R
+++ b/tests/testthat/test-csv.R
@@ -46,8 +46,7 @@ test_that("write_csv: path works", {
 
 test_that("write_csv: null_values works", {
   expect_error(
-    dat_pl$write_csv(temp_out, null_values = NULL),
-    "cannot be NULL"
+    dat_pl$write_csv(temp_out, null_values = NULL)
   )
   dat_pl$write_csv(temp_out, null_values = "hello")
   tmp = pl$read_csv(temp_out)$to_data_frame()
@@ -56,7 +55,7 @@ test_that("write_csv: null_values works", {
 })
 
 
-test_that("write_csv: null_values works", {
+test_that("write_csv: separator works", {
   dat_pl$write_csv(temp_out, separator = "|")
   expect_identical(
     pl$read_csv(temp_out, sep = "|")$to_data_frame(),

From 3861b30a5f583f4731bf79e4a01589d3801f1bcb Mon Sep 17 00:00:00 2001
From: eitsupi <ts1s1andn@gmail.com>
Date: Mon, 16 Oct 2023 14:26:01 +0000
Subject: [PATCH 07/25] auto formatting by `make all`

---
 R/extendr-wrappers.R           | 10 +---------
 src/rust/src/rdataframe/mod.rs | 12 ++++++++----
 2 files changed, 9 insertions(+), 13 deletions(-)

diff --git a/R/extendr-wrappers.R b/R/extendr-wrappers.R
index 1d12ef79a..17e1e7bef 100644
--- a/R/extendr-wrappers.R
+++ b/R/extendr-wrappers.R
@@ -189,15 +189,7 @@ DataFrame$sample_n <- function(n, with_replacement, shuffle, seed) .Call(wrap__D
 
 DataFrame$sample_frac <- function(frac, with_replacement, shuffle, seed) .Call(wrap__DataFrame__sample_frac, self, frac, with_replacement, shuffle, seed)
 
-DataFrame$write_csv <- function(path, has_header, separator, line_terminator, quote, batch_size,
-                                datetime_format, date_format, time_format, float_precision,
-                                null_values, quote_style) .Call(wrap__DataFrame__write_csv, self, path,
-                                                                has_header, separator,
-                                                                line_terminator, quote,
-                                                                batch_size,
-                                                                datetime_format, date_format,
-                                                                time_format, float_precision,
-                                                                null_values, quote_style)
+DataFrame$write_csv <- function(path, has_header, separator, line_terminator, quote, batch_size, datetime_format, date_format, time_format, float_precision, null_value, quote_style) .Call(wrap__DataFrame__write_csv, self, path, has_header, separator, line_terminator, quote, batch_size, datetime_format, date_format, time_format, float_precision, null_value, quote_style)
 
 #' @export
 `$.DataFrame` <- function (self, name) { func <- DataFrame[[name]]; environment(func) <- environment(); func }
diff --git a/src/rust/src/rdataframe/mod.rs b/src/rust/src/rdataframe/mod.rs
index b79a8e982..232af2078 100644
--- a/src/rust/src/rdataframe/mod.rs
+++ b/src/rust/src/rdataframe/mod.rs
@@ -460,7 +460,6 @@ impl DataFrame {
         null_value: Robj,
         quote_style: Robj,
     ) -> RResult<()> {
-
         let null = robj_to!(String, null_value).unwrap();
         let path = robj_to!(str, path).unwrap();
         let f = std::fs::File::create(path).unwrap();
@@ -484,17 +483,22 @@ impl DataFrame {
 }
 
 pub fn parse_quote_style(x: Robj) -> QuoteStyle {
-    match robj_to!(Option, String, x).unwrap_or_default().unwrap().as_str() {
+    match robj_to!(Option, String, x)
+        .unwrap_or_default()
+        .unwrap()
+        .as_str()
+    {
         "always" => QuoteStyle::Always,
         "necessary" => QuoteStyle::Necessary,
         "non_numeric" => QuoteStyle::NonNumeric,
         // "never" is available in rust-polars devel only for now (will be added in 0.34)
         // "never" => QuoteStyle::Never,
-        _ => panic!("polars internal error: `quote_style` must be 'always', 'necessary' or 'non_numeric'.")
+        _ => panic!(
+            "polars internal error: `quote_style` must be 'always', 'necessary' or 'non_numeric'."
+        ),
     }
 }
 
-
 impl DataFrame {
     pub fn to_list_result(&self) -> Result<Robj, pl::PolarsError> {
         //convert DataFrame to Result of to R vectors, error if DataType is not supported

From 6c221fe0611752e7a6b182727ef3b1fb0745f6d1 Mon Sep 17 00:00:00 2001
From: eitsupi <ts1s1andn@gmail.com>
Date: Mon, 16 Oct 2023 14:37:52 +0000
Subject: [PATCH 08/25] test: use snapshot tests

---
 tests/testthat/_snaps/csv.md | 392 +++++++++++++++++++++++++++++++++++
 tests/testthat/test-csv.R    |  24 +--
 2 files changed, 396 insertions(+), 20 deletions(-)
 create mode 100644 tests/testthat/_snaps/csv.md

diff --git a/tests/testthat/_snaps/csv.md b/tests/testthat/_snaps/csv.md
new file mode 100644
index 000000000..4cde591fe
--- /dev/null
+++ b/tests/testthat/_snaps/csv.md
@@ -0,0 +1,392 @@
+# write_csv: null_values works
+
+    Code
+      cat(readLines(temp_out), sep = "\n")
+    Output
+      mpg,cyl,disp,hp,drat,wt,qsec,vs,am,gear,carb
+      21.0,6.0,hello,hello,hello,2.62,16.46,0.0,1.0,4.0,4.0
+      21.0,6.0,160.0,110.0,3.9,2.875,17.02,0.0,1.0,4.0,4.0
+      22.8,4.0,hello,hello,hello,2.32,18.61,1.0,1.0,4.0,1.0
+      21.4,6.0,258.0,110.0,3.08,3.215,19.44,1.0,0.0,3.0,1.0
+      18.7,8.0,360.0,175.0,3.15,3.44,17.02,0.0,0.0,3.0,2.0
+      18.1,6.0,225.0,105.0,2.76,3.46,20.22,1.0,0.0,3.0,1.0
+      14.3,8.0,360.0,245.0,3.21,3.57,15.84,0.0,0.0,3.0,4.0
+      24.4,4.0,146.7,62.0,3.69,3.19,20.0,1.0,0.0,4.0,2.0
+      22.8,4.0,hello,hello,hello,3.15,22.9,1.0,0.0,4.0,2.0
+      19.2,6.0,167.6,123.0,3.92,3.44,18.3,1.0,0.0,4.0,4.0
+      17.8,6.0,167.6,123.0,3.92,3.44,18.9,1.0,0.0,4.0,4.0
+      16.4,8.0,hello,hello,hello,4.07,17.4,0.0,0.0,3.0,3.0
+      17.3,8.0,275.8,180.0,3.07,3.73,17.6,0.0,0.0,3.0,3.0
+      15.2,8.0,275.8,180.0,3.07,3.78,18.0,0.0,0.0,3.0,3.0
+      10.4,8.0,472.0,205.0,2.93,5.25,17.98,0.0,0.0,3.0,4.0
+      10.4,8.0,460.0,215.0,3.0,5.424,17.82,0.0,0.0,3.0,4.0
+      14.7,8.0,440.0,230.0,3.23,5.345,17.42,0.0,0.0,3.0,4.0
+      32.4,4.0,78.7,66.0,4.08,2.2,19.47,1.0,1.0,4.0,1.0
+      30.4,4.0,75.7,52.0,4.93,1.615,18.52,1.0,1.0,4.0,2.0
+      33.9,4.0,71.1,65.0,4.22,1.835,19.9,1.0,1.0,4.0,1.0
+      21.5,4.0,120.1,97.0,3.7,2.465,20.01,1.0,0.0,3.0,1.0
+      15.5,8.0,318.0,150.0,2.76,3.52,16.87,0.0,0.0,3.0,2.0
+      15.2,8.0,304.0,150.0,3.15,3.435,17.3,0.0,0.0,3.0,2.0
+      13.3,8.0,350.0,245.0,3.73,3.84,15.41,0.0,0.0,3.0,4.0
+      19.2,8.0,400.0,175.0,3.08,3.845,17.05,0.0,0.0,3.0,2.0
+      27.3,4.0,79.0,66.0,4.08,1.935,18.9,1.0,1.0,4.0,1.0
+      26.0,4.0,120.3,91.0,4.43,2.14,16.7,0.0,1.0,5.0,2.0
+      30.4,4.0,95.1,113.0,3.77,1.513,16.9,1.0,1.0,5.0,2.0
+      15.8,8.0,351.0,264.0,4.22,3.17,14.5,0.0,1.0,5.0,4.0
+      19.7,6.0,145.0,175.0,3.62,2.77,15.5,0.0,1.0,5.0,6.0
+      15.0,8.0,301.0,335.0,3.54,3.57,14.6,0.0,1.0,5.0,8.0
+      21.4,4.0,121.0,109.0,4.11,2.78,18.6,1.0,1.0,4.0,2.0
+
+# write_csv: separator works
+
+    Code
+      cat(readLines(temp_out), sep = "\n")
+    Output
+      mpg|cyl|disp|hp|drat|wt|qsec|vs|am|gear|carb
+      21.0|6.0||||2.62|16.46|0.0|1.0|4.0|4.0
+      21.0|6.0|160.0|110.0|3.9|2.875|17.02|0.0|1.0|4.0|4.0
+      22.8|4.0||||2.32|18.61|1.0|1.0|4.0|1.0
+      21.4|6.0|258.0|110.0|3.08|3.215|19.44|1.0|0.0|3.0|1.0
+      18.7|8.0|360.0|175.0|3.15|3.44|17.02|0.0|0.0|3.0|2.0
+      18.1|6.0|225.0|105.0|2.76|3.46|20.22|1.0|0.0|3.0|1.0
+      14.3|8.0|360.0|245.0|3.21|3.57|15.84|0.0|0.0|3.0|4.0
+      24.4|4.0|146.7|62.0|3.69|3.19|20.0|1.0|0.0|4.0|2.0
+      22.8|4.0||||3.15|22.9|1.0|0.0|4.0|2.0
+      19.2|6.0|167.6|123.0|3.92|3.44|18.3|1.0|0.0|4.0|4.0
+      17.8|6.0|167.6|123.0|3.92|3.44|18.9|1.0|0.0|4.0|4.0
+      16.4|8.0||||4.07|17.4|0.0|0.0|3.0|3.0
+      17.3|8.0|275.8|180.0|3.07|3.73|17.6|0.0|0.0|3.0|3.0
+      15.2|8.0|275.8|180.0|3.07|3.78|18.0|0.0|0.0|3.0|3.0
+      10.4|8.0|472.0|205.0|2.93|5.25|17.98|0.0|0.0|3.0|4.0
+      10.4|8.0|460.0|215.0|3.0|5.424|17.82|0.0|0.0|3.0|4.0
+      14.7|8.0|440.0|230.0|3.23|5.345|17.42|0.0|0.0|3.0|4.0
+      32.4|4.0|78.7|66.0|4.08|2.2|19.47|1.0|1.0|4.0|1.0
+      30.4|4.0|75.7|52.0|4.93|1.615|18.52|1.0|1.0|4.0|2.0
+      33.9|4.0|71.1|65.0|4.22|1.835|19.9|1.0|1.0|4.0|1.0
+      21.5|4.0|120.1|97.0|3.7|2.465|20.01|1.0|0.0|3.0|1.0
+      15.5|8.0|318.0|150.0|2.76|3.52|16.87|0.0|0.0|3.0|2.0
+      15.2|8.0|304.0|150.0|3.15|3.435|17.3|0.0|0.0|3.0|2.0
+      13.3|8.0|350.0|245.0|3.73|3.84|15.41|0.0|0.0|3.0|4.0
+      19.2|8.0|400.0|175.0|3.08|3.845|17.05|0.0|0.0|3.0|2.0
+      27.3|4.0|79.0|66.0|4.08|1.935|18.9|1.0|1.0|4.0|1.0
+      26.0|4.0|120.3|91.0|4.43|2.14|16.7|0.0|1.0|5.0|2.0
+      30.4|4.0|95.1|113.0|3.77|1.513|16.9|1.0|1.0|5.0|2.0
+      15.8|8.0|351.0|264.0|4.22|3.17|14.5|0.0|1.0|5.0|4.0
+      19.7|6.0|145.0|175.0|3.62|2.77|15.5|0.0|1.0|5.0|6.0
+      15.0|8.0|301.0|335.0|3.54|3.57|14.6|0.0|1.0|5.0|8.0
+      21.4|4.0|121.0|109.0|4.11|2.78|18.6|1.0|1.0|4.0|2.0
+
+# write_csv: quote_style and quote works
+
+    Code
+      cat(readLines(temp_out), sep = "\n")
+    Output
+      +Sepal.Length+,+Sepal.Width+,+Petal.Length+,+Petal.Width+,+Species+
+      +5.1+,+3.5+,+1.4+,+0.2+,+setosa+
+      +4.9+,+3.0+,+1.4+,+0.2+,+setosa+
+      +4.7+,+3.2+,+1.3+,+0.2+,+setosa+
+      +4.6+,+3.1+,+1.5+,+0.2+,+setosa+
+      +5.0+,+3.6+,+1.4+,+0.2+,+setosa+
+      +5.4+,+3.9+,+1.7+,+0.4+,+setosa+
+      +4.6+,+3.4+,+1.4+,+0.3+,+setosa+
+      +5.0+,+3.4+,+1.5+,+0.2+,+setosa+
+      +4.4+,+2.9+,+1.4+,+0.2+,+setosa+
+      +4.9+,+3.1+,+1.5+,+0.1+,+setosa+
+      +5.4+,+3.7+,+1.5+,+0.2+,+setosa+
+      +4.8+,+3.4+,+1.6+,+0.2+,+setosa+
+      +4.8+,+3.0+,+1.4+,+0.1+,+setosa+
+      +4.3+,+3.0+,+1.1+,+0.1+,+setosa+
+      +5.8+,+4.0+,+1.2+,+0.2+,+setosa+
+      +5.7+,+4.4+,+1.5+,+0.4+,+setosa+
+      +5.4+,+3.9+,+1.3+,+0.4+,+setosa+
+      +5.1+,+3.5+,+1.4+,+0.3+,+setosa+
+      +5.7+,+3.8+,+1.7+,+0.3+,+setosa+
+      +5.1+,+3.8+,+1.5+,+0.3+,+setosa+
+      +5.4+,+3.4+,+1.7+,+0.2+,+setosa+
+      +5.1+,+3.7+,+1.5+,+0.4+,+setosa+
+      +4.6+,+3.6+,+1.0+,+0.2+,+setosa+
+      +5.1+,+3.3+,+1.7+,+0.5+,+setosa+
+      +4.8+,+3.4+,+1.9+,+0.2+,+setosa+
+      +5.0+,+3.0+,+1.6+,+0.2+,+setosa+
+      +5.0+,+3.4+,+1.6+,+0.4+,+setosa+
+      +5.2+,+3.5+,+1.5+,+0.2+,+setosa+
+      +5.2+,+3.4+,+1.4+,+0.2+,+setosa+
+      +4.7+,+3.2+,+1.6+,+0.2+,+setosa+
+      +4.8+,+3.1+,+1.6+,+0.2+,+setosa+
+      +5.4+,+3.4+,+1.5+,+0.4+,+setosa+
+      +5.2+,+4.1+,+1.5+,+0.1+,+setosa+
+      +5.5+,+4.2+,+1.4+,+0.2+,+setosa+
+      +4.9+,+3.1+,+1.5+,+0.2+,+setosa+
+      +5.0+,+3.2+,+1.2+,+0.2+,+setosa+
+      +5.5+,+3.5+,+1.3+,+0.2+,+setosa+
+      +4.9+,+3.6+,+1.4+,+0.1+,+setosa+
+      +4.4+,+3.0+,+1.3+,+0.2+,+setosa+
+      +5.1+,+3.4+,+1.5+,+0.2+,+setosa+
+      +5.0+,+3.5+,+1.3+,+0.3+,+setosa+
+      +4.5+,+2.3+,+1.3+,+0.3+,+setosa+
+      +4.4+,+3.2+,+1.3+,+0.2+,+setosa+
+      +5.0+,+3.5+,+1.6+,+0.6+,+setosa+
+      +5.1+,+3.8+,+1.9+,+0.4+,+setosa+
+      +4.8+,+3.0+,+1.4+,+0.3+,+setosa+
+      +5.1+,+3.8+,+1.6+,+0.2+,+setosa+
+      +4.6+,+3.2+,+1.4+,+0.2+,+setosa+
+      +5.3+,+3.7+,+1.5+,+0.2+,+setosa+
+      +5.0+,+3.3+,+1.4+,+0.2+,+setosa+
+      +7.0+,+3.2+,+4.7+,+1.4+,+versicolor+
+      +6.4+,+3.2+,+4.5+,+1.5+,+versicolor+
+      +6.9+,+3.1+,+4.9+,+1.5+,+versicolor+
+      +5.5+,+2.3+,+4.0+,+1.3+,+versicolor+
+      +6.5+,+2.8+,+4.6+,+1.5+,+versicolor+
+      +5.7+,+2.8+,+4.5+,+1.3+,+versicolor+
+      +6.3+,+3.3+,+4.7+,+1.6+,+versicolor+
+      +4.9+,+2.4+,+3.3+,+1.0+,+versicolor+
+      +6.6+,+2.9+,+4.6+,+1.3+,+versicolor+
+      +5.2+,+2.7+,+3.9+,+1.4+,+versicolor+
+      +5.0+,+2.0+,+3.5+,+1.0+,+versicolor+
+      +5.9+,+3.0+,+4.2+,+1.5+,+versicolor+
+      +6.0+,+2.2+,+4.0+,+1.0+,+versicolor+
+      +6.1+,+2.9+,+4.7+,+1.4+,+versicolor+
+      +5.6+,+2.9+,+3.6+,+1.3+,+versicolor+
+      +6.7+,+3.1+,+4.4+,+1.4+,+versicolor+
+      +5.6+,+3.0+,+4.5+,+1.5+,+versicolor+
+      +5.8+,+2.7+,+4.1+,+1.0+,+versicolor+
+      +6.2+,+2.2+,+4.5+,+1.5+,+versicolor+
+      +5.6+,+2.5+,+3.9+,+1.1+,+versicolor+
+      +5.9+,+3.2+,+4.8+,+1.8+,+versicolor+
+      +6.1+,+2.8+,+4.0+,+1.3+,+versicolor+
+      +6.3+,+2.5+,+4.9+,+1.5+,+versicolor+
+      +6.1+,+2.8+,+4.7+,+1.2+,+versicolor+
+      +6.4+,+2.9+,+4.3+,+1.3+,+versicolor+
+      +6.6+,+3.0+,+4.4+,+1.4+,+versicolor+
+      +6.8+,+2.8+,+4.8+,+1.4+,+versicolor+
+      +6.7+,+3.0+,+5.0+,+1.7+,+versicolor+
+      +6.0+,+2.9+,+4.5+,+1.5+,+versicolor+
+      +5.7+,+2.6+,+3.5+,+1.0+,+versicolor+
+      +5.5+,+2.4+,+3.8+,+1.1+,+versicolor+
+      +5.5+,+2.4+,+3.7+,+1.0+,+versicolor+
+      +5.8+,+2.7+,+3.9+,+1.2+,+versicolor+
+      +6.0+,+2.7+,+5.1+,+1.6+,+versicolor+
+      +5.4+,+3.0+,+4.5+,+1.5+,+versicolor+
+      +6.0+,+3.4+,+4.5+,+1.6+,+versicolor+
+      +6.7+,+3.1+,+4.7+,+1.5+,+versicolor+
+      +6.3+,+2.3+,+4.4+,+1.3+,+versicolor+
+      +5.6+,+3.0+,+4.1+,+1.3+,+versicolor+
+      +5.5+,+2.5+,+4.0+,+1.3+,+versicolor+
+      +5.5+,+2.6+,+4.4+,+1.2+,+versicolor+
+      +6.1+,+3.0+,+4.6+,+1.4+,+versicolor+
+      +5.8+,+2.6+,+4.0+,+1.2+,+versicolor+
+      +5.0+,+2.3+,+3.3+,+1.0+,+versicolor+
+      +5.6+,+2.7+,+4.2+,+1.3+,+versicolor+
+      +5.7+,+3.0+,+4.2+,+1.2+,+versicolor+
+      +5.7+,+2.9+,+4.2+,+1.3+,+versicolor+
+      +6.2+,+2.9+,+4.3+,+1.3+,+versicolor+
+      +5.1+,+2.5+,+3.0+,+1.1+,+versicolor+
+      +5.7+,+2.8+,+4.1+,+1.3+,+versicolor+
+      +6.3+,+3.3+,+6.0+,+2.5+,+virginica+
+      +5.8+,+2.7+,+5.1+,+1.9+,+virginica+
+      +7.1+,+3.0+,+5.9+,+2.1+,+virginica+
+      +6.3+,+2.9+,+5.6+,+1.8+,+virginica+
+      +6.5+,+3.0+,+5.8+,+2.2+,+virginica+
+      +7.6+,+3.0+,+6.6+,+2.1+,+virginica+
+      +4.9+,+2.5+,+4.5+,+1.7+,+virginica+
+      +7.3+,+2.9+,+6.3+,+1.8+,+virginica+
+      +6.7+,+2.5+,+5.8+,+1.8+,+virginica+
+      +7.2+,+3.6+,+6.1+,+2.5+,+virginica+
+      +6.5+,+3.2+,+5.1+,+2.0+,+virginica+
+      +6.4+,+2.7+,+5.3+,+1.9+,+virginica+
+      +6.8+,+3.0+,+5.5+,+2.1+,+virginica+
+      +5.7+,+2.5+,+5.0+,+2.0+,+virginica+
+      +5.8+,+2.8+,+5.1+,+2.4+,+virginica+
+      +6.4+,+3.2+,+5.3+,+2.3+,+virginica+
+      +6.5+,+3.0+,+5.5+,+1.8+,+virginica+
+      +7.7+,+3.8+,+6.7+,+2.2+,+virginica+
+      +7.7+,+2.6+,+6.9+,+2.3+,+virginica+
+      +6.0+,+2.2+,+5.0+,+1.5+,+virginica+
+      +6.9+,+3.2+,+5.7+,+2.3+,+virginica+
+      +5.6+,+2.8+,+4.9+,+2.0+,+virginica+
+      +7.7+,+2.8+,+6.7+,+2.0+,+virginica+
+      +6.3+,+2.7+,+4.9+,+1.8+,+virginica+
+      +6.7+,+3.3+,+5.7+,+2.1+,+virginica+
+      +7.2+,+3.2+,+6.0+,+1.8+,+virginica+
+      +6.2+,+2.8+,+4.8+,+1.8+,+virginica+
+      +6.1+,+3.0+,+4.9+,+1.8+,+virginica+
+      +6.4+,+2.8+,+5.6+,+2.1+,+virginica+
+      +7.2+,+3.0+,+5.8+,+1.6+,+virginica+
+      +7.4+,+2.8+,+6.1+,+1.9+,+virginica+
+      +7.9+,+3.8+,+6.4+,+2.0+,+virginica+
+      +6.4+,+2.8+,+5.6+,+2.2+,+virginica+
+      +6.3+,+2.8+,+5.1+,+1.5+,+virginica+
+      +6.1+,+2.6+,+5.6+,+1.4+,+virginica+
+      +7.7+,+3.0+,+6.1+,+2.3+,+virginica+
+      +6.3+,+3.4+,+5.6+,+2.4+,+virginica+
+      +6.4+,+3.1+,+5.5+,+1.8+,+virginica+
+      +6.0+,+3.0+,+4.8+,+1.8+,+virginica+
+      +6.9+,+3.1+,+5.4+,+2.1+,+virginica+
+      +6.7+,+3.1+,+5.6+,+2.4+,+virginica+
+      +6.9+,+3.1+,+5.1+,+2.3+,+virginica+
+      +5.8+,+2.7+,+5.1+,+1.9+,+virginica+
+      +6.8+,+3.2+,+5.9+,+2.3+,+virginica+
+      +6.7+,+3.3+,+5.7+,+2.5+,+virginica+
+      +6.7+,+3.0+,+5.2+,+2.3+,+virginica+
+      +6.3+,+2.5+,+5.0+,+1.9+,+virginica+
+      +6.5+,+3.0+,+5.2+,+2.0+,+virginica+
+      +6.2+,+3.4+,+5.4+,+2.3+,+virginica+
+      +5.9+,+3.0+,+5.1+,+1.8+,+virginica+
+
+---
+
+    Code
+      cat(readLines(temp_out), sep = "\n")
+    Output
+      +Sepal.Length+,+Sepal.Width+,+Petal.Length+,+Petal.Width+,+Species+
+      5.1,3.5,1.4,0.2,+setosa+
+      4.9,3.0,1.4,0.2,+setosa+
+      4.7,3.2,1.3,0.2,+setosa+
+      4.6,3.1,1.5,0.2,+setosa+
+      5.0,3.6,1.4,0.2,+setosa+
+      5.4,3.9,1.7,0.4,+setosa+
+      4.6,3.4,1.4,0.3,+setosa+
+      5.0,3.4,1.5,0.2,+setosa+
+      4.4,2.9,1.4,0.2,+setosa+
+      4.9,3.1,1.5,0.1,+setosa+
+      5.4,3.7,1.5,0.2,+setosa+
+      4.8,3.4,1.6,0.2,+setosa+
+      4.8,3.0,1.4,0.1,+setosa+
+      4.3,3.0,1.1,0.1,+setosa+
+      5.8,4.0,1.2,0.2,+setosa+
+      5.7,4.4,1.5,0.4,+setosa+
+      5.4,3.9,1.3,0.4,+setosa+
+      5.1,3.5,1.4,0.3,+setosa+
+      5.7,3.8,1.7,0.3,+setosa+
+      5.1,3.8,1.5,0.3,+setosa+
+      5.4,3.4,1.7,0.2,+setosa+
+      5.1,3.7,1.5,0.4,+setosa+
+      4.6,3.6,1.0,0.2,+setosa+
+      5.1,3.3,1.7,0.5,+setosa+
+      4.8,3.4,1.9,0.2,+setosa+
+      5.0,3.0,1.6,0.2,+setosa+
+      5.0,3.4,1.6,0.4,+setosa+
+      5.2,3.5,1.5,0.2,+setosa+
+      5.2,3.4,1.4,0.2,+setosa+
+      4.7,3.2,1.6,0.2,+setosa+
+      4.8,3.1,1.6,0.2,+setosa+
+      5.4,3.4,1.5,0.4,+setosa+
+      5.2,4.1,1.5,0.1,+setosa+
+      5.5,4.2,1.4,0.2,+setosa+
+      4.9,3.1,1.5,0.2,+setosa+
+      5.0,3.2,1.2,0.2,+setosa+
+      5.5,3.5,1.3,0.2,+setosa+
+      4.9,3.6,1.4,0.1,+setosa+
+      4.4,3.0,1.3,0.2,+setosa+
+      5.1,3.4,1.5,0.2,+setosa+
+      5.0,3.5,1.3,0.3,+setosa+
+      4.5,2.3,1.3,0.3,+setosa+
+      4.4,3.2,1.3,0.2,+setosa+
+      5.0,3.5,1.6,0.6,+setosa+
+      5.1,3.8,1.9,0.4,+setosa+
+      4.8,3.0,1.4,0.3,+setosa+
+      5.1,3.8,1.6,0.2,+setosa+
+      4.6,3.2,1.4,0.2,+setosa+
+      5.3,3.7,1.5,0.2,+setosa+
+      5.0,3.3,1.4,0.2,+setosa+
+      7.0,3.2,4.7,1.4,+versicolor+
+      6.4,3.2,4.5,1.5,+versicolor+
+      6.9,3.1,4.9,1.5,+versicolor+
+      5.5,2.3,4.0,1.3,+versicolor+
+      6.5,2.8,4.6,1.5,+versicolor+
+      5.7,2.8,4.5,1.3,+versicolor+
+      6.3,3.3,4.7,1.6,+versicolor+
+      4.9,2.4,3.3,1.0,+versicolor+
+      6.6,2.9,4.6,1.3,+versicolor+
+      5.2,2.7,3.9,1.4,+versicolor+
+      5.0,2.0,3.5,1.0,+versicolor+
+      5.9,3.0,4.2,1.5,+versicolor+
+      6.0,2.2,4.0,1.0,+versicolor+
+      6.1,2.9,4.7,1.4,+versicolor+
+      5.6,2.9,3.6,1.3,+versicolor+
+      6.7,3.1,4.4,1.4,+versicolor+
+      5.6,3.0,4.5,1.5,+versicolor+
+      5.8,2.7,4.1,1.0,+versicolor+
+      6.2,2.2,4.5,1.5,+versicolor+
+      5.6,2.5,3.9,1.1,+versicolor+
+      5.9,3.2,4.8,1.8,+versicolor+
+      6.1,2.8,4.0,1.3,+versicolor+
+      6.3,2.5,4.9,1.5,+versicolor+
+      6.1,2.8,4.7,1.2,+versicolor+
+      6.4,2.9,4.3,1.3,+versicolor+
+      6.6,3.0,4.4,1.4,+versicolor+
+      6.8,2.8,4.8,1.4,+versicolor+
+      6.7,3.0,5.0,1.7,+versicolor+
+      6.0,2.9,4.5,1.5,+versicolor+
+      5.7,2.6,3.5,1.0,+versicolor+
+      5.5,2.4,3.8,1.1,+versicolor+
+      5.5,2.4,3.7,1.0,+versicolor+
+      5.8,2.7,3.9,1.2,+versicolor+
+      6.0,2.7,5.1,1.6,+versicolor+
+      5.4,3.0,4.5,1.5,+versicolor+
+      6.0,3.4,4.5,1.6,+versicolor+
+      6.7,3.1,4.7,1.5,+versicolor+
+      6.3,2.3,4.4,1.3,+versicolor+
+      5.6,3.0,4.1,1.3,+versicolor+
+      5.5,2.5,4.0,1.3,+versicolor+
+      5.5,2.6,4.4,1.2,+versicolor+
+      6.1,3.0,4.6,1.4,+versicolor+
+      5.8,2.6,4.0,1.2,+versicolor+
+      5.0,2.3,3.3,1.0,+versicolor+
+      5.6,2.7,4.2,1.3,+versicolor+
+      5.7,3.0,4.2,1.2,+versicolor+
+      5.7,2.9,4.2,1.3,+versicolor+
+      6.2,2.9,4.3,1.3,+versicolor+
+      5.1,2.5,3.0,1.1,+versicolor+
+      5.7,2.8,4.1,1.3,+versicolor+
+      6.3,3.3,6.0,2.5,+virginica+
+      5.8,2.7,5.1,1.9,+virginica+
+      7.1,3.0,5.9,2.1,+virginica+
+      6.3,2.9,5.6,1.8,+virginica+
+      6.5,3.0,5.8,2.2,+virginica+
+      7.6,3.0,6.6,2.1,+virginica+
+      4.9,2.5,4.5,1.7,+virginica+
+      7.3,2.9,6.3,1.8,+virginica+
+      6.7,2.5,5.8,1.8,+virginica+
+      7.2,3.6,6.1,2.5,+virginica+
+      6.5,3.2,5.1,2.0,+virginica+
+      6.4,2.7,5.3,1.9,+virginica+
+      6.8,3.0,5.5,2.1,+virginica+
+      5.7,2.5,5.0,2.0,+virginica+
+      5.8,2.8,5.1,2.4,+virginica+
+      6.4,3.2,5.3,2.3,+virginica+
+      6.5,3.0,5.5,1.8,+virginica+
+      7.7,3.8,6.7,2.2,+virginica+
+      7.7,2.6,6.9,2.3,+virginica+
+      6.0,2.2,5.0,1.5,+virginica+
+      6.9,3.2,5.7,2.3,+virginica+
+      5.6,2.8,4.9,2.0,+virginica+
+      7.7,2.8,6.7,2.0,+virginica+
+      6.3,2.7,4.9,1.8,+virginica+
+      6.7,3.3,5.7,2.1,+virginica+
+      7.2,3.2,6.0,1.8,+virginica+
+      6.2,2.8,4.8,1.8,+virginica+
+      6.1,3.0,4.9,1.8,+virginica+
+      6.4,2.8,5.6,2.1,+virginica+
+      7.2,3.0,5.8,1.6,+virginica+
+      7.4,2.8,6.1,1.9,+virginica+
+      7.9,3.8,6.4,2.0,+virginica+
+      6.4,2.8,5.6,2.2,+virginica+
+      6.3,2.8,5.1,1.5,+virginica+
+      6.1,2.6,5.6,1.4,+virginica+
+      7.7,3.0,6.1,2.3,+virginica+
+      6.3,3.4,5.6,2.4,+virginica+
+      6.4,3.1,5.5,1.8,+virginica+
+      6.0,3.0,4.8,1.8,+virginica+
+      6.9,3.1,5.4,2.1,+virginica+
+      6.7,3.1,5.6,2.4,+virginica+
+      6.9,3.1,5.1,2.3,+virginica+
+      5.8,2.7,5.1,1.9,+virginica+
+      6.8,3.2,5.9,2.3,+virginica+
+      6.7,3.3,5.7,2.5,+virginica+
+      6.7,3.0,5.2,2.3,+virginica+
+      6.3,2.5,5.0,1.9,+virginica+
+      6.5,3.0,5.2,2.0,+virginica+
+      6.2,3.4,5.4,2.3,+virginica+
+      5.9,3.0,5.1,1.8,+virginica+
+
diff --git a/tests/testthat/test-csv.R b/tests/testthat/test-csv.R
index 6e2c69469..ac02b8cf5 100644
--- a/tests/testthat/test-csv.R
+++ b/tests/testthat/test-csv.R
@@ -49,19 +49,13 @@ test_that("write_csv: null_values works", {
     dat_pl$write_csv(temp_out, null_values = NULL)
   )
   dat_pl$write_csv(temp_out, null_values = "hello")
-  tmp = pl$read_csv(temp_out)$to_data_frame()
-  expect_true(is.character(tmp$disp) && is.character(tmp$hp) && is.character(tmp$drat))
-  expect_equal(tmp[1:2, "disp"], c("hello", "160.0"))
+  expect_snapshot(readLines(temp_out) |> cat(sep = "\n"))
 })
 
 
 test_that("write_csv: separator works", {
   dat_pl$write_csv(temp_out, separator = "|")
-  expect_identical(
-    pl$read_csv(temp_out, sep = "|")$to_data_frame(),
-    dat,
-    ignore_attr = TRUE # rownames are lost when writing / reading from CSV
-  )
+  expect_snapshot(readLines(temp_out) |> cat(sep = "\n"))
 })
 
 test_that("write_csv: quote_style and quote works", {
@@ -73,18 +67,8 @@ test_that("write_csv: quote_style and quote works", {
   )
 
   dat_pl2$write_csv(temp_out, quote_style = "always", quote = "+")
-  expect_identical(
-    head(pl$read_csv(temp_out)$to_data_frame()[["+Sepal.Length+"]], n = 2),
-    c("+5.1+", "+4.9+")
-  )
+  expect_snapshot(readLines(temp_out) |> cat(sep = "\n"))
 
   dat_pl2$write_csv(temp_out, quote_style = "non_numeric", quote = "+")
-  expect_identical(
-    head(pl$read_csv(temp_out)$to_data_frame()[["+Sepal.Length+"]], n = 2),
-    c(5.1, 4.9)
-  )
-  expect_identical(
-    head(pl$read_csv(temp_out)$to_data_frame()[["+Species+"]], n = 2),
-    c("+setosa+", "+setosa+")
-  )
+  expect_snapshot(readLines(temp_out) |> cat(sep = "\n"))
 })

From ab4253fc31d3481885518ed54d621cf2d6320e1a Mon Sep 17 00:00:00 2001
From: eitsupi <ts1s1andn@gmail.com>
Date: Mon, 16 Oct 2023 14:40:18 +0000
Subject: [PATCH 09/25] docs: fix typo

---
 R/dataframe__frame.R | 2 +-
 man/IO_write_csv.Rd  | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/R/dataframe__frame.R b/R/dataframe__frame.R
index ac82cd991..edefe5247 100644
--- a/R/dataframe__frame.R
+++ b/R/dataframe__frame.R
@@ -1704,7 +1704,7 @@ DataFrame_sample = function(
 #' @param null_values A string representing null values (defaulting to the empty
 #' string).
 #' @param quote_style Determines the quoting strategy used.
-#' * "`necessary"` (default): This puts quotes around fields only when necessary.
+#' * `"necessary"` (default): This puts quotes around fields only when necessary.
 #'   They are necessary when fields contain a quote, delimiter or record
 #'   terminator. Quotes are also necessary when writing an empty record (which
 #'   is indistinguishable from a record with one empty field). This is the
diff --git a/man/IO_write_csv.Rd b/man/IO_write_csv.Rd
index d20dee475..0d2cca41d 100644
--- a/man/IO_write_csv.Rd
+++ b/man/IO_write_csv.Rd
@@ -51,7 +51,7 @@ string).}
 
 \item{quote_style}{Determines the quoting strategy used.
 \itemize{
-\item "\verb{necessary"} (default): This puts quotes around fields only when necessary.
+\item \code{"necessary"} (default): This puts quotes around fields only when necessary.
 They are necessary when fields contain a quote, delimiter or record
 terminator. Quotes are also necessary when writing an empty record (which
 is indistinguishable from a record with one empty field). This is the

From d4ab52c127cfd483983ad1cca6020e7ff4c08617 Mon Sep 17 00:00:00 2001
From: eitsupi <ts1s1andn@gmail.com>
Date: Mon, 16 Oct 2023 14:46:12 +0000
Subject: [PATCH 10/25] refactor(test): use helper function

---
 tests/testthat/_snaps/csv.md | 8 ++++----
 tests/testthat/helper.R      | 4 ++++
 tests/testthat/test-csv.R    | 8 ++++----
 3 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/tests/testthat/_snaps/csv.md b/tests/testthat/_snaps/csv.md
index 4cde591fe..1f81d03b9 100644
--- a/tests/testthat/_snaps/csv.md
+++ b/tests/testthat/_snaps/csv.md
@@ -1,7 +1,7 @@
 # write_csv: null_values works
 
     Code
-      cat(readLines(temp_out), sep = "\n")
+      cat(readLines(path), sep = "\n")
     Output
       mpg,cyl,disp,hp,drat,wt,qsec,vs,am,gear,carb
       21.0,6.0,hello,hello,hello,2.62,16.46,0.0,1.0,4.0,4.0
@@ -40,7 +40,7 @@
 # write_csv: separator works
 
     Code
-      cat(readLines(temp_out), sep = "\n")
+      cat(readLines(path), sep = "\n")
     Output
       mpg|cyl|disp|hp|drat|wt|qsec|vs|am|gear|carb
       21.0|6.0||||2.62|16.46|0.0|1.0|4.0|4.0
@@ -79,7 +79,7 @@
 # write_csv: quote_style and quote works
 
     Code
-      cat(readLines(temp_out), sep = "\n")
+      cat(readLines(path), sep = "\n")
     Output
       +Sepal.Length+,+Sepal.Width+,+Petal.Length+,+Petal.Width+,+Species+
       +5.1+,+3.5+,+1.4+,+0.2+,+setosa+
@@ -236,7 +236,7 @@
 ---
 
     Code
-      cat(readLines(temp_out), sep = "\n")
+      cat(readLines(path), sep = "\n")
     Output
       +Sepal.Length+,+Sepal.Width+,+Petal.Length+,+Petal.Width+,+Species+
       5.1,3.5,1.4,0.2,+setosa+
diff --git a/tests/testthat/helper.R b/tests/testthat/helper.R
index 5c4e3a460..73325813c 100644
--- a/tests/testthat/helper.R
+++ b/tests/testthat/helper.R
@@ -84,3 +84,7 @@ expect_rpolarserr = function(expr, ctxs) {
   expect_identical(class(res$err), "RPolarsErr")
   expect_identical(names(res$err$contexts()), ctxs)
 }
+
+expect_snapshot_file = function(path, ...) {
+  expect_snapshot(readLines(path) |> cat(sep = "\n"), ...)
+}
diff --git a/tests/testthat/test-csv.R b/tests/testthat/test-csv.R
index ac02b8cf5..802c01b9b 100644
--- a/tests/testthat/test-csv.R
+++ b/tests/testthat/test-csv.R
@@ -49,13 +49,13 @@ test_that("write_csv: null_values works", {
     dat_pl$write_csv(temp_out, null_values = NULL)
   )
   dat_pl$write_csv(temp_out, null_values = "hello")
-  expect_snapshot(readLines(temp_out) |> cat(sep = "\n"))
+  expect_snapshot_file(temp_out)
 })
 
 
 test_that("write_csv: separator works", {
   dat_pl$write_csv(temp_out, separator = "|")
-  expect_snapshot(readLines(temp_out) |> cat(sep = "\n"))
+  expect_snapshot_file(temp_out)
 })
 
 test_that("write_csv: quote_style and quote works", {
@@ -67,8 +67,8 @@ test_that("write_csv: quote_style and quote works", {
   )
 
   dat_pl2$write_csv(temp_out, quote_style = "always", quote = "+")
-  expect_snapshot(readLines(temp_out) |> cat(sep = "\n"))
+  expect_snapshot_file(temp_out)
 
   dat_pl2$write_csv(temp_out, quote_style = "non_numeric", quote = "+")
-  expect_snapshot(readLines(temp_out) |> cat(sep = "\n"))
+  expect_snapshot_file(temp_out)
 })

From a0b661dd1ab2a1d6ecf36a5419fe8d9b38d6a1c6 Mon Sep 17 00:00:00 2001
From: eitsupi <ts1s1andn@gmail.com>
Date: Mon, 16 Oct 2023 14:59:20 +0000
Subject: [PATCH 11/25] test: tests for quote_style

---
 tests/testthat/test-csv.R | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/tests/testthat/test-csv.R b/tests/testthat/test-csv.R
index 802c01b9b..09b4fd5ad 100644
--- a/tests/testthat/test-csv.R
+++ b/tests/testthat/test-csv.R
@@ -72,3 +72,15 @@ test_that("write_csv: quote_style and quote works", {
   dat_pl2$write_csv(temp_out, quote_style = "non_numeric", quote = "+")
   expect_snapshot_file(temp_out)
 })
+
+patrick::with_parameters_test_that(
+  "write_csv: quote_style",
+  {
+    df = pl$DataFrame(
+      a = c(r"("foo")", "bar"),
+      b = 1:2,
+      c = letters[1:2]
+    )$write_csv(temp_out, quote_style = quote_style)
+  },
+  quote_style = c("necessary", "always", "non_numeric")
+)

From ada992b0a166e3e226fd9e719d706b17d10ce16e Mon Sep 17 00:00:00 2001
From: Etienne Bacher <52219252+etiennebacher@users.noreply.github.com>
Date: Mon, 16 Oct 2023 18:46:08 +0200
Subject: [PATCH 12/25] remove check for path on the R side

---
 R/dataframe__frame.R | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/R/dataframe__frame.R b/R/dataframe__frame.R
index edefe5247..e82baae9b 100644
--- a/R/dataframe__frame.R
+++ b/R/dataframe__frame.R
@@ -1742,10 +1742,6 @@ DataFrame_write_csv = function(
     quote_style = "necessary"
 ) {
 
-  if (file_ext(path) != "csv") {
-    stop("Argument `path` must the path to a CSV file.")
-  }
-
   if (length(quote_style) == 0 ||
       !quote_style %in% c("always", "necessary", "non_numeric")) {
     stop("Argument `quote_style` must be one of 'always', 'necessary', or 'non_numeric'.")

From 502501786ba9becc38244f8d081fdac5b1a64a70 Mon Sep 17 00:00:00 2001
From: Etienne Bacher <52219252+etiennebacher@users.noreply.github.com>
Date: Mon, 16 Oct 2023 18:52:40 +0200
Subject: [PATCH 13/25] update tests

---
 tests/testthat/_snaps/csv.md | 61 ++++++++++++++++--------------------
 tests/testthat/test-csv.R    |  8 ++---
 2 files changed, 29 insertions(+), 40 deletions(-)

diff --git a/tests/testthat/_snaps/csv.md b/tests/testthat/_snaps/csv.md
index 1f81d03b9..33b856e36 100644
--- a/tests/testthat/_snaps/csv.md
+++ b/tests/testthat/_snaps/csv.md
@@ -19,23 +19,6 @@
       17.3,8.0,275.8,180.0,3.07,3.73,17.6,0.0,0.0,3.0,3.0
       15.2,8.0,275.8,180.0,3.07,3.78,18.0,0.0,0.0,3.0,3.0
       10.4,8.0,472.0,205.0,2.93,5.25,17.98,0.0,0.0,3.0,4.0
-      10.4,8.0,460.0,215.0,3.0,5.424,17.82,0.0,0.0,3.0,4.0
-      14.7,8.0,440.0,230.0,3.23,5.345,17.42,0.0,0.0,3.0,4.0
-      32.4,4.0,78.7,66.0,4.08,2.2,19.47,1.0,1.0,4.0,1.0
-      30.4,4.0,75.7,52.0,4.93,1.615,18.52,1.0,1.0,4.0,2.0
-      33.9,4.0,71.1,65.0,4.22,1.835,19.9,1.0,1.0,4.0,1.0
-      21.5,4.0,120.1,97.0,3.7,2.465,20.01,1.0,0.0,3.0,1.0
-      15.5,8.0,318.0,150.0,2.76,3.52,16.87,0.0,0.0,3.0,2.0
-      15.2,8.0,304.0,150.0,3.15,3.435,17.3,0.0,0.0,3.0,2.0
-      13.3,8.0,350.0,245.0,3.73,3.84,15.41,0.0,0.0,3.0,4.0
-      19.2,8.0,400.0,175.0,3.08,3.845,17.05,0.0,0.0,3.0,2.0
-      27.3,4.0,79.0,66.0,4.08,1.935,18.9,1.0,1.0,4.0,1.0
-      26.0,4.0,120.3,91.0,4.43,2.14,16.7,0.0,1.0,5.0,2.0
-      30.4,4.0,95.1,113.0,3.77,1.513,16.9,1.0,1.0,5.0,2.0
-      15.8,8.0,351.0,264.0,4.22,3.17,14.5,0.0,1.0,5.0,4.0
-      19.7,6.0,145.0,175.0,3.62,2.77,15.5,0.0,1.0,5.0,6.0
-      15.0,8.0,301.0,335.0,3.54,3.57,14.6,0.0,1.0,5.0,8.0
-      21.4,4.0,121.0,109.0,4.11,2.78,18.6,1.0,1.0,4.0,2.0
 
 # write_csv: separator works
 
@@ -58,23 +41,6 @@
       17.3|8.0|275.8|180.0|3.07|3.73|17.6|0.0|0.0|3.0|3.0
       15.2|8.0|275.8|180.0|3.07|3.78|18.0|0.0|0.0|3.0|3.0
       10.4|8.0|472.0|205.0|2.93|5.25|17.98|0.0|0.0|3.0|4.0
-      10.4|8.0|460.0|215.0|3.0|5.424|17.82|0.0|0.0|3.0|4.0
-      14.7|8.0|440.0|230.0|3.23|5.345|17.42|0.0|0.0|3.0|4.0
-      32.4|4.0|78.7|66.0|4.08|2.2|19.47|1.0|1.0|4.0|1.0
-      30.4|4.0|75.7|52.0|4.93|1.615|18.52|1.0|1.0|4.0|2.0
-      33.9|4.0|71.1|65.0|4.22|1.835|19.9|1.0|1.0|4.0|1.0
-      21.5|4.0|120.1|97.0|3.7|2.465|20.01|1.0|0.0|3.0|1.0
-      15.5|8.0|318.0|150.0|2.76|3.52|16.87|0.0|0.0|3.0|2.0
-      15.2|8.0|304.0|150.0|3.15|3.435|17.3|0.0|0.0|3.0|2.0
-      13.3|8.0|350.0|245.0|3.73|3.84|15.41|0.0|0.0|3.0|4.0
-      19.2|8.0|400.0|175.0|3.08|3.845|17.05|0.0|0.0|3.0|2.0
-      27.3|4.0|79.0|66.0|4.08|1.935|18.9|1.0|1.0|4.0|1.0
-      26.0|4.0|120.3|91.0|4.43|2.14|16.7|0.0|1.0|5.0|2.0
-      30.4|4.0|95.1|113.0|3.77|1.513|16.9|1.0|1.0|5.0|2.0
-      15.8|8.0|351.0|264.0|4.22|3.17|14.5|0.0|1.0|5.0|4.0
-      19.7|6.0|145.0|175.0|3.62|2.77|15.5|0.0|1.0|5.0|6.0
-      15.0|8.0|301.0|335.0|3.54|3.57|14.6|0.0|1.0|5.0|8.0
-      21.4|4.0|121.0|109.0|4.11|2.78|18.6|1.0|1.0|4.0|2.0
 
 # write_csv: quote_style and quote works
 
@@ -390,3 +356,30 @@
       6.2,3.4,5.4,2.3,+virginica+
       5.9,3.0,5.1,1.8,+virginica+
 
+# write_csv: quote_style quote_style=necessary
+
+    Code
+      cat(readLines(path), sep = "\n")
+    Output
+      a,b,c
+      """foo""",1,a
+      bar,2,b
+
+# write_csv: quote_style quote_style=always
+
+    Code
+      cat(readLines(path), sep = "\n")
+    Output
+      "a","b","c"
+      """foo""","1","a"
+      "bar","2","b"
+
+# write_csv: quote_style quote_style=non_numeric
+
+    Code
+      cat(readLines(path), sep = "\n")
+    Output
+      "a","b","c"
+      """foo""",1,"a"
+      "bar",2,"b"
+
diff --git a/tests/testthat/test-csv.R b/tests/testthat/test-csv.R
index 09b4fd5ad..601dc5e56 100644
--- a/tests/testthat/test-csv.R
+++ b/tests/testthat/test-csv.R
@@ -24,18 +24,13 @@ test_that("csv read iris", {
 })
 
 
-dat = mtcars
+dat = head(mtcars, n = 15)
 dat[c(1, 3, 9, 12), c(3, 4, 5)] = NA
 dat_pl = pl$DataFrame(dat)
 temp_noext = tempfile()
 temp_out = tempfile(fileext = ".csv")
 
 test_that("write_csv: path works", {
-  expect_error(
-    dat_pl$write_csv(temp_noext),
-    "must the path to a CSV file"
-  )
-
   dat_pl$write_csv(temp_out)
   expect_identical(
     pl$read_csv(temp_out)$to_data_frame(),
@@ -81,6 +76,7 @@ patrick::with_parameters_test_that(
       b = 1:2,
       c = letters[1:2]
     )$write_csv(temp_out, quote_style = quote_style)
+    expect_snapshot_file(temp_out)
   },
   quote_style = c("necessary", "always", "non_numeric")
 )

From dee44026093e3959b9547fa401a8db24c481e89c Mon Sep 17 00:00:00 2001
From: Etienne Bacher <52219252+etiennebacher@users.noreply.github.com>
Date: Mon, 16 Oct 2023 18:54:28 +0200
Subject: [PATCH 14/25] bump news

---
 NEWS.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/NEWS.md b/NEWS.md
index 2271b2f1c..1b499ea42 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -44,6 +44,7 @@
 - New function `pl$raw_list` and class `rpolars_raw_list` a list of R Raw's, where missing is
   encoded as `NULL` to aid conversion to polars binary Series. Support back and forth conversion
   from polars binary literal and Series to R raw (#417).
+- New method `$write_csv()` for `DataFrame` (#414).
 
 # polars 0.8.1
 

From 460bf3b51156c70d955238e7da7926fbab5b95a3 Mon Sep 17 00:00:00 2001
From: Etienne Bacher <52219252+etiennebacher@users.noreply.github.com>
Date: Tue, 17 Oct 2023 13:30:30 +0200
Subject: [PATCH 15/25] add some tests for date_format, time_format and
 datetime_format

---
 tests/testthat/_snaps/csv.md | 46 ++++++++++++++++++++++++++++++++++++
 tests/testthat/test-csv.R    | 41 ++++++++++++++++++++++++++++++++
 2 files changed, 87 insertions(+)

diff --git a/tests/testthat/_snaps/csv.md b/tests/testthat/_snaps/csv.md
index 33b856e36..308f03186 100644
--- a/tests/testthat/_snaps/csv.md
+++ b/tests/testthat/_snaps/csv.md
@@ -383,3 +383,49 @@
       """foo""",1,"a"
       "bar",2,"b"
 
+# write_csv: date_format works
+
+    Code
+      cat(readLines(path), sep = "\n")
+    Output
+      date
+      2020
+      2021
+      2022
+      2023
+
+---
+
+    Code
+      cat(readLines(path), sep = "\n")
+    Output
+      date
+      01/01/2020
+      01/01/2021
+      01/01/2022
+      01/01/2023
+
+# write_csv: datetime_format works
+
+    Code
+      cat(readLines(path), sep = "\n")
+    Output
+      date
+      00h00m - 01/01/2020
+      06h00m - 01/01/2020
+      12h00m - 01/01/2020
+      18h00m - 01/01/2020
+      00h00m - 02/01/2020
+
+# write_csv: time_format works
+
+    Code
+      cat(readLines(path), sep = "\n")
+    Output
+      date
+      2023-10-16T22:00:00.000000
+      2023-10-16T22:15:00.000000
+      2023-10-16T22:30:00.000000
+      2023-10-16T22:45:00.000000
+      2023-10-16T23:00:00.000000
+
diff --git a/tests/testthat/test-csv.R b/tests/testthat/test-csv.R
index 601dc5e56..3dd9e1b66 100644
--- a/tests/testthat/test-csv.R
+++ b/tests/testthat/test-csv.R
@@ -80,3 +80,44 @@ patrick::with_parameters_test_that(
   },
   quote_style = c("necessary", "always", "non_numeric")
 )
+
+test_that("write_csv: date_format works", {
+  dat <- pl$DataFrame(
+    date = pl$date_range(
+      as.Date("2020-01-01"),
+      as.Date("2023-01-02"),
+      interval = "1y",
+      eager = TRUE
+    )
+  )
+  dat$write_csv(temp_out, date_format = "%Y")
+  expect_snapshot_file(temp_out)
+  dat$write_csv(temp_out, date_format = "%d/%m/%Y")
+  expect_snapshot_file(temp_out)
+})
+
+test_that("write_csv: datetime_format works", {
+  dat <- pl$DataFrame(
+    date = pl$date_range(
+      as.Date("2020-01-01"),
+      as.Date("2020-01-02"),
+      interval = "6h",
+      eager = TRUE
+    )
+  )
+  dat$write_csv(temp_out, datetime_format = "%Hh%Mm - %d/%m/%Y")
+  expect_snapshot_file(temp_out)
+})
+
+test_that("write_csv: time_format works", {
+  dat <- pl$DataFrame(
+    date = pl$date_range(
+      strptime("00:00:00", format = "%H:%M:%S"),
+      strptime("01:00:00", format = "%H:%M:%S"),
+      interval = "15m",
+      eager = TRUE
+    )
+  )
+  dat$write_csv(temp_out, time_format = "%Hh%Mm%%Ss")
+  expect_snapshot_file(temp_out)
+})

From 8a554498eb6b7d20047fc3614ab1d649ea4cbf4a Mon Sep 17 00:00:00 2001
From: Etienne Bacher <52219252+etiennebacher@users.noreply.github.com>
Date: Tue, 17 Oct 2023 13:32:45 +0200
Subject: [PATCH 16/25] test float_precision

---
 tests/testthat/_snaps/csv.md | 18 ++++++++++++++++++
 tests/testthat/test-csv.R    | 10 ++++++++++
 2 files changed, 28 insertions(+)

diff --git a/tests/testthat/_snaps/csv.md b/tests/testthat/_snaps/csv.md
index 308f03186..fbfd5d01c 100644
--- a/tests/testthat/_snaps/csv.md
+++ b/tests/testthat/_snaps/csv.md
@@ -429,3 +429,21 @@
       2023-10-16T22:45:00.000000
       2023-10-16T23:00:00.000000
 
+# write_csv: float_precision works
+
+    Code
+      cat(readLines(path), sep = "\n")
+    Output
+      x
+      1.2
+      5.6
+
+---
+
+    Code
+      cat(readLines(path), sep = "\n")
+    Output
+      x
+      1.234
+      5.600
+
diff --git a/tests/testthat/test-csv.R b/tests/testthat/test-csv.R
index 3dd9e1b66..a07bbb863 100644
--- a/tests/testthat/test-csv.R
+++ b/tests/testthat/test-csv.R
@@ -121,3 +121,13 @@ test_that("write_csv: time_format works", {
   dat$write_csv(temp_out, time_format = "%Hh%Mm%%Ss")
   expect_snapshot_file(temp_out)
 })
+
+
+test_that("write_csv: float_precision works", {
+  dat <- pl$DataFrame(x = c(1.234, 5.6))
+  dat$write_csv(temp_out, float_precision = 1)
+  expect_snapshot_file(temp_out)
+
+  dat$write_csv(temp_out, float_precision = 3)
+  expect_snapshot_file(temp_out)
+})

From 32294710390087877f33f5ee76f02e8111d56c65 Mon Sep 17 00:00:00 2001
From: Etienne Bacher <52219252+etiennebacher@users.noreply.github.com>
Date: Tue, 17 Oct 2023 13:36:04 +0200
Subject: [PATCH 17/25] add examples

---
 R/dataframe__frame.R | 4 ++++
 man/IO_write_csv.Rd  | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/R/dataframe__frame.R b/R/dataframe__frame.R
index e82baae9b..c1bde697f 100644
--- a/R/dataframe__frame.R
+++ b/R/dataframe__frame.R
@@ -1726,6 +1726,10 @@ DataFrame_sample = function(
 #' @examples
 #' dat = pl$DataFrame(mtcars)
 #'
+#' destination = tempfile(fileext = ".csv")
+#' dat$select(pl$col("drat", "mpg"))$write_csv(destination)
+#'
+#' pl$read_csv(destination)
 
 DataFrame_write_csv = function(
     path,
diff --git a/man/IO_write_csv.Rd b/man/IO_write_csv.Rd
index 0d2cca41d..bf9ed3fc6 100644
--- a/man/IO_write_csv.Rd
+++ b/man/IO_write_csv.Rd
@@ -71,4 +71,8 @@ Write to comma-separated values (CSV) file
 \examples{
 dat = pl$DataFrame(mtcars)
 
+destination = tempfile(fileext = ".csv")
+dat$select(pl$col("drat", "mpg"))$write_csv(destination)
+
+pl$read_csv(destination)
 }

From 3539a04532ab5ec3089d4c96b63437f068e94cde Mon Sep 17 00:00:00 2001
From: Etienne Bacher <52219252+etiennebacher@users.noreply.github.com>
Date: Tue, 17 Oct 2023 14:08:08 +0200
Subject: [PATCH 18/25] remove time_format test for now

---
 tests/testthat/_snaps/csv.md | 12 ------------
 tests/testthat/test-csv.R    | 25 +++++++++++++------------
 2 files changed, 13 insertions(+), 24 deletions(-)

diff --git a/tests/testthat/_snaps/csv.md b/tests/testthat/_snaps/csv.md
index fbfd5d01c..aecb27a65 100644
--- a/tests/testthat/_snaps/csv.md
+++ b/tests/testthat/_snaps/csv.md
@@ -417,18 +417,6 @@
       18h00m - 01/01/2020
       00h00m - 02/01/2020
 
-# write_csv: time_format works
-
-    Code
-      cat(readLines(path), sep = "\n")
-    Output
-      date
-      2023-10-16T22:00:00.000000
-      2023-10-16T22:15:00.000000
-      2023-10-16T22:30:00.000000
-      2023-10-16T22:45:00.000000
-      2023-10-16T23:00:00.000000
-
 # write_csv: float_precision works
 
     Code
diff --git a/tests/testthat/test-csv.R b/tests/testthat/test-csv.R
index a07bbb863..a37400c29 100644
--- a/tests/testthat/test-csv.R
+++ b/tests/testthat/test-csv.R
@@ -109,18 +109,19 @@ test_that("write_csv: datetime_format works", {
   expect_snapshot_file(temp_out)
 })
 
-test_that("write_csv: time_format works", {
-  dat <- pl$DataFrame(
-    date = pl$date_range(
-      strptime("00:00:00", format = "%H:%M:%S"),
-      strptime("01:00:00", format = "%H:%M:%S"),
-      interval = "15m",
-      eager = TRUE
-    )
-  )
-  dat$write_csv(temp_out, time_format = "%Hh%Mm%%Ss")
-  expect_snapshot_file(temp_out)
-})
+# TODO: uncomment this when $dt$time is implemented
+# test_that("write_csv: time_format works", {
+#   dat <- pl$DataFrame(
+#     date = pl$date_range(
+#       strptime("00:00:00", format = "%H:%M:%S"),
+#       strptime("01:00:00", format = "%H:%M:%S"),
+#       interval = "15m",
+#       eager = TRUE
+#     )$dt$time()
+#   )
+#   dat$write_csv(temp_out, time_format = "%Hh%Mm%%Ss")
+#   expect_snapshot_file(temp_out)
+# })
 
 
 test_that("write_csv: float_precision works", {

From 53cfc9c32b6bd9de3f4516401912f39ae00a778a Mon Sep 17 00:00:00 2001
From: sorhawell <sorhawell@gmail.com>
Date: Wed, 18 Oct 2023 00:34:21 +0200
Subject: [PATCH 19/25] more robj_to!(x,y)?, add QuoteStyle, Utf8Byte

---
 R/dataframe__frame.R           |  8 +----
 src/rust/src/rdataframe/mod.rs | 56 +++++++++++-----------------------
 src/rust/src/utils/mod.rs      | 31 +++++++++++++++++++
 3 files changed, 49 insertions(+), 46 deletions(-)

diff --git a/R/dataframe__frame.R b/R/dataframe__frame.R
index c1bde697f..83bcf0055 100644
--- a/R/dataframe__frame.R
+++ b/R/dataframe__frame.R
@@ -1730,7 +1730,6 @@ DataFrame_sample = function(
 #' dat$select(pl$col("drat", "mpg"))$write_csv(destination)
 #'
 #' pl$read_csv(destination)
-
 DataFrame_write_csv = function(
     path,
     has_header = TRUE,
@@ -1746,14 +1745,9 @@ DataFrame_write_csv = function(
     quote_style = "necessary"
 ) {
 
-  if (length(quote_style) == 0 ||
-      !quote_style %in% c("always", "necessary", "non_numeric")) {
-    stop("Argument `quote_style` must be one of 'always', 'necessary', or 'non_numeric'.")
-  }
-
   .pr$DataFrame$write_csv(
     self,
-    path, has_header, utf8ToInt(separator), line_terminator, utf8ToInt(quote), batch_size,
+    path, has_header, separator, line_terminator, quote, batch_size,
     datetime_format, date_format, time_format, float_precision,
     null_values, quote_style
   ) |>
diff --git a/src/rust/src/rdataframe/mod.rs b/src/rust/src/rdataframe/mod.rs
index 232af2078..5d96d7ffe 100644
--- a/src/rust/src/rdataframe/mod.rs
+++ b/src/rust/src/rdataframe/mod.rs
@@ -1,5 +1,5 @@
 use extendr_api::{extendr, prelude::*, rprintln, Rinternals};
-use polars::prelude::{self as pl, IntoLazy};
+use polars::prelude::{self as pl, IntoLazy, SerWriter};
 use std::result::Result;
 pub mod read_csv;
 pub mod read_ipc;
@@ -11,8 +11,6 @@ use crate::rdatatype::RPolarsDataType;
 use crate::robj_to;
 use crate::rpolarserr::*;
 
-use polars::prelude::{CsvWriter, QuoteStyle, SerWriter};
-
 pub use lazy::dataframe::*;
 
 use crate::conversion_s_to_r::pl_series_to_list;
@@ -446,7 +444,7 @@ impl DataFrame {
     }
 
     pub fn write_csv(
-        &mut self,
+        &self,
         path: Robj,
         has_header: Robj,
         separator: Robj,
@@ -460,45 +458,25 @@ impl DataFrame {
         null_value: Robj,
         quote_style: Robj,
     ) -> RResult<()> {
-        let null = robj_to!(String, null_value).unwrap();
-        let path = robj_to!(str, path).unwrap();
-        let f = std::fs::File::create(path).unwrap();
-        let qs = parse_quote_style(quote_style);
-
-        CsvWriter::new(f)
-            .has_header(robj_to!(bool, has_header).unwrap())
-            .with_delimiter(robj_to!(u8, separator).unwrap())
-            .with_line_terminator(robj_to!(String, line_terminator).unwrap())
-            .with_quoting_char(robj_to!(u8, quote).unwrap())
-            .with_batch_size(robj_to!(usize, batch_size).unwrap())
-            .with_datetime_format(robj_to!(Option, String, datetime_format).unwrap())
-            .with_date_format(robj_to!(Option, String, date_format).unwrap())
-            .with_time_format(robj_to!(Option, String, time_format).unwrap())
-            .with_float_precision(robj_to!(Option, usize, float_precision).unwrap())
-            .with_null_value(null)
-            .with_quote_style(qs)
-            .finish(&mut self.0)
+        let path = robj_to!(str, path)?;
+        let f = std::fs::File::create(path)?;
+        pl::CsvWriter::new(f)
+            .has_header(robj_to!(bool, has_header)?)
+            .with_delimiter(robj_to!(Utf8Byte, separator)?)
+            .with_line_terminator(robj_to!(String, line_terminator)?)
+            .with_quoting_char(robj_to!(Utf8Byte, quote)?)
+            .with_batch_size(robj_to!(usize, batch_size)?)
+            .with_datetime_format(robj_to!(Option, String, datetime_format)?)
+            .with_date_format(robj_to!(Option, String, date_format)?)
+            .with_time_format(robj_to!(Option, String, time_format)?)
+            .with_float_precision(robj_to!(Option, usize, float_precision)?)
+            .with_null_value(robj_to!(String, null_value)?)
+            .with_quote_style(robj_to!(QuoteStyle, quote_style)?)
+            .finish(&mut self.0.clone())
             .map_err(polars_to_rpolars_err)
     }
 }
 
-pub fn parse_quote_style(x: Robj) -> QuoteStyle {
-    match robj_to!(Option, String, x)
-        .unwrap_or_default()
-        .unwrap()
-        .as_str()
-    {
-        "always" => QuoteStyle::Always,
-        "necessary" => QuoteStyle::Necessary,
-        "non_numeric" => QuoteStyle::NonNumeric,
-        // "never" is available in rust-polars devel only for now (will be added in 0.34)
-        // "never" => QuoteStyle::Never,
-        _ => panic!(
-            "polars internal error: `quote_style` must be 'always', 'necessary' or 'non_numeric'."
-        ),
-    }
-}
-
 impl DataFrame {
     pub fn to_list_result(&self) -> Result<Robj, pl::PolarsError> {
         //convert DataFrame to Result of to R vectors, error if DataType is not supported
diff --git a/src/rust/src/utils/mod.rs b/src/rust/src/utils/mod.rs
index aa28bb6eb..d11715755 100644
--- a/src/rust/src/utils/mod.rs
+++ b/src/rust/src/utils/mod.rs
@@ -535,6 +535,29 @@ pub fn robj_to_usize(robj: extendr_api::Robj) -> RResult<usize> {
     robj_to_u64(robj).and_then(try_u64_into_usize)
 }
 
+pub fn robj_to_utf8_byte(robj: extendr_api::Robj) -> RResult<u8> {
+    let mut utf8_byte_iter = robj_to_str(robj)?.as_bytes().iter();
+    match (utf8_byte_iter.next(), utf8_byte_iter.next()) {
+        (Some(s), None) => Ok(*s),
+        (None, None) => rerr().plain("cannot extract single byte from empty string"),
+        (Some(_), Some(_)) => rerr().plain("multi byte-string not allowed"),
+        (None, Some(_)) => unreachable!("the iter() cannot yield Some after None(depleted)"),
+    }
+}
+
+pub fn robj_to_quote_style(robj: Robj) -> RResult<pl::QuoteStyle> {
+    match robj_to_str(robj.clone())? {
+        "always" => Ok(pl::QuoteStyle::Always),
+        "necessary" => Ok(pl::QuoteStyle::Necessary),
+        "non_numeric" => Ok(pl::QuoteStyle::NonNumeric),
+        // "never" is available in rust-polars devel only for now (will be added in 0.34)
+        // "never" => Ok(QuoteStyle::Never),
+        _ => rerr()
+            .plain("a `quote_style` must be 'always', 'necessary' or 'non_numeric'.")
+            .bad_robj(&robj),
+    }
+}
+
 fn err_no_nan<T>() -> RResult<T> {
     rerr().plain("any NA value is not allowed here".to_string())
 }
@@ -885,6 +908,10 @@ macro_rules! robj_to_inner {
         $crate::utils::robj_to_u8($a)
     };
 
+    (Utf8Byte, $a:ident) => {
+        $crate::utils::robj_to_utf8_byte($a)
+    };
+
     (char, $a:ident) => {
         $crate::utils::robj_to_char($a)
     };
@@ -985,6 +1012,10 @@ macro_rules! robj_to_inner {
         $crate::utils::robj_to_dataframe($a).map(|lf| lf.0)
     };
 
+    (QuoteStyle, $a:ident) => {
+        $crate::utils::robj_to_quote_style($a)
+    };
+
     (RArrow_schema, $a:ident) => {
         $crate::utils::robj_to_rarrow_schema($a)
     };

From d8949bb1885040fbc637a9f25b2437311053dc42 Mon Sep 17 00:00:00 2001
From: sorhawell <sorhawell@gmail.com>
Date: Wed, 18 Oct 2023 00:56:44 +0200
Subject: [PATCH 20/25] unit test new robj_to! conversions and errors

---
 tests/testthat/test-csv.R | 29 ++++++++++++++++++++++++-----
 1 file changed, 24 insertions(+), 5 deletions(-)

diff --git a/tests/testthat/test-csv.R b/tests/testthat/test-csv.R
index a37400c29..58fde3152 100644
--- a/tests/testthat/test-csv.R
+++ b/tests/testthat/test-csv.R
@@ -56,16 +56,35 @@ test_that("write_csv: separator works", {
 test_that("write_csv: quote_style and quote works", {
   dat_pl2 = pl$DataFrame(iris)
 
-  expect_error(
-    dat_pl2$write_csv(temp_out, quote_style = "foo"),
-    "must be one of"
-  )
+  #wrong quote_style
+  ctx = dat_pl2$write_csv(temp_out, quote_style = "foo") |> get_err_ctx()
+  expect_identical(ctx$BadArgument, "quote_style")
+  expect_identical(ctx$Plain, "a `quote_style` must be 'always', 'necessary' or 'non_numeric'.")
 
+  # wrong quote_style type
+  ctx = dat_pl2$write_csv(temp_out, quote_style = 42) |> get_err_ctx()
+  expect_identical(ctx$TypeMismatch, "&str")
+
+  # ok quote_style and quote
   dat_pl2$write_csv(temp_out, quote_style = "always", quote = "+")
   expect_snapshot_file(temp_out)
 
-  dat_pl2$write_csv(temp_out, quote_style = "non_numeric", quote = "+")
+  # ok also
+  ctx = dat_pl2$write_csv(temp_out, quote_style = "non_numeric", quote = "+")
   expect_snapshot_file(temp_out)
+
+  # zero byte quote
+  ctx = dat_pl2$write_csv(temp_out, quote = "") |> get_err_ctx()
+  expect_identical(ctx$Plain, "cannot extract single byte from empty string")
+
+  # multi byte quote not allowed
+  ctx = dat_pl2$write_csv(temp_out, quote = "£") |> get_err_ctx()
+  expect_identical(ctx$Plain, "multi byte-string not allowed")
+
+  # multi string not allowed
+  ctx = dat_pl2$write_csv(temp_out, quote = c("a","b")) |> get_err_ctx()
+  expect_identical(ctx$TypeMismatch, "&str")
+
 })
 
 patrick::with_parameters_test_that(

From 1e5bcba857195522d6482a6469617c301b42da57 Mon Sep 17 00:00:00 2001
From: Etienne Bacher <52219252+etiennebacher@users.noreply.github.com>
Date: Wed, 18 Oct 2023 08:32:42 +0200
Subject: [PATCH 21/25] do not export

---
 NAMESPACE            | 1 -
 R/dataframe__frame.R | 2 +-
 2 files changed, 1 insertion(+), 2 deletions(-)

diff --git a/NAMESPACE b/NAMESPACE
index b7e654aa8..14166760d 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -153,7 +153,6 @@ S3method(tail,LazyFrame)
 S3method(unique,DataFrame)
 S3method(unique,LazyFrame)
 export(.pr)
-export(DataFrame_write_csv)
 export(as_polars_series)
 export(knit_print.DataFrame)
 export(pl)
diff --git a/R/dataframe__frame.R b/R/dataframe__frame.R
index 83bcf0055..fe1929f0e 100644
--- a/R/dataframe__frame.R
+++ b/R/dataframe__frame.R
@@ -1720,7 +1720,7 @@ DataFrame_sample = function(
 
 #' @return
 #' This doesn't return anything but creates a CSV file.
-#' @export
+#'
 #' @rdname IO_write_csv
 #'
 #' @examples

From 5e5473acffca8c13462df811aa466216bc756e4d Mon Sep 17 00:00:00 2001
From: Etienne Bacher <52219252+etiennebacher@users.noreply.github.com>
Date: Wed, 18 Oct 2023 08:35:35 +0200
Subject: [PATCH 22/25] remove unused utils

---
 R/utils.R | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/R/utils.R b/R/utils.R
index 0cf103154..46b3c1dd1 100644
--- a/R/utils.R
+++ b/R/utils.R
@@ -620,9 +620,3 @@ is_bool = function(x) {
 dtypes_are_struct = function(dtypes) {
   sapply(dtypes, \(dt) pl$same_outer_dt(dt, pl$Struct()))
 }
-
-# from tools::file_ext()
-file_ext <- function(x) {
-  pos <- regexpr("\\.([[:alnum:]]+)$", x)
-  ifelse(pos > -1L, substring(x, pos + 1L), "")
-}

From 55a83580b2a43716ecf6d945e36bf6f0694615d1 Mon Sep 17 00:00:00 2001
From: Etienne Bacher <52219252+etiennebacher@users.noreply.github.com>
Date: Wed, 18 Oct 2023 08:38:33 +0200
Subject: [PATCH 23/25] uncomment a test

---
 tests/testthat/_snaps/csv.md | 12 ++++++++++++
 tests/testthat/test-csv.R    | 25 ++++++++++++-------------
 2 files changed, 24 insertions(+), 13 deletions(-)

diff --git a/tests/testthat/_snaps/csv.md b/tests/testthat/_snaps/csv.md
index aecb27a65..6bf215bb7 100644
--- a/tests/testthat/_snaps/csv.md
+++ b/tests/testthat/_snaps/csv.md
@@ -417,6 +417,18 @@
       18h00m - 01/01/2020
       00h00m - 02/01/2020
 
+# write_csv: time_format works
+
+    Code
+      cat(readLines(path), sep = "\n")
+    Output
+      date
+      22h00m00s
+      22h15m00s
+      22h30m00s
+      22h45m00s
+      23h00m00s
+
 # write_csv: float_precision works
 
     Code
diff --git a/tests/testthat/test-csv.R b/tests/testthat/test-csv.R
index 58fde3152..5b3fab7c2 100644
--- a/tests/testthat/test-csv.R
+++ b/tests/testthat/test-csv.R
@@ -128,19 +128,18 @@ test_that("write_csv: datetime_format works", {
   expect_snapshot_file(temp_out)
 })
 
-# TODO: uncomment this when $dt$time is implemented
-# test_that("write_csv: time_format works", {
-#   dat <- pl$DataFrame(
-#     date = pl$date_range(
-#       strptime("00:00:00", format = "%H:%M:%S"),
-#       strptime("01:00:00", format = "%H:%M:%S"),
-#       interval = "15m",
-#       eager = TRUE
-#     )$dt$time()
-#   )
-#   dat$write_csv(temp_out, time_format = "%Hh%Mm%%Ss")
-#   expect_snapshot_file(temp_out)
-# })
+test_that("write_csv: time_format works", {
+  dat <- pl$DataFrame(
+    date = pl$date_range(
+      strptime("00:00:00", format = "%H:%M:%S"),
+      strptime("01:00:00", format = "%H:%M:%S"),
+      interval = "15m",
+      eager = TRUE
+    )
+  )$with_columns(pl$col("date")$dt$time())
+  dat$write_csv(temp_out, time_format = "%Hh%Mm%Ss")
+  expect_snapshot_file(temp_out)
+})
 
 
 test_that("write_csv: float_precision works", {

From d53f912b954ca8597f6e93f9670cabf411da39a8 Mon Sep 17 00:00:00 2001
From: Etienne Bacher <52219252+etiennebacher@users.noreply.github.com>
Date: Wed, 18 Oct 2023 13:39:13 +0200
Subject: [PATCH 24/25] try to fix test

---
 tests/testthat/_snaps/csv.md | 9 ++++-----
 tests/testthat/test-csv.R    | 6 +++---
 2 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/tests/testthat/_snaps/csv.md b/tests/testthat/_snaps/csv.md
index 6bf215bb7..84c909389 100644
--- a/tests/testthat/_snaps/csv.md
+++ b/tests/testthat/_snaps/csv.md
@@ -423,11 +423,10 @@
       cat(readLines(path), sep = "\n")
     Output
       date
-      22h00m00s
-      22h15m00s
-      22h30m00s
-      22h45m00s
-      23h00m00s
+      00h00m00s
+      08h00m00s
+      16h00m00s
+      00h00m00s
 
 # write_csv: float_precision works
 
diff --git a/tests/testthat/test-csv.R b/tests/testthat/test-csv.R
index 5b3fab7c2..3a6acb375 100644
--- a/tests/testthat/test-csv.R
+++ b/tests/testthat/test-csv.R
@@ -131,9 +131,9 @@ test_that("write_csv: datetime_format works", {
 test_that("write_csv: time_format works", {
   dat <- pl$DataFrame(
     date = pl$date_range(
-      strptime("00:00:00", format = "%H:%M:%S"),
-      strptime("01:00:00", format = "%H:%M:%S"),
-      interval = "15m",
+      as.Date("2020-10-17"),
+      as.Date("2020-10-18"),
+      "8h",
       eager = TRUE
     )
   )$with_columns(pl$col("date")$dt$time())

From 2e2a4a817f6be8b57a92ead17ba70ada454e8f60 Mon Sep 17 00:00:00 2001
From: eitsupi <ts1s1andn@gmail.com>
Date: Wed, 18 Oct 2023 12:14:58 +0000
Subject: [PATCH 25/25] refactor: auto formatting

---
 R/dataframe__frame.R      |  4 +---
 src/rust/src/lazy/dsl.rs  |  7 +------
 tests/testthat/test-csv.R | 13 ++++++-------
 3 files changed, 8 insertions(+), 16 deletions(-)

diff --git a/R/dataframe__frame.R b/R/dataframe__frame.R
index fe1929f0e..fa3636336 100644
--- a/R/dataframe__frame.R
+++ b/R/dataframe__frame.R
@@ -1742,9 +1742,7 @@ DataFrame_write_csv = function(
     time_format = NULL,
     float_precision = NULL,
     null_values = "",
-    quote_style = "necessary"
-) {
-
+    quote_style = "necessary") {
   .pr$DataFrame$write_csv(
     self,
     path, has_header, separator, line_terminator, quote, batch_size,
diff --git a/src/rust/src/lazy/dsl.rs b/src/rust/src/lazy/dsl.rs
index 26cd804c0..683e73322 100644
--- a/src/rust/src/lazy/dsl.rs
+++ b/src/rust/src/lazy/dsl.rs
@@ -1314,12 +1314,7 @@ impl Expr {
     }
 
     pub fn dt_time(&self) -> RResult<Self> {
-        Ok(self
-            .0
-            .clone()
-            .dt()
-            .time()
-            .into())
+        Ok(self.0.clone().dt().time().into())
     }
 
     pub fn dt_combine(&self, time: Robj, tu: Robj) -> RResult<Expr> {
diff --git a/tests/testthat/test-csv.R b/tests/testthat/test-csv.R
index 3a6acb375..0933e5379 100644
--- a/tests/testthat/test-csv.R
+++ b/tests/testthat/test-csv.R
@@ -56,7 +56,7 @@ test_that("write_csv: separator works", {
 test_that("write_csv: quote_style and quote works", {
   dat_pl2 = pl$DataFrame(iris)
 
-  #wrong quote_style
+  # wrong quote_style
   ctx = dat_pl2$write_csv(temp_out, quote_style = "foo") |> get_err_ctx()
   expect_identical(ctx$BadArgument, "quote_style")
   expect_identical(ctx$Plain, "a `quote_style` must be 'always', 'necessary' or 'non_numeric'.")
@@ -82,9 +82,8 @@ test_that("write_csv: quote_style and quote works", {
   expect_identical(ctx$Plain, "multi byte-string not allowed")
 
   # multi string not allowed
-  ctx = dat_pl2$write_csv(temp_out, quote = c("a","b")) |> get_err_ctx()
+  ctx = dat_pl2$write_csv(temp_out, quote = c("a", "b")) |> get_err_ctx()
   expect_identical(ctx$TypeMismatch, "&str")
-
 })
 
 patrick::with_parameters_test_that(
@@ -101,7 +100,7 @@ patrick::with_parameters_test_that(
 )
 
 test_that("write_csv: date_format works", {
-  dat <- pl$DataFrame(
+  dat = pl$DataFrame(
     date = pl$date_range(
       as.Date("2020-01-01"),
       as.Date("2023-01-02"),
@@ -116,7 +115,7 @@ test_that("write_csv: date_format works", {
 })
 
 test_that("write_csv: datetime_format works", {
-  dat <- pl$DataFrame(
+  dat = pl$DataFrame(
     date = pl$date_range(
       as.Date("2020-01-01"),
       as.Date("2020-01-02"),
@@ -129,7 +128,7 @@ test_that("write_csv: datetime_format works", {
 })
 
 test_that("write_csv: time_format works", {
-  dat <- pl$DataFrame(
+  dat = pl$DataFrame(
     date = pl$date_range(
       as.Date("2020-10-17"),
       as.Date("2020-10-18"),
@@ -143,7 +142,7 @@ test_that("write_csv: time_format works", {
 
 
 test_that("write_csv: float_precision works", {
-  dat <- pl$DataFrame(x = c(1.234, 5.6))
+  dat = pl$DataFrame(x = c(1.234, 5.6))
   dat$write_csv(temp_out, float_precision = 1)
   expect_snapshot_file(temp_out)