refactor: some cleanup and more tests for $rolling() (#1103)

R/dataframe__frame.R

@@ -2131,9 +2131,8 @@ DataFrame_rolling = function(
     closed = "right",
     group_by = NULL,
     check_sorted = TRUE) {
-  if (is.null(offset)) {
-    offset = paste0("-", period) # TODO: `paste0` should be executed after `period` is parsed as string
-  }
+  period = parse_as_polars_duration_string(period)
+  offset = parse_as_polars_duration_string(offset) %||% negate_duration_string(period)
   construct_rolling_group_by(self, index_column, period, offset, closed, group_by, check_sorted)
 }
 
@@ -2217,7 +2216,7 @@ DataFrame_group_by_dynamic = function(
     start_by = "window",
     check_sorted = TRUE) {
   every = parse_as_polars_duration_string(every)
-  offset = parse_as_polars_duration_string(offset) %||% paste0("-", every)
+  offset = parse_as_polars_duration_string(offset) %||% negate_duration_string(every)
   period = parse_as_polars_duration_string(period) %||% every
   construct_group_by_dynamic(
     self, index_column, every, period, offset, include_boundaries, closed, label,

R/expr__expr.R

@@ -3316,11 +3316,12 @@ Expr_peak_max = function() {
 Expr_rolling = function(
     index_column,
     ...,
-    period, offset = NULL,
-    closed = "right", check_sorted = TRUE) {
-  if (is.null(offset)) {
-    offset = paste0("-", period) # TODO: `paste0` should be executed after `period` is parsed as string
-  }
+    period,
+    offset = NULL,
+    closed = "right",
+    check_sorted = TRUE) {
+  period = parse_as_polars_duration_string(period)
+  offset = parse_as_polars_duration_string(offset) %||% negate_duration_string(period)
   .pr$Expr$rolling(self, index_column, period, offset, closed, check_sorted) |>
     unwrap("in $rolling():")
 }

R/lazyframe__lazy.R

@@ -1914,9 +1914,8 @@ LazyFrame_rolling = function(
     closed = "right",
     group_by = NULL,
     check_sorted = TRUE) {
-  if (is.null(offset)) {
-    offset = paste0("-", period) # TODO: `paste0` should be executed after `period` is parsed as string
-  }
+  period = parse_as_polars_duration_string(period)
+  offset = parse_as_polars_duration_string(offset) %||% negate_duration_string(period)
   .pr$LazyFrame$rolling(
     self, index_column, period, offset, closed,
     wrap_elist_result(group_by, str_to_lit = FALSE), check_sorted
@@ -2026,7 +2025,7 @@ LazyFrame_group_by_dynamic = function(
     start_by = "window",
     check_sorted = TRUE) {
   every = parse_as_polars_duration_string(every)
-  offset = parse_as_polars_duration_string(offset) %||% paste0("-", every)
+  offset = parse_as_polars_duration_string(offset) %||% negate_duration_string(every)
   period = parse_as_polars_duration_string(period) %||% every
 
   .pr$LazyFrame$group_by_dynamic(

R/parse_as_duration.R

@@ -56,21 +56,19 @@ parse_as_polars_duration_string.default = function(x, default = NULL, ...) {
     unwrap()
 }
 
-
 #' @exportS3Method
 parse_as_polars_duration_string.character = function(x, default = NULL, ...) {
-  if (length(x) != 1L || is.na(x)) {
+  if (length(x) != 1L) {
     Err_plain(paste0("`", deparse(substitute(x)), "` must be a single non-NA character or difftime.")) |>
       unwrap()
   }
 
   x
 }
 
-
 #' @exportS3Method
 parse_as_polars_duration_string.difftime = function(x, default = NULL, ...) {
-  if (length(x) != 1L || is.na(x)) {
+  if (length(x) != 1L) {
     Err_plain(paste0("`", deparse(substitute(x)), "` must be a single non-NA character or difftime.")) |>
       unwrap()
   }
@@ -95,3 +93,11 @@ difftime_to_duration_string = function(dft) {
   )
   paste0(value, unit)
 }
+
+negate_duration_string = function(x) {
+  if (startsWith(x, "-")) {
+    gsub("^-", "", x)
+  } else {
+    paste0("-", x)
+  }
+}

tests/testthat/test-dataframe.R

@@ -1323,6 +1323,38 @@ test_that("rolling for DataFrame: basic example", {
   )
 })
 
+test_that("rolling for DataFrame: using difftime as period", {
+  df = pl$DataFrame(
+    dt = c(
+      "2020-01-01", "2020-01-01", "2020-01-01",
+      "2020-01-02", "2020-01-03", "2020-01-08"
+    ),
+    a = c(3, 7, 5, 9, 2, 1)
+  )$with_columns(
+    pl$col("dt")$str$strptime(pl$Date, format = NULL)$set_sorted()
+  )
+
+  expect_equal(
+    df$rolling(index_column = "dt", period = "2d")$agg(
+      pl$sum("a")$alias("sum_a")
+    )$to_data_frame(),
+    df$rolling(index_column = "dt", period = as.difftime(2, units = "days"))$agg(
+      pl$sum("a")$alias("sum_a")
+    )$to_data_frame()
+  )
+})
+
+test_that("rolling for LazyFrame: error if period is negative", {
+  df = pl$LazyFrame(
+    index = c(1L, 2L, 3L, 4L, 8L, 9L),
+    a = c(3, 7, 5, 9, 2, 1)
+  )
+  expect_grepl_error(
+    df$rolling(index_column = "index", period = "-2i")$agg(pl$col("a"))$collect(),
+    "rolling window period should be strictly positive"
+  )
+})
+
 test_that("rolling for DataFrame: can be ungrouped", {
   df = pl$DataFrame(
     index = c(1:5, 6.0),

tests/testthat/test-expr_expr.R

@@ -2577,6 +2577,42 @@ test_that("rolling, arg offset", {
   )
 })
 
+test_that("rolling: error if period is negative", {
+  dates = c(
+    "2020-01-01 13:45:48", "2020-01-01 16:42:13", "2020-01-01 16:45:09",
+    "2020-01-02 18:12:48", "2020-01-03 19:45:32", "2020-01-08 23:16:43"
+  )
+
+  df = pl$DataFrame(dt = dates, a = c(3, 7, 5, 9, 2, 1))$
+    with_columns(
+      pl$col("dt")$str$strptime(pl$Datetime("us"), format = "%Y-%m-%d %H:%M:%S")$set_sorted()
+    )
+  expect_grepl_error(
+    df$select(pl$col("a")$rolling(index_column = "dt", period = "-2d")),
+    "rolling window period should be strictly positive"
+  )
+})
+
+test_that("rolling: passing a difftime as period works", {
+  dates = c(
+    "2020-01-01 13:45:48", "2020-01-01 16:42:13", "2020-01-01 16:45:09",
+    "2020-01-02 18:12:48", "2020-01-03 19:45:32", "2020-01-08 23:16:43"
+  )
+
+  df = pl$DataFrame(dt = dates, a = c(3, 7, 5, 9, 2, 1))$
+    with_columns(
+      pl$col("dt")$str$strptime(pl$Datetime("us"), format = "%Y-%m-%d %H:%M:%S")$set_sorted()
+    )
+  expect_identical(
+    df$select(
+      sum_a_offset1 = pl$sum("a")$rolling(index_column = "dt", period = "2d", offset = "1d")
+    )$to_data_frame(),
+    df$select(
+      sum_a_offset1 = pl$sum("a")$rolling(index_column = "dt", period = as.difftime(2, units = "days"), offset = "1d")
+    )$to_data_frame()
+  )
+})
+
 test_that("rolling, arg check_sorted", {
   dates = c(
     "2020-01-02 18:12:48", "2020-01-03 19:45:32", "2020-01-08 23:16:43",

tests/testthat/test-groupby.R

@@ -274,6 +274,18 @@ test_that("group_by_dynamic for LazyFrame: error if not explicitly sorted", {
   )
 })
 
+test_that("group_by_dynamic for LazyFrame: error if every is negative", {
+  df = pl$LazyFrame(
+    idx = 0:5,
+    n = 0:5
+  )$with_columns(pl$col("idx")$set_sorted())
+
+  expect_grepl_error(
+    df$group_by_dynamic("idx", every = "-2i")$agg(pl$col("n")$mean())$collect(),
+    "'every' argument must be positive"
+  )
+})
+
 test_that("group_by_dynamic for LazyFrame: arg 'closed' works", {
   df = pl$LazyFrame(
     dt = c(

tests/testthat/test-lazy.R

@@ -951,6 +951,27 @@ test_that("rolling for LazyFrame: integer variable", {
   )
 })
 
+test_that("rolling for LazyFrame: using difftime as period", {
+  df = pl$LazyFrame(
+    dt = c(
+      "2020-01-01", "2020-01-01", "2020-01-01",
+      "2020-01-02", "2020-01-03", "2020-01-08"
+    ),
+    a = c(3, 7, 5, 9, 2, 1)
+  )$with_columns(
+    pl$col("dt")$str$strptime(pl$Date, format = NULL)$set_sorted()
+  )
+
+  expect_equal(
+    df$rolling(index_column = "dt", period = "2d")$agg(
+      pl$sum("a")$alias("sum_a")
+    )$collect()$to_data_frame(),
+    df$rolling(index_column = "dt", period = as.difftime(2, units = "days"))$agg(
+      pl$sum("a")$alias("sum_a")
+    )$collect()$to_data_frame()
+  )
+})
+
 test_that("rolling for LazyFrame: error if not explicitly sorted", {
   df = pl$LazyFrame(
     index = c(1L, 2L, 3L, 4L, 8L, 9L),
@@ -962,6 +983,17 @@ test_that("rolling for LazyFrame: error if not explicitly sorted", {
   )
 })
 
+test_that("rolling for LazyFrame: error if period is negative", {
+  df = pl$LazyFrame(
+    index = c(1L, 2L, 3L, 4L, 8L, 9L),
+    a = c(3, 7, 5, 9, 2, 1)
+  )
+  expect_grepl_error(
+    df$rolling(index_column = "index", period = "-2i")$agg(pl$col("a"))$collect(),
+    "rolling window period should be strictly positive"
+  )
+})
+
 test_that("rolling for LazyFrame: argument 'group_by' works", {
   df = pl$LazyFrame(
     index = c(1L, 2L, 3L, 4L, 8L, 9L),