Merge branch 'main' into vignette-diff-python

NAMESPACE

@@ -176,8 +176,10 @@ S3method(as_polars_series,clock_time_point)
 S3method(as_polars_series,clock_zoned_time)
 S3method(as_polars_series,data.frame)
 S3method(as_polars_series,default)
+S3method(as_polars_series,list)
 S3method(as_polars_series,nanoarrow_array)
 S3method(as_polars_series,nanoarrow_array_stream)
+S3method(as_polars_series,rpolars_raw_list)
 S3method(as_polars_series,vctrs_rcrd)
 S3method(c,RPolarsSeries)
 S3method(dim,RPolarsDataFrame)

NEWS.md

@@ -13,6 +13,36 @@
 
 ### Other breaking changes
 
+- R objects inside an R list are now converted to Polars data types via
+  `as_polars_series()` (#1021). For example, up to polars 0.15.1,
+  data.frames inside a list were converted to a nested List type:
+
+  ```r
+  pl$select(nested_data = pl$lit(list(data.frame(a = 1))))
+  #> shape: (1, 1)
+  #> ┌─────────────────┐
+  #> │ nested_data     │
+  #> │ ---             │
+  #> │ list[list[f64]] │
+  #> ╞═════════════════╡
+  #> │ [[1.0]]         │
+  #> └─────────────────┘
+  ```
+
+  From 0.16.0, data.frames inside a list are converted to the polars Struct type:
+
+  ```r
+  pl$select(nested_data = pl$lit(list(data.frame(a = 1))))
+  #> shape: (1, 1)
+  #> ┌─────────────────┐
+  #> │ nested_data     │
+  #> │ ---             │
+  #> │ list[struct[1]] │
+  #> ╞═════════════════╡
+  #> │ [{1.0}]         │
+  #> └─────────────────┘
+  ```
+
 - Several functions have been rewritten to match the behavior of Python Polars.
 
   - In `pl$Series()` arguments are changed.

R/as_polars.R

@@ -523,3 +523,25 @@ as_polars_series.clock_zoned_time = function(x, name = NULL, ...) {
     ...
   )$dt$replace_time_zone(time_zone)
 }
+
+
+# TODO: rewrite `recursive_robjname2series_tree` in Rust side
+#' @rdname as_polars_series
+#' @export
+as_polars_series.list = function(x, name = NULL, ...) {
+  lapply(x, \(child) {
+    if (is.null(child)) {
+      NULL # if `NULL`, the type will be resolved later
+    } else {
+      as_polars_series(child)
+    }
+  }) |>
+    as_polars_series.default(name = name)
+}
+
+
+# TODO: reconsider `rpolars_raw_list`
+#' @export
+as_polars_series.rpolars_raw_list = function(x, name = NULL, ...) {
+  as_polars_series.default(x, name = name)
+}

tests/testthat/test-as_polars.R

@@ -427,3 +427,16 @@ test_that("clock_zoned_time may returns empty time zone", {
 
   expect_s3_class(as_polars_series(clock::zoned_time_now(zone = "")), "RPolarsSeries")
 })
+
+
+test_that("as_polars_series for nested type", {
+  expect_true(
+    as_polars_series(list(list(data.frame(a = 1))))$dtype == pl$List(pl$List(pl$Struct(a = pl$Float64)))
+  )
+
+  # TODO: this shouldn't error
+  expect_grepl_error(
+    as_polars_series(list(as_polars_series(NULL), as_polars_series(1L))),
+    "One element was null and another was i32"
+  )
+})

tests/testthat/test-expr_list.R

@@ -1,5 +1,5 @@
 test_that("list$len", {
-  df = pl$DataFrame(list_of_strs = as_polars_series(list(c("a", "b"), "c", character(), list(), NULL)))
+  df = pl$DataFrame(list_of_strs = as_polars_series(list(c("a", "b"), "c", character(), NULL, NULL)))
   l = df$with_columns(pl$col("list_of_strs")$list$len()$alias("list_of_strs_lengths"))$to_list()
 
   expect_identical(