test: Add tests for fixed open issues (#21185)

py-polars/tests/unit/operations/map/test_map_elements.py

@@ -2,7 +2,7 @@
 
 import json
 from datetime import date, datetime, timedelta
-from typing import Any
+from typing import Any, NamedTuple
 
 import numpy as np
 import pytest
@@ -384,3 +384,18 @@ def test_map_elements_list_return_dtype() -> None:
     )
     expected = pl.Series([[2], [3, 4]], dtype=return_dtype)
     assert_series_equal(result, expected)
+
+
+def test_map_elements_list_of_named_tuple_15425() -> None:
+    class Foo(NamedTuple):
+        x: int
+
+    df = pl.DataFrame({"a": [0, 1, 2]})
+    result = df.select(
+        pl.col("a").map_elements(
+            lambda x: [Foo(i) for i in range(x)],
+            return_dtype=pl.List(pl.Struct({"x": pl.Int64})),
+        )
+    )
+    expected = pl.DataFrame({"a": [[], [{"x": 0}], [{"x": 0}, {"x": 1}]]})
+    assert_frame_equal(result, expected)

py-polars/tests/unit/operations/test_fill_null.py

@@ -91,3 +91,14 @@ def test_fill_null_int_dtype_15546() -> None:
     result = df.fill_null(0).collect()
     expected = pl.Series("a", [1, 2, 0], dtype=pl.Int8).to_frame()
     assert_frame_equal(result, expected)
+
+
+def test_fill_null_with_list_10869() -> None:
+    assert_series_equal(
+        pl.Series([[1], None]).fill_null([2]),
+        pl.Series([[1], [2]]),
+    )
+
+    match = "failed to determine supertype"
+    with pytest.raises(pl.exceptions.SchemaError, match=match):
+        pl.Series([1, None]).fill_null([2])

py-polars/tests/unit/operations/test_join.py

@@ -1700,3 +1700,16 @@ def test_join_on_struct() -> None:
             c=pl.Series([4, 2, 4, 2, 4, 2]),
         ),
     )
+
+
+def test_empty_join_result_with_array_15474() -> None:
+    lhs = pl.DataFrame(
+        {
+            "x": [1, 2],
+            "y": pl.Series([[1, 2, 3], [4, 5, 6]], dtype=pl.Array(pl.Int64, 3)),
+        }
+    )
+    rhs = pl.DataFrame({"x": [0]})
+    result = lhs.join(rhs, on="x")
+    expected = pl.DataFrame(schema={"x": pl.Int64, "y": pl.Array(pl.Int64, 3)})
+    assert_frame_equal(result, expected)

py-polars/tests/unit/streaming/test_streaming_io.py

@@ -322,3 +322,13 @@ def test_nyi_scan_in_memory(method: str) -> None:
         match="not yet implemented: Streaming scanning of in-memory buffers",
     ):
         (getattr(pl, f"scan_{method}"))(f).collect(streaming=True)
+
+
+def test_empty_sink_parquet_join_14863(tmp_path: Path) -> None:
+    file_path = tmp_path / "empty.parquet"
+    lf = pl.LazyFrame(schema=["a", "b", "c"]).cast(pl.String)
+    lf.sink_parquet(file_path)
+    assert_frame_equal(
+        pl.LazyFrame({"a": ["uno"]}).join(pl.scan_parquet(file_path), on="a").collect(),
+        lf.collect(),
+    )