Backport PR #51302 on branch 2.0.x (ENH: Enable more Arrow CSV tests/…

…features) (#51998)

Backport PR #51302: ENH: Enable more Arrow CSV tests/features

Co-authored-by: Thomas Li <47963215+lithomas1@users.noreply.github.com>

doc/source/whatsnew/v2.0.0.rst

@@ -270,6 +270,7 @@ Other enhancements
 - :func:`to_datetime` now accepts ``"mixed"`` as an argument to ``format``, which will infer the format for each element individually (:issue:`50972`)
 - Added new argument ``engine`` to :func:`read_json` to support parsing JSON with pyarrow by specifying ``engine="pyarrow"`` (:issue:`48893`)
 - Added support for SQLAlchemy 2.0 (:issue:`40686`)
+- Added support for ``decimal`` parameter when ``engine="pyarrow"`` in :func:`read_csv` (:issue:`51302`)
 - :class:`Index` set operations :meth:`Index.union`, :meth:`Index.intersection`, :meth:`Index.difference`, and :meth:`Index.symmetric_difference` now support ``sort=True``, which will always return a sorted result, unlike the default ``sort=None`` which does not sort in some cases (:issue:`25151`)
 
 .. ---------------------------------------------------------------------------
@@ -1284,6 +1285,7 @@ I/O
 - Bug in :meth:`DataFrame.to_json` where it would segfault when failing to encode a string (:issue:`50307`)
 - Bug in :meth:`DataFrame.to_html` with ``na_rep`` set when the :class:`DataFrame` contains non-scalar data (:issue:`47103`)
 - Bug in :func:`read_xml` where file-like objects failed when iterparse is used (:issue:`50641`)
+- Bug in :func:`read_csv` when ``engine="pyarrow"`` where ``encoding`` parameter was not handled correctly (:issue:`51302`)
 - Bug in :func:`read_xml` ignored repeated elements when iterparse is used (:issue:`51183`)
 - Bug in :class:`ExcelWriter` leaving file handles open if an exception occurred during instantiation (:issue:`51443`)
 

pandas/io/parsers/arrow_parser_wrapper.py

@@ -50,6 +50,7 @@ def _get_pyarrow_options(self) -> None:
             "na_values": "null_values",
             "escapechar": "escape_char",
             "skip_blank_lines": "ignore_empty_lines",
+            "decimal": "decimal_point",
         }
         for pandas_name, pyarrow_name in mapping.items():
             if pandas_name in self.kwds and self.kwds.get(pandas_name) is not None:
@@ -67,13 +68,20 @@ def _get_pyarrow_options(self) -> None:
             for option_name, option_value in self.kwds.items()
             if option_value is not None
             and option_name
-            in ("include_columns", "null_values", "true_values", "false_values")
+            in (
+                "include_columns",
+                "null_values",
+                "true_values",
+                "false_values",
+                "decimal_point",
+            )
         }
         self.read_options = {
             "autogenerate_column_names": self.header is None,
             "skip_rows": self.header
             if self.header is not None
             else self.kwds["skiprows"],
+            "encoding": self.encoding,
         }
 
     def _finalize_pandas_output(self, frame: DataFrame) -> DataFrame:

pandas/io/parsers/readers.py

@@ -455,7 +455,6 @@
     "quoting",
     "lineterminator",
     "converters",
-    "decimal",
     "iterator",
     "dayfirst",
     "verbose",

pandas/tests/io/parser/common/test_decimal.py

@@ -9,9 +9,10 @@
 from pandas import DataFrame
 import pandas._testing as tm
 
-pytestmark = pytest.mark.usefixtures("pyarrow_skip")
+xfail_pyarrow = pytest.mark.usefixtures("pyarrow_xfail")
 
 
+@xfail_pyarrow
 @pytest.mark.parametrize(
     "data,thousands,decimal",
     [

pandas/tests/io/parser/dtypes/test_categorical.py

@@ -118,7 +118,6 @@ def test_categorical_dtype_high_cardinality_numeric(all_parsers):
     tm.assert_frame_equal(actual, expected)
 
 
-@xfail_pyarrow
 def test_categorical_dtype_utf16(all_parsers, csv_dir_path):
     # see gh-10153
     pth = os.path.join(csv_dir_path, "utf16_ex.txt")

pandas/tests/io/parser/test_encoding.py

@@ -20,9 +20,9 @@
 import pandas._testing as tm
 
 skip_pyarrow = pytest.mark.usefixtures("pyarrow_skip")
+xfail_pyarrow = pytest.mark.usefixtures("pyarrow_xfail")
 
 
-@skip_pyarrow
 def test_bytes_io_input(all_parsers):
     encoding = "cp1255"
     parser = all_parsers
@@ -44,7 +44,7 @@ def test_read_csv_unicode(all_parsers):
     tm.assert_frame_equal(result, expected)
 
 
-@skip_pyarrow
+@xfail_pyarrow
 @pytest.mark.parametrize("sep", [",", "\t"])
 @pytest.mark.parametrize("encoding", ["utf-16", "utf-16le", "utf-16be"])
 def test_utf16_bom_skiprows(all_parsers, sep, encoding):
@@ -73,15 +73,13 @@ def test_utf16_bom_skiprows(all_parsers, sep, encoding):
         tm.assert_frame_equal(result, expected)
 
 
-@skip_pyarrow
 def test_utf16_example(all_parsers, csv_dir_path):
     path = os.path.join(csv_dir_path, "utf16_ex.txt")
     parser = all_parsers
     result = parser.read_csv(path, encoding="utf-16", sep="\t")
     assert len(result) == 50
 
 
-@skip_pyarrow
 def test_unicode_encoding(all_parsers, csv_dir_path):
     path = os.path.join(csv_dir_path, "unicode_series.csv")
     parser = all_parsers
@@ -94,7 +92,6 @@ def test_unicode_encoding(all_parsers, csv_dir_path):
     assert got == expected
 
 
-@skip_pyarrow
 @pytest.mark.parametrize(
     "data,kwargs,expected",
     [
@@ -114,7 +111,7 @@ def test_unicode_encoding(all_parsers, csv_dir_path):
         ),
     ],
 )
-def test_utf8_bom(all_parsers, data, kwargs, expected):
+def test_utf8_bom(all_parsers, data, kwargs, expected, request):
     # see gh-4793
     parser = all_parsers
     bom = "\ufeff"
@@ -124,11 +121,20 @@ def _encode_data_with_bom(_data):
         bom_data = (bom + _data).encode(utf8)
         return BytesIO(bom_data)
 
+    if (
+        parser.engine == "pyarrow"
+        and data == "\n1"
+        and kwargs.get("skip_blank_lines", True)
+    ):
+        # Manually xfail, since we don't have mechanism to xfail specific version
+        request.node.add_marker(
+            pytest.mark.xfail(reason="Pyarrow can't read blank lines")
+        )
+
     result = parser.read_csv(_encode_data_with_bom(data), encoding=utf8, **kwargs)
     tm.assert_frame_equal(result, expected)
 
 
-@skip_pyarrow
 def test_read_csv_utf_aliases(all_parsers, utf_value, encoding_fmt):
     # see gh-13549
     expected = DataFrame({"mb_num": [4.8], "multibyte": ["test"]})
@@ -141,7 +147,6 @@ def test_read_csv_utf_aliases(all_parsers, utf_value, encoding_fmt):
     tm.assert_frame_equal(result, expected)
 
 
-@skip_pyarrow
 @pytest.mark.parametrize(
     "file_path,encoding",
     [
@@ -226,7 +231,7 @@ def test_parse_encoded_special_characters(encoding):
     tm.assert_frame_equal(result, expected)
 
 
-@skip_pyarrow
+@xfail_pyarrow
 @pytest.mark.parametrize("encoding", ["utf-8", None, "utf-16", "cp1255", "latin-1"])
 def test_encoding_memory_map(all_parsers, encoding):
     # GH40986
@@ -244,7 +249,7 @@ def test_encoding_memory_map(all_parsers, encoding):
     tm.assert_frame_equal(df, expected)
 
 
-@skip_pyarrow
+@xfail_pyarrow
 def test_chunk_splits_multibyte_char(all_parsers):
     """
     Chunk splits a multibyte character with memory_map=True
@@ -264,7 +269,7 @@ def test_chunk_splits_multibyte_char(all_parsers):
     tm.assert_frame_equal(dfr, df)
 
 
-@skip_pyarrow
+@xfail_pyarrow
 def test_readcsv_memmap_utf8(all_parsers):
     """
     GH 43787