Preserve carriage returns in quoted CSV/TSV fields (#895)

When reading CSV or TSV files through rows_from_file() or the CLI insert command, io.TextIOWrapper defaulted to universal-newline mode (newline=None), causing carriage returns (\r\n or lone \r) embedded inside quoted fields to be silently translated to \n before csv.reader could process them.

Setting newline='' in TextIOWrapper preserves carriage returns in quoted fields according to the Python standard library csv module specification.

Fixes #895

tests/test_cli_insert.py

@@ -235,6 +235,21 @@ def test_insert_csv_tsv(content, options, db_path, tmpdir):
     assert [{"foo": "1", "bar": "2", "baz": "cat,dog"}] == list(db.table("data").rows)
 
 
+@pytest.mark.parametrize("fmt_opt", (["--csv"], ["--tsv"]))
+def test_insert_csv_tsv_preserves_carriage_returns_in_quoted_fields(fmt_opt, db_path):
+    delimiter = "\t" if "--tsv" in fmt_opt else ","
+    content = f'id{delimiter}v\r\n1{delimiter}"line1\r\nline2"\r\n'
+    result = CliRunner().invoke(
+        cli.cli,
+        ["insert", db_path, "data", "-"] + fmt_opt + ["--no-detect-types"],
+        catch_exceptions=False,
+        input=content.encode("utf-8"),
+    )
+    assert result.exit_code == 0
+    db = Database(db_path)
+    assert list(db.table("data").rows) == [{"id": "1", "v": "line1\r\nline2"}]
+
+
 @pytest.mark.parametrize("empty_null", (True, False))
 def test_insert_csv_empty_null(db_path, empty_null):
     options = ["--csv", "--no-detect-types"]

tests/test_rows_from_file.py

@@ -131,3 +131,31 @@ def test_detect_format_keeps_streaming_reader_open(
     assert not buffered_readers[0].closed
     assert len(list(rows)) == 2000
     assert buffered_readers[0].closed
+
+
+@pytest.mark.parametrize(
+    "file_bytes,expected_format,expected_rows",
+    [
+        (
+            b'id,v\r\n1,"line1\r\nline2"\r\n',
+            Format.CSV,
+            [{"id": "1", "v": "line1\r\nline2"}],
+        ),
+        (
+            b'id\tv\r\n1\t"tab1\r\ntab2"\r\n',
+            Format.TSV,
+            [{"id": "1", "v": "tab1\r\ntab2"}],
+        ),
+        (
+            b'id,v\r\n1,"isolated\rreturn"\r\n',
+            Format.CSV,
+            [{"id": "1", "v": "isolated\rreturn"}],
+        ),
+    ],
+)
+def test_rows_from_file_preserves_carriage_returns_in_quoted_fields(
+    file_bytes, expected_format, expected_rows
+):
+    rows, detected_format = rows_from_file(BytesIO(file_bytes), format=expected_format)
+    assert detected_format == expected_format
+    assert list(rows) == expected_rows