GH-676 : Corrected DtypeArg for accepting strings (#680)

* GH-676

* Update test_io.py

* Update tests/test_io.py

Co-authored-by: Irv Lustig <irv@princeton.com>

* Update test_io.py

---------

Co-authored-by: Irv Lustig <irv@princeton.com>

Author: ramvikrams

pandas-stubs/_typing.pyi

@@ -76,7 +76,7 @@ class FulldatetimeDict(YearMonthDayDict, total=False):
 # dtypes
 NpDtype: TypeAlias = str | np.dtype[np.generic] | type[str | complex | bool | object]
 Dtype: TypeAlias = ExtensionDtype | NpDtype
-DtypeArg: TypeAlias = Dtype | dict[Any, Dtype]
+DtypeArg: TypeAlias = Dtype | Mapping[Any, Dtype]
 DtypeBackend: TypeAlias = Literal["pyarrow", "numpy_nullable"]
 BooleanDtypeArg: TypeAlias = (
     # Builtin bool type and its string alias

tests/test_io.py

@@ -1388,3 +1388,23 @@ def test_read_with_lxml_dtype_backend() -> None:
         check(
             assert_type(read_xml(path, dtype_backend="pyarrow"), DataFrame), DataFrame
         )
+
+
+def test_read_sql_dict_str_value_dtype() -> None:
+    # GH 676
+    with ensure_clean() as path:
+        con = sqlite3.connect(path)
+        check(assert_type(DF.to_sql("test", con), Union[int, None]), int)
+        check(
+            assert_type(
+                read_sql_query(
+                    "select * from test",
+                    con=con,
+                    index_col="index",
+                    dtype={"a": "int"},
+                ),
+                DataFrame,
+            ),
+            DataFrame,
+        )
+        con.close()