Fix _csv.Dialect.__init__ (#12320)

stdlib/@tests/stubtest_allowlists/common.txt

@@ -11,7 +11,6 @@ _collections_abc.AsyncGenerator.ag_running
 _collections_abc.ItemsView.__reversed__
 _collections_abc.KeysView.__reversed__
 _collections_abc.ValuesView.__reversed__
-_csv.Dialect.__init__ # C __init__ signature is inaccurate
 _ctypes.CFuncPtr # stubtest erroneously thinks it can't be subclassed
 _threading_local.local.__new__
 ast.Bytes.__new__

stdlib/_csv.pyi

@@ -20,6 +20,8 @@ _QuotingType: TypeAlias = int
 
 class Error(Exception): ...
 
+_DialectLike: TypeAlias = str | Dialect | type[Dialect]
+
 class Dialect:
  delimiter: str
  quotechar: str | None
@@ -29,9 +31,18 @@ class Dialect:
  lineterminator: str
  quoting: _QuotingType
  strict: bool
- def __init__(self) -> None: ...
-
-_DialectLike: TypeAlias = str | Dialect | type[Dialect]
+ def __init__(
+ self,
+ dialect: _DialectLike | None = ...,
+ delimiter: str = ",",
+ doublequote: bool = True,
+ escapechar: str | None = None,
+ lineterminator: str = "\r\n",
+ quotechar: str | None = '"',
+ quoting: _QuotingType = 0,
+ skipinitialspace: bool = False,
+ strict: bool = False,
+ ) -> None: ...
 
 class _reader(Iterator[list[str]]):
  @property

stdlib/csv.pyi

@@ -1,12 +1,10 @@
 import sys
-
-# actually csv.Dialect is a different class to _csv.Dialect at runtime, but for typing purposes, they're identical
 from _csv import (
  QUOTE_ALL as QUOTE_ALL,
  QUOTE_MINIMAL as QUOTE_MINIMAL,
  QUOTE_NONE as QUOTE_NONE,
  QUOTE_NONNUMERIC as QUOTE_NONNUMERIC,
- Dialect as Dialect,
+ Dialect as _Dialect,
  Error as Error,
  __version__ as __version__,
  _DialectLike,
@@ -61,6 +59,9 @@ if sys.version_info < (3, 13):
 
 _T = TypeVar("_T")
 
+class Dialect(_Dialect):
+ def __init__(self) -> None: ...
+
 class excel(Dialect): ...
 class excel_tab(excel): ...
 class unix_dialect(Dialect): ...