Implement support for PEP 764 (inline typed dictionaries) #580

Viicos · 2025-04-07T19:18:54Z

Only downside is that the parent frame to be fetched is different depending on which syntax (functional or inline) is used. This means we need an extra argument (called __typing_is_inline__ in this PR) to differentiate the two. This isn't required in #579.

There are also some issues on 3.8:

_ensure_subclassable() assumes it applies on functions on pypy for Python 3.8:

typing_extensions/src/typing_extensions.py

Lines 866 to 878 in 281d7b0

    
           def _ensure_subclassable(mro_entries): 
        
               def inner(func): 
        
                   if sys.implementation.name == "pypy" and sys.version_info < (3, 9): 
        
                       cls_dict = { 
        
                           "__call__": staticmethod(func), 
        
                           "__mro_entries__": staticmethod(mro_entries) 
        
                       } 
        
                       t = type(func.__name__, (), cls_dict) 
        
                       return functools.update_wrapper(t(), func) 
        
                   else: 
        
                       func.__mro_entries__ = mro_entries 
        
                       return func 
        
               return inner

which isn't the case here (the decorator is applied on the _TypedDictSpecialForm instance).

typing._SpecialForm is implemented quite differently on 3.8, so we would need to redefine __getitem__() on _TypedDictSpecialForm.

~~Maybe support for 3.8 should be dropped first.~~ done in #585.

src/typing_extensions.py

AlexWaygood · 2025-04-19T22:54:04Z

I would be tempted to move the complexity out of _TypedDictSpecialForm.__call__ into a separate function. It means that you can keep the __typing_is_inline__ parameter out of _TypedDictSpecialForm.__call__, which means that it doesn't show up when users do inspect.signature(TypedDict).

Currently on this PR we get the following:

>>> from typing_extensions import TypedDict
>>> import inspect
>>> inspect.signature(TypedDict)
<Signature (typename, fields=<sentinel>, /, *, total=True, closed=None, extra_items=typing_extensions.NoExtraItems, __typing_is_inline__=False, **kwargs)>

but if you made this change:

Suggested patch

diff --git a/src/typing_extensions.py b/src/typing_extensions.py
index 9c727a8..dfbaa7d 100644
--- a/src/typing_extensions.py
+++ b/src/typing_extensions.py
@@ -1079,6 +1079,68 @@ else:
     _TypedDict = type.__new__(_TypedDictMeta, 'TypedDict', (), {})
 
 
+    def _create_typeddict(
+        typename,
+        fields,
+        /,
+        *,
+        typing_is_inline,
+        total,
+        closed,
+        extra_items,
+        **kwargs
+    ):
+        if fields is _marker or fields is None:
+            if fields is _marker:
+                deprecated_thing = (
+                    "Failing to pass a value for the 'fields' parameter"
+                )
+            else:
+                deprecated_thing = "Passing `None` as the 'fields' parameter"
+
+            example = f"`{typename} = TypedDict({typename!r}, {{}})`"
+            deprecation_msg = (
+                f"{deprecated_thing} is deprecated and will be disallowed in "
+                "Python 3.15. To create a TypedDict class with 0 fields "
+                "using the functional syntax, pass an empty dictionary, e.g. "
+            ) + example + "."
+            warnings.warn(deprecation_msg, DeprecationWarning, stacklevel=2)
+            # Support a field called "closed"
+            if closed is not False and closed is not True and closed is not None:
+                kwargs["closed"] = closed
+                closed = None
+            # Or "extra_items"
+            if extra_items is not NoExtraItems:
+                kwargs["extra_items"] = extra_items
+                extra_items = NoExtraItems
+            fields = kwargs
+        elif kwargs:
+            raise TypeError("TypedDict takes either a dict or keyword arguments,"
+                            " but not both")
+        if kwargs:
+            if sys.version_info >= (3, 13):
+                raise TypeError("TypedDict takes no keyword arguments")
+            warnings.warn(
+                "The kwargs-based syntax for TypedDict definitions is deprecated "
+                "in Python 3.11, will be removed in Python 3.13, and may not be "
+                "understood by third-party type checkers.",
+                DeprecationWarning,
+                stacklevel=2,
+            )
+
+        ns = {'__annotations__': dict(fields)}
+        module = _caller(depth=5 if typing_is_inline else 3)
+        if module is not None:
+            # Setting correct module is necessary to make typed dict classes
+            # pickleable.
+            ns['__module__'] = module
+
+        td = _TypedDictMeta(typename, (), ns, total=total, closed=closed,
+                            extra_items=extra_items)
+        td.__orig_bases__ = (TypedDict,)
+        return td
+
+
     class _TypedDictSpecialForm(_ExtensionsSpecialForm, _root=True):
         def __call__(
             self,
@@ -1089,60 +1151,22 @@ else:
             total=True,
             closed=None,
             extra_items=NoExtraItems,
-            __typing_is_inline__=False,
             **kwargs
         ):
-            if fields is _marker or fields is None:
-                if fields is _marker:
-                    deprecated_thing = (
-                        "Failing to pass a value for the 'fields' parameter"
-                    )
-                else:
-                    deprecated_thing = "Passing `None` as the 'fields' parameter"
-
-                example = f"`{typename} = TypedDict({typename!r}, {{}})`"
-                deprecation_msg = (
-                    f"{deprecated_thing} is deprecated and will be disallowed in "
-                    "Python 3.15. To create a TypedDict class with 0 fields "
-                    "using the functional syntax, pass an empty dictionary, e.g. "
-                ) + example + "."
-                warnings.warn(deprecation_msg, DeprecationWarning, stacklevel=2)
-                # Support a field called "closed"
-                if closed is not False and closed is not True and closed is not None:
-                    kwargs["closed"] = closed
-                    closed = None
-                # Or "extra_items"
-                if extra_items is not NoExtraItems:
-                    kwargs["extra_items"] = extra_items
-                    extra_items = NoExtraItems
-                fields = kwargs
-            elif kwargs:
-                raise TypeError("TypedDict takes either a dict or keyword arguments,"
-                                " but not both")
-            if kwargs:
-                if sys.version_info >= (3, 13):
-                    raise TypeError("TypedDict takes no keyword arguments")
-                warnings.warn(
-                    "The kwargs-based syntax for TypedDict definitions is deprecated "
-                    "in Python 3.11, will be removed in Python 3.13, and may not be "
-                    "understood by third-party type checkers.",
-                    DeprecationWarning,
-                    stacklevel=2,
-                )
+            return _create_typeddict(
+                typename,
+                fields,
+                total=total,
+                closed=closed,
+                extra_items=extra_items,
+                typing_is_inline=False,
+                **kwargs
+            )
 
-            ns = {'__annotations__': dict(fields)}
-            module = _caller(depth=5 if __typing_is_inline__ else 2)
-            if module is not None:
-                # Setting correct module is necessary to make typed dict classes
-                # pickleable.
-                ns['__module__'] = module
+        def __mro_entries__(self, bases):
+            return (_TypedDict,)
 
-            td = _TypedDictMeta(typename, (), ns, total=total, closed=closed,
-                                extra_items=extra_items)
-            td.__orig_bases__ = (TypedDict,)
-            return td
 
-    @_ensure_subclassable(lambda bases: (_TypedDict,))
     @_TypedDictSpecialForm
     def TypedDict(self, args):
         """A simple typed namespace. At runtime it is equivalent to a plain dict.
@@ -1198,9 +1222,14 @@ else:
             raise TypeError(
                 "TypedDict[...] should be used with a single dict argument"
             )
-
-        # Delegate to _TypedDictSpecialForm.__call__:
-        return self("<inlined TypedDict>", args[0], __typing_is_inline__=True)
+        return _create_typeddict(
+            "<inlined TypedDict>",
+            args[0],
+            typing_is_inline=True,
+            total=True,
+            closed=None,
+            extra_items=NoExtraItems
+        )

Then it would look like this:

>>> from typing_extensions import TypedDict
>>> import inspect
>>> inspect.signature(TypedDict)
<Signature (typename, fields=<sentinel>, /, *, total=True, closed=None, extra_items=typing_extensions.NoExtraItems, **kwargs)>
>>> exit()

(and all your tests still pass with that diff applied!)

AlexWaygood

This looks great. A couple more minor comments:

src/test_typing_extensions.py

src/typing_extensions.py

AlexWaygood

LGTM, thank you! Can you add an entry to CHANGELOG.md?

src/test_typing_extensions.py

src/typing_extensions.py

src/test_typing_extensions.py

Viicos force-pushed the pep-764-2 branch from 5721db9 to 2fe24f0 Compare April 7, 2025 19:35

This was referenced Apr 7, 2025

Implement support for PEP 764 (inline typed dictionaries) #579

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Drop support for Python 3.8 #568

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Viicos force-pushed the pep-764-2 branch from 2fe24f0 to 6c1113b Compare April 17, 2025 07:30

Implement support for PEP 764 (inline typed dictionaries)

7379a2a

Viicos force-pushed the pep-764-2 branch from 6c1113b to 7379a2a Compare April 18, 2025 07:27

AlexWaygood reviewed Apr 19, 2025

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Viicos added 2 commits April 23, 2025 09:54

Define _create_typeddict(), change __name__

9532f11

Get rid of _ensure_subclassable()

3cd8f9e

Viicos changed the title ~~Implement support for PEP 764 (alternative implementation)~~ Implement support for PEP 764 (inline typed dictionaries) Apr 23, 2025

AlexWaygood reviewed Apr 23, 2025

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Viicos added 2 commits April 24, 2025 10:51

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Do not support tuple

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AlexWaygood merged commit 28f08ac into python:main Apr 25, 2025
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[red-knot] No errors for definitions of TypedDicts astral-sh/ruff#17674

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Implement support for PEP 764 (inline typed dictionaries) #580

Implement support for PEP 764 (inline typed dictionaries) #580

Viicos commented Apr 7, 2025 •

edited

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AlexWaygood commented Apr 19, 2025

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	def _ensure_subclassable(mro_entries):
	def inner(func):
	if sys.implementation.name == "pypy" and sys.version_info < (3, 9):
	cls_dict = {
	"__call__": staticmethod(func),
	"__mro_entries__": staticmethod(mro_entries)
	}
	t = type(func.__name__, (), cls_dict)
	return functools.update_wrapper(t(), func)
	else:
	func.__mro_entries__ = mro_entries
	return func
	return inner

Implement support for PEP 764 (inline typed dictionaries) #580

Implement support for PEP 764 (inline typed dictionaries) #580

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Viicos commented Apr 7, 2025 • edited Loading

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Viicos commented Apr 7, 2025 •

edited

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