Add backport for annotationlib.type_repr (#641)

Closes: #544

Co-authored-by: Brian Schubert <brianm.schubert@gmail.com>

Author: donbarbos

CHANGELOG.md

@@ -1,3 +1,11 @@
+# Unreleased
+
+- Add `typing_extensions.type_repr`, a backport of
+  [`annotationlib.type_repr`](https://docs.python.org/3.14/library/annotationlib.html#annotationlib.type_repr),
+  introduced in Python 3.14 (CPython PR [#124551](https://github.com/python/cpython/pull/124551),
+  originally by Jelle Zijlstra). Patch by Semyon Moroz.
+
+
 # Release 4.14.1 (July 4, 2025)
 
 - Fix usage of `typing_extensions.TypedDict` nested inside other types

doc/index.rst

@@ -933,6 +933,15 @@ Functions
 
    .. versionadded:: 4.1.0
 
+.. function:: type_repr(value)
+
+   See :py:func:`annotationlib.type_repr`. In ``annotationlib`` since 3.14.
+
+   Convert an arbitrary Python value to a format suitable for use by
+   the :attr:`Format.STRING`.
+
+   .. versionadded:: 4.15.0
+
 Enums
 ~~~~~
 

src/test_typing_extensions.py

@@ -101,6 +101,7 @@
     reveal_type,
     runtime,
     runtime_checkable,
+    type_repr,
 )
 
 NoneType = type(None)
@@ -8368,6 +8369,44 @@ def test_capsule_type(self):
         self.assertIsInstance(_datetime.datetime_CAPI, typing_extensions.CapsuleType)
 
 
+class MyClass:
+    def __repr__(self):
+        return "my repr"
+
+
+class TestTypeRepr(BaseTestCase):
+    def test_custom_types(self):
+
+        class Nested:
+            pass
+
+        def nested():
+            pass
+
+        self.assertEqual(type_repr(MyClass), f"{__name__}.MyClass")
+        self.assertEqual(
+            type_repr(Nested),
+            f"{__name__}.TestTypeRepr.test_custom_types.<locals>.Nested",
+        )
+        self.assertEqual(
+            type_repr(nested),
+            f"{__name__}.TestTypeRepr.test_custom_types.<locals>.nested",
+        )
+        self.assertEqual(type_repr(times_three), f"{__name__}.times_three")
+        self.assertEqual(type_repr(Format.VALUE), repr(Format.VALUE))
+        self.assertEqual(type_repr(MyClass()), "my repr")
+
+    def test_builtin_types(self):
+        self.assertEqual(type_repr(int), "int")
+        self.assertEqual(type_repr(object), "object")
+        self.assertEqual(type_repr(None), "None")
+        self.assertEqual(type_repr(len), "len")
+        self.assertEqual(type_repr(1), "1")
+        self.assertEqual(type_repr("1"), "'1'")
+        self.assertEqual(type_repr(''), "''")
+        self.assertEqual(type_repr(...), "...")
+
+
 def times_three(fn):
     @functools.wraps(fn)
     def wrapper(a, b):

src/typing_extensions.py

@@ -100,6 +100,7 @@
     'TypeGuard',
     'TypeIs',
     'TYPE_CHECKING',
+    'type_repr',
     'Never',
     'NoReturn',
     'ReadOnly',
@@ -4192,6 +4193,26 @@ def __getstate__(self):
         raise TypeError(f"Cannot pickle {type(self).__name__!r} object")
 
 
+if sys.version_info >= (3, 14, 0, "beta"):
+    type_repr = annotationlib.type_repr
+else:
+    def type_repr(value):
+        """Convert a Python value to a format suitable for use with the STRING format.
+
+        This is intended as a helper for tools that support the STRING format but do
+        not have access to the code that originally produced the annotations. It uses
+        repr() for most objects.
+
+        """
+        if isinstance(value, (type, _types.FunctionType, _types.BuiltinFunctionType)):
+            if value.__module__ == "builtins":
+                return value.__qualname__
+            return f"{value.__module__}.{value.__qualname__}"
+        if value is ...:
+            return "..."
+        return repr(value)
+
+
 # Aliases for items that are in typing in all supported versions.
 # We use hasattr() checks so this library will continue to import on
 # future versions of Python that may remove these names.