Concatenate to support Ellipsis argument

CHANGELOG.md

@@ -16,6 +16,8 @@
   subscripted objects) had wrong parameters if they were directly
   subscripted with an `Unpack` object.
   Patch by [Daraan](https://github.com/Daraan).
+- Extended the Concatenate backport for Python 3.8-3.10 to now accept
+  ellipsis as an argument. Patch by [Daraan](https://github.com/Daraan).
 
 # Release 4.12.2 (June 7, 2024)
 

doc/index.rst

@@ -178,7 +178,7 @@ Special typing primitives
    See :py:data:`typing.Concatenate` and :pep:`612`. In ``typing`` since 3.10.
 
    The backport does not support certain operations involving ``...`` as
-   a parameter; see :issue:`48` and :issue:`110` for details.
+   a parameter; see :issue:`48` and :pr:`481` for details.
 
 .. data:: Final
 

src/test_typing_extensions.py

@@ -1720,12 +1720,15 @@ class C(Generic[T]): pass
         # In 3.9 and lower we use typing_extensions's hacky implementation
         # of ParamSpec, which gets incorrectly wrapped in a list
         self.assertIn(get_args(Callable[P, int]), [(P, int), ([P], int)])
-        self.assertEqual(get_args(Callable[Concatenate[int, P], int]),
-                         (Concatenate[int, P], int))
         self.assertEqual(get_args(Required[int]), (int,))
         self.assertEqual(get_args(NotRequired[int]), (int,))
         self.assertEqual(get_args(Unpack[Ts]), (Ts,))
         self.assertEqual(get_args(Unpack), ())
+        self.assertEqual(get_args(Callable[Concatenate[int, P], int]),
+                         (Concatenate[int, P], int))
+        with self.subTest("Concatenate[int, ...]"):
+            self.assertEqual(get_args(Callable[Concatenate[int, ...], int]),
+                        (Concatenate[int, ...], int))
 
 
 class CollectionsAbcTests(BaseTestCase):
@@ -5267,6 +5270,10 @@ class Y(Protocol[T, P]):
                 self.assertEqual(G2.__args__, (int, Concatenate[int, P_2]))
                 self.assertEqual(G2.__parameters__, (P_2,))
 
+                G3 = klass[int, Concatenate[int, ...]]
+                self.assertEqual(G3.__args__, (int, Concatenate[int, ...]))
+                self.assertEqual(G3.__parameters__, ())
+
         # The following are some valid uses cases in PEP 612 that don't work:
         # These do not work in 3.9, _type_check blocks the list and ellipsis.
         # G3 = X[int, [int, bool]]
@@ -5362,6 +5369,11 @@ class MyClass: ...
         c = Concatenate[MyClass, P]
         self.assertNotEqual(c, Concatenate)
 
+        # Test Ellipsis Concatenation
+        d = Concatenate[MyClass, ...]
+        self.assertNotEqual(d, c)
+        self.assertNotEqual(d, Concatenate)
+
     def test_valid_uses(self):
         P = ParamSpec('P')
         T = TypeVar('T')
@@ -5371,13 +5383,27 @@ def test_valid_uses(self):
         self.assertEqual(C1.__origin__, C2.__origin__)
         self.assertNotEqual(C1, C2)
 
-        # Test collections.abc.Callable too.
-        if sys.version_info[:2] >= (3, 9):
-            C3 = collections.abc.Callable[Concatenate[int, P], int]
-            C4 = collections.abc.Callable[Concatenate[int, T, P], T]
+        with self.subTest("typing.Callable with Ellipsis"):
+            C3 = Callable[Concatenate[int, ...], int]
+            C4 = Callable[Concatenate[int, T, ...], T]
             self.assertEqual(C3.__origin__, C4.__origin__)
             self.assertNotEqual(C3, C4)
 
+    @skipUnless(TYPING_3_9_0, "Needs PEP 585")
+    def test_pep585_collections_callable(self):
+        P = ParamSpec('P')
+        T = TypeVar('T')
+        # Test collections.abc.Callable too.
+        C5 = collections.abc.Callable[Concatenate[int, P], int]
+        C6 = collections.abc.Callable[Concatenate[int, T, P], T]
+        self.assertEqual(C5.__origin__, C6.__origin__)
+        self.assertNotEqual(C5, C6)
+
+        C7 = collections.abc.Callable[Concatenate[int, ...], int]
+        C8 = collections.abc.Callable[Concatenate[int, T, ...], T]
+        self.assertEqual(C7.__origin__, C8.__origin__)
+        self.assertNotEqual(C7, C8)
+
     def test_invalid_uses(self):
         P = ParamSpec('P')
         T = TypeVar('T')
@@ -5390,25 +5416,50 @@ def test_invalid_uses(self):
 
         with self.assertRaisesRegex(
             TypeError,
-            'The last parameter to Concatenate should be a ParamSpec variable',
+            'The last parameter to Concatenate should be a ParamSpec variable or ellipsis',
         ):
             Concatenate[P, T]
 
-        if not TYPING_3_11_0:
-            with self.assertRaisesRegex(
-                TypeError,
-                'each arg must be a type',
-            ):
-                Concatenate[1, P]
+        with self.assertRaisesRegex(
+            TypeError,
+            'is not a generic class',
+        ):
+            Callable[Concatenate[int, ...], Any][Any]
+
+    def test_invalid_use(self):
+        # Assure that `_type_check` is called.
+        P = ParamSpec('P')
+        with self.assertRaisesRegex(
+            TypeError,
+            "each arg must be a type",
+        ):
+            Concatenate[(str,), P]
+
+    @skipUnless(TYPING_3_11_0 or (3, 10, 0) <= sys.version_info < (3, 10, 2),
+                "Cannot be backported to <=3.9. See issue #48"
+                "Cannot use ... with typing._ConcatenateGenericAlias after 3.10.2")
+    def test_alias_subscription_with_ellipsis(self):
+        P = ParamSpec('P')
+        X = Callable[Concatenate[int, P], Any]
+
+        C1 = X[...]
+        self.assertEqual(C1.__parameters__, ())
+        self.assertEqual(get_args(C1), (Concatenate[int, ...], Any))
 
     def test_basic_introspection(self):
         P = ParamSpec('P')
         C1 = Concatenate[int, P]
         C2 = Concatenate[int, T, P]
+        C3 = Concatenate[int, ...]
+        C4 = Concatenate[int, T, ...]
         self.assertEqual(C1.__origin__, Concatenate)
         self.assertEqual(C1.__args__, (int, P))
         self.assertEqual(C2.__origin__, Concatenate)
         self.assertEqual(C2.__args__, (int, T, P))
+        self.assertEqual(C3.__origin__, Concatenate)
+        self.assertEqual(C3.__args__, (int, Ellipsis))
+        self.assertEqual(C4.__origin__, Concatenate)
+        self.assertEqual(C4.__args__, (int, T, Ellipsis))
 
     def test_eq(self):
         P = ParamSpec('P')
@@ -5419,6 +5470,13 @@ def test_eq(self):
         self.assertEqual(hash(C1), hash(C2))
         self.assertNotEqual(C1, C3)
 
+        C4 = Concatenate[int, ...]
+        C5 = Concatenate[int, ...]
+        C6 = Concatenate[int, T, ...]
+        self.assertEqual(C4, C5)
+        self.assertEqual(hash(C4), hash(C5))
+        self.assertNotEqual(C4, C6)
+
 
 class TypeGuardTests(BaseTestCase):
     def test_basics(self):
@@ -6089,7 +6147,7 @@ def test_typing_extensions_defers_when_possible(self):
         if sys.version_info < (3, 10, 1):
             exclude |= {"Literal"}
         if sys.version_info < (3, 11):
-            exclude |= {'final', 'Any', 'NewType', 'overload'}
+            exclude |= {'final', 'Any', 'NewType', 'overload', 'Concatenate'}
         if sys.version_info < (3, 12):
             exclude |= {
                 'SupportsAbs', 'SupportsBytes',

src/typing_extensions.py

@@ -1795,28 +1795,56 @@ def __parameters__(self):
             return tuple(
                 tp for tp in self.__args__ if isinstance(tp, (typing.TypeVar, ParamSpec))
             )
+# 3.10+
+else:
+    _ConcatenateGenericAlias = typing._ConcatenateGenericAlias
 
+# 3.8-3.9.2
+class _EllipsisDummy: ...
+
+# 3.8-3.10
+def _create_concatenate_alias(origin, parameters):
+    if parameters[-1] is ... and sys.version_info < (3, 9, 2):
+        # Hack: Arguments must be types, replace it with one.
+        parameters = parameters[:-1] + (_EllipsisDummy,)
+    if sys.version_info >= (3, 10, 2):
+        concatenate = _ConcatenateGenericAlias(origin, parameters,
+                                        _typevar_types=(TypeVar, ParamSpec),
+                                        _paramspec_tvars=True)
+    else:
+        concatenate = _ConcatenateGenericAlias(origin, parameters)
+    if parameters[-1] is not _EllipsisDummy:
+        return concatenate
+    # Remove dummy again
+    concatenate.__args__ = tuple(p if p is not _EllipsisDummy else ...
+                                    for p in concatenate.__args__)
+    if sys.version_info < (3, 10):
+        # backport needs __args__ adjustment only
+        return concatenate
+    concatenate.__parameters__ = tuple(p for p in concatenate.__parameters__
+                                        if p is not _EllipsisDummy)
+    return concatenate
 
-# 3.8-3.9
+
+# 3.8-3.10
 @typing._tp_cache
 def _concatenate_getitem(self, parameters):
     if parameters == ():
         raise TypeError("Cannot take a Concatenate of no types.")
     if not isinstance(parameters, tuple):
         parameters = (parameters,)
-    if not isinstance(parameters[-1], ParamSpec):
+    if not (parameters[-1] is ... or isinstance(parameters[-1], ParamSpec)):
         raise TypeError("The last parameter to Concatenate should be a "
-                        "ParamSpec variable.")
+                        "ParamSpec variable or ellipsis.")
     msg = "Concatenate[arg, ...]: each arg must be a type."
-    parameters = tuple(typing._type_check(p, msg) for p in parameters)
-    return _ConcatenateGenericAlias(self, parameters)
-
+    parameters = (*(typing._type_check(p, msg) for p in parameters[:-1]),
+                    parameters[-1])
+    return _create_concatenate_alias(self, parameters)
 
-# 3.10+
-if hasattr(typing, 'Concatenate'):
+# 3.11+; Concatenate does not accept ellipsis in 3.10
+if hasattr(typing, 'Concatenate') and sys.version_info >= (3, 11):
     Concatenate = typing.Concatenate
-    _ConcatenateGenericAlias = typing._ConcatenateGenericAlias
-# 3.9
+# 3.9-3.10
 elif sys.version_info[:2] >= (3, 9):
     @_ExtensionsSpecialForm
     def Concatenate(self, parameters):