Reject duplicate ParamSpec.{args,kwargs} at call site (#18854)

Fixes #18035

Author: sterliakov

mypy/checkexpr.py

@@ -2357,7 +2357,8 @@ def check_argument_count(
 
         # Check for too many or few values for formals.
         for i, kind in enumerate(callee.arg_kinds):
-            if kind.is_required() and not formal_to_actual[i] and not is_unexpected_arg_error:
+            mapped_args = formal_to_actual[i]
+            if kind.is_required() and not mapped_args and not is_unexpected_arg_error:
                 # No actual for a mandatory formal
                 if kind.is_positional():
                     self.msg.too_few_arguments(callee, context, actual_names)
@@ -2368,28 +2369,36 @@ def check_argument_count(
                     self.msg.missing_named_argument(callee, context, argname)
                 ok = False
             elif not kind.is_star() and is_duplicate_mapping(
-                formal_to_actual[i], actual_types, actual_kinds
+                mapped_args, actual_types, actual_kinds
             ):
                 if self.chk.in_checked_function() or isinstance(
-                    get_proper_type(actual_types[formal_to_actual[i][0]]), TupleType
+                    get_proper_type(actual_types[mapped_args[0]]), TupleType
                 ):
                     self.msg.duplicate_argument_value(callee, i, context)
                     ok = False
             elif (
                 kind.is_named()
-                and formal_to_actual[i]
-                and actual_kinds[formal_to_actual[i][0]] not in [nodes.ARG_NAMED, nodes.ARG_STAR2]
+                and mapped_args
+                and actual_kinds[mapped_args[0]] not in [nodes.ARG_NAMED, nodes.ARG_STAR2]
             ):
                 # Positional argument when expecting a keyword argument.
                 self.msg.too_many_positional_arguments(callee, context)
                 ok = False
-            elif (
-                callee.param_spec() is not None
-                and not formal_to_actual[i]
-                and callee.special_sig != "partial"
-            ):
-                self.msg.too_few_arguments(callee, context, actual_names)
-                ok = False
+            elif callee.param_spec() is not None:
+                if not mapped_args and callee.special_sig != "partial":
+                    self.msg.too_few_arguments(callee, context, actual_names)
+                    ok = False
+                elif len(mapped_args) > 1:
+                    paramspec_entries = sum(
+                        isinstance(get_proper_type(actual_types[k]), ParamSpecType)
+                        for k in mapped_args
+                    )
+                    if actual_kinds[mapped_args[0]] == nodes.ARG_STAR and paramspec_entries > 1:
+                        self.msg.fail("ParamSpec.args should only be passed once", context)
+                        ok = False
+                    if actual_kinds[mapped_args[0]] == nodes.ARG_STAR2 and paramspec_entries > 1:
+                        self.msg.fail("ParamSpec.kwargs should only be passed once", context)
+                        ok = False
         return ok
 
     def check_for_extra_actual_arguments(

test-data/unit/check-parameter-specification.test

@@ -2560,3 +2560,46 @@ def fn(f: MiddlewareFactory[P]) -> Capture[P]: ...
 
 reveal_type(fn(ServerErrorMiddleware))  # N: Revealed type is "__main__.Capture[[handler: Union[builtins.str, None] =, debug: builtins.bool =]]"
 [builtins fixtures/paramspec.pyi]
+
+[case testRunParamSpecDuplicateArgsKwargs]
+from typing_extensions import ParamSpec, Concatenate
+from typing import Callable, Union
+
+_P = ParamSpec("_P")
+
+def run(predicate: Callable[_P, None], *args: _P.args, **kwargs: _P.kwargs) -> None:
+    predicate(*args, *args, **kwargs)  # E: ParamSpec.args should only be passed once
+    predicate(*args, **kwargs, **kwargs)  # E: ParamSpec.kwargs should only be passed once
+    predicate(*args, *args, **kwargs, **kwargs)  # E: ParamSpec.args should only be passed once \
+                                                 # E: ParamSpec.kwargs should only be passed once
+    copy_args = args
+    copy_kwargs = kwargs
+    predicate(*args, *copy_args, **kwargs)  # E: ParamSpec.args should only be passed once
+    predicate(*copy_args, *args, **kwargs)  # E: ParamSpec.args should only be passed once
+    predicate(*args, **copy_kwargs, **kwargs)  # E: ParamSpec.kwargs should only be passed once
+    predicate(*args, **kwargs, **copy_kwargs)  # E: ParamSpec.kwargs should only be passed once
+
+def run2(predicate: Callable[Concatenate[int, _P], None], *args: _P.args, **kwargs: _P.kwargs) -> None:
+    predicate(*args, *args, **kwargs)  # E: ParamSpec.args should only be passed once \
+                                       # E: Argument 1 has incompatible type "*_P.args"; expected "int"
+    predicate(*args, **kwargs, **kwargs)  # E: ParamSpec.kwargs should only be passed once \
+                                          # E: Argument 1 has incompatible type "*_P.args"; expected "int"
+    predicate(1, *args, *args, **kwargs)  # E: ParamSpec.args should only be passed once
+    predicate(1, *args, **kwargs, **kwargs)  # E: ParamSpec.kwargs should only be passed once
+    predicate(1, *args, *args, **kwargs, **kwargs)  # E: ParamSpec.args should only be passed once \
+                                                    # E: ParamSpec.kwargs should only be passed once
+    copy_args = args
+    copy_kwargs = kwargs
+    predicate(1, *args, *copy_args, **kwargs)  # E: ParamSpec.args should only be passed once
+    predicate(1, *copy_args, *args, **kwargs)  # E: ParamSpec.args should only be passed once
+    predicate(1, *args, **copy_kwargs, **kwargs)  # E: ParamSpec.kwargs should only be passed once
+    predicate(1, *args, **kwargs, **copy_kwargs)  # E: ParamSpec.kwargs should only be passed once
+
+def run3(predicate: Callable[Concatenate[int, str, _P], None], *args: _P.args, **kwargs: _P.kwargs) -> None:
+    base_ok: tuple[int, str]
+    predicate(*base_ok, *args, **kwargs)
+    base_bad: tuple[Union[int, str], ...]
+    predicate(*base_bad, *args, **kwargs)  # E: Argument 1 has incompatible type "*Tuple[Union[int, str], ...]"; expected "int" \
+                                           # E: Argument 1 has incompatible type "*Tuple[Union[int, str], ...]"; expected "str" \
+                                           # E: Argument 1 has incompatible type "*Tuple[Union[int, str], ...]"; expected "_P.args"
+[builtins fixtures/paramspec.pyi]