Fix ParamSpec bugs that are blocking typeshed.

rchen152 · rchen152 · commit 76a2ea1aa261 · 2022-01-03T20:04:24.000-08:00
* Don't create multiple TypeVars for the same ParamSpec. We were creating a new TypeVar every time we saw a ParamSpec used in a class definition, leading to "Duplicate top-level identifier" errors. * Show a more helpful error message when P.args or P.kwargs is misspelled. Misspelling a ParamSpec attribute previously produced a mysterious "Can't find pyi for <ParamSpec name>" error at the dependency loading phase. See python/typeshed#6670 and python/typeshed#6676. PiperOrigin-RevId: 419457152
diff --git a/pytype/pyi/definitions.py b/pytype/pyi/definitions.py
@@ -2,7 +2,6 @@
 
 import collections
 import dataclasses
-import re
 import sys
 
 from typing import Any, Dict, List, Optional, Union
@@ -529,7 +528,8 @@ def _parameterized_type(self, base_type: Any, parameters):
               self._matches_full_name(base_type, "typing.Generic")):
           # Replacing a ParamSpec with a TypeVar isn't correct, but it'll work
           # for simple cases in which the filled value is also a ParamSpec.
-          self.type_params.append(pytd.TypeParameter(p.name))
+          if not any(t.name == p.name for t in self.type_params):
+            self.type_params.append(pytd.TypeParameter(p.name))
           processed = p
         elif (p in self.param_specs or
               (isinstance(p, pytd.GenericType) and
@@ -590,7 +590,10 @@ def new_type(
     """
     base_type = self.resolve_type(name)
     for p in self.param_specs:
-      if re.fullmatch(rf"{p.name}\.(args|kwargs)", base_type.name):
+      if base_type.name.startswith(f"{p.name}."):
+        _, attr = base_type.name.split(".", 1)
+        if attr not in ("args", "kwargs"):
+          raise ParseError(f"Unrecognized ParamSpec attribute: {attr}")
         # We do not yet support typing.ParamSpec, so replace references to its
         # args and kwargs attributes with Any.
         return pytd.AnythingType()
diff --git a/pytype/pyi/parser_test.py b/pytype/pyi/parser_test.py
@@ -2889,6 +2889,34 @@ def f(x: Callable[P, T], *args: P.args, **kwargs: P.kwargs) -> T: ...
       def f(x: Callable[..., T], *args, **kwargs) -> T: ...
     """)
 
+  def test_paramspec_args_error(self):
+    self.check_error("""
+      from typing import Any, Callable
+      from typing_extensions import ParamSpec
+      _P = ParamSpec("_P")
+
+      class Foo:
+        def __init__(
+            self, func: Callable[_P, Any], args: _P.args, kwds: _P.kwds
+        ) -> None: ...
+    """, 7, "Unrecognized ParamSpec attribute: kwds")
+
+  def test_two_classes(self):
+    self.check("""
+      from typing import Generic, ParamSpec
+      P = ParamSpec('P')
+      class C1(Generic[P]): ...
+      class C2(Generic[P]): ...
+    """, """
+      from typing import Generic, TypeVar
+
+      P = TypeVar('P')
+
+      class C1(Generic[P]): ...
+
+      class C2(Generic[P]): ...
+    """)
+
 
 class ConcatenateTest(parser_test_base.ParserTestBase):
 
