Disable F821 and F822 by default

CHANGELOG.md

@@ -18,6 +18,11 @@ Features:
 * introduce Y034 (detect common errors where return types are hardcoded, but they
   should use `TypeVar`s instead).
 * introduce Y035 (`__all__` in a stub has the same semantics as at runtime).
+* the plugin now blocks all F821 errors from being reported by
+  flake8/pyflakes. This check does not make sense for `.pyi` files, where names are
+  considered defined if they are annotated, even if they are not actually assigned to.
+  The plugin also now patches flake8 so that it reports F822 in fewer situations, for
+  similar reasons.
 
 ## 22.1.0
 

pyi.py

@@ -18,8 +18,9 @@
 from pathlib import Path
 from typing import TYPE_CHECKING, ClassVar, NamedTuple
 
-from flake8 import checker  # type: ignore
-from flake8.plugins.pyflakes import FlakesChecker  # type: ignore
+from flake8 import checker  # type: ignore[import]
+from flake8.plugins.pyflakes import FlakesChecker  # type: ignore[import]
+from pyflakes import messages  # type: ignore[import]
 from pyflakes.checker import (  # type: ignore[import]
     PY2,
     ClassDefinition,
@@ -149,21 +150,16 @@ def ANNASSIGN(self, node) -> None:
         version, we defer evaluation of the annotations (and values on
         module level).
         """
-        if node.value:
-            # Only bind the *target* if the assignment has value.
-            # Otherwise it's not really ast.Store and shouldn't silence
-            # UndefinedLocal warnings.
-            self.handleNode(node.target, node)
+        self.handleNode(node.target, node)
         if not isinstance(self.scope, FunctionScope):
             self.deferHandleNode(node.annotation, node)
-        if node.value:
-            # If the assignment has value, handle the *value*...
-            if isinstance(self.scope, ModuleScope):
-                # ...later (if module scope).
-                self.deferHandleNode(node.value, node)
-            else:
-                # ...now.
-                self.handleNode(node.value, node)
+        # Handle the *value*...
+        if isinstance(self.scope, ModuleScope):
+            # ...later (if module scope).
+            self.deferHandleNode(node.value, node)
+        else:
+            # ...now.
+            self.handleNode(node.value, node)
 
     def LAMBDA(self, node) -> None:
         """This is likely very brittle, currently works for pyflakes 1.3.0.
@@ -213,6 +209,16 @@ def handleNodeDelete(self, node) -> None:
         """
         return
 
+    def report(self, messageClass, *args, **kwargs) -> None:
+        """Block pyflakes/flake8 from reporting undefined-name errors (F821).
+
+        F821 doesn't doesn't work well in stub files,
+        where names should be considered "defined" if they are annotated,
+        even if they are not assigned to a value.
+        """
+        if messageClass is not messages.UndefinedName:
+            super().report(messageClass, *args, **kwargs)
+
 
 class PyiAwareFileChecker(checker.FileChecker):
     def run_check(self, plugin, **kwargs):

tests/__all__.pyi

@@ -2,6 +2,6 @@ __all__: list[str]  # Y035 "__all__" in a stub file must have a value, as it has
 __all__: list[str] = ["foo", "bar", "baz"]
 __all__ = ["foo", "bar", "baz"]
 
-foo: int = ...
-bar: str = ...
-baz: list[set[bytes]] = ...
+foo: int
+bar: str
+baz: list[set[bytes]]

tests/definitions.pyi

@@ -0,0 +1,12 @@
+from typing import TypeAlias
+
+class _SpecialForm: ...
+
+Protocol: _SpecialForm
+class MyProtocol(Protocol): ...
+
+class WorkingSet:
+    def require(self) -> None: ...
+
+working_set: WorkingSet
+require: TypeAlias = working_set.require

tests/forward_refs.pyi

@@ -2,8 +2,8 @@ from typing import Optional, TypeAlias, Union
 
 MaybeCStr: TypeAlias = Optional[CStr]
 CStr: TypeAlias = Union[C, str]
-__version__: str = ...
-__author__: str = ...
+__version__: str
+__author__: str
 
 def make_default_c() -> C: ...