Enable TypeAlias check by default

CHANGELOG.rst

@@ -15,7 +15,7 @@ unreleased
   statements). The previous checks were disabled by default.
 * detect usage of non-integer indices in sys.version_info checks
 * extend Y010 to check async functions in addition to normal functions 
-* introduce Y093 (require using TypeAlias for type aliases)
+* introduce Y026 (require using TypeAlias for type aliases)
 * introduce Y017 (disallows assignments with multiple targets or non-name targets)
 * extend Y001 to cover ParamSpec and TypeVarTuple in addition to TypeVar
 * introduce Y018 (detect unused TypeVars)
@@ -28,6 +28,7 @@ unreleased
 * introduce Y023 (prefer ``typing`` over ``typing_extensions``)
 * introduce Y024 (prefer ``typing.NamedTuple`` to ``collections.namedtuple``)
 * introduce Y025 (always alias ``collections.abc.Set``)
+* all errors are now enabled by default
 
 20.10.0
 ~~~~~~~

README.rst

@@ -91,12 +91,16 @@ currently emitted:
   for more precise type inference.
 * Y025: Always alias ``collections.abc.Set`` when importing it, so as to avoid
   confusion with ``builtins.set``.
+* Y026: Type aliases should be explicitly demarcated with ``typing.TypeAlias``.
 * Y028: Always use class-based syntax for ``typing.NamedTuple``, instead of
   assignment-based syntax.
 
-The following warnings are disabled by default:
+Many error codes enforce modern conventions, and some cannot yet be used in
+all cases:
 
-* Y093: Type aliases should be explicitly demarcated with ``typing.TypeAlias``.
+* Y026 is incompatible with the pytype type checker and should be turned
+  off for stubs that need to be compatible with pytype. A fix is tracked
+  `here <https://github.com/google/pytype/issues/787>`_.
 
 License
 -------

pyi.py

@@ -346,14 +346,15 @@ def visit_Assign(self, node: ast.Assign) -> None:
                     self.typevarlike_defs[target_info] = node
                 else:
                     self.error(target, Y001.format(cls_name))
-            # We avoid triggering Y093 in this case because there are various
-            # unusual cases where assignment to the result of a call is legitimate
-            # in stubs.
-            return
         if isinstance(node.value, (ast.Num, ast.Str, ast.Bytes)):
             self.error(node.value, Y015)
-        else:
-            self.error(node, Y093)
+        # We avoid triggering Y026 for calls and = ... because there are various
+        # unusual cases where assignment to the result of a call is legitimate
+        # in stubs.
+        elif target_name != "__all__" and not isinstance(
+            node.value, (ast.Ellipsis, ast.Call)
+        ):
+            self.error(node, Y026)
 
     def visit_Name(self, node: ast.Name) -> None:
         self.all_name_occurrences[node.id] += 1
@@ -803,8 +804,7 @@ def run(self):
         if path.suffix == ".pyi":
             visitor = PyiVisitor(filename=path)
             for error in visitor.run(self.tree):
-                if self.should_warn(error.message[:4]):
-                    yield error
+                yield error
 
     @classmethod
     def add_options(cls, parser):
@@ -830,36 +830,13 @@ def add_options(cls, parser):
         except optparse.OptionConflictError:
             # In tests, sometimes this option gets called twice for some reason.
             pass
-        parser.extend_default_ignore(DISABLED_BY_DEFAULT)
 
     @classmethod
     def parse_options(cls, optmanager, options, extra_args):
         """This is also brittle, only checked with flake8 3.2.1 and master."""
         if not options.no_pyi_aware_file_checker:
             checker.FileChecker = PyiAwareFileChecker
 
-    # Functionality to ignore some warnings. Adapted from flake8-bugbear.
-    def should_warn(self, code):
-        """Returns `True` if flake8-pyi should emit a particular warning.
-        flake8 overrides default ignores when the user specifies
-        `ignore = ` in configuration.  This is problematic because it means
-        specifying anything in `ignore = ` implicitly enables all optional
-        warnings.  This function is a workaround for this behavior.
-        Users should explicitly enable these warnings.
-        """
-        if code[:3] != "Y09":
-            # Normal warnings are safe for emission.
-            return True
-
-        if self.options is None:
-            return True
-
-        for i in range(2, len(code) + 1):
-            if code[:i] in self.options.select:
-                return True
-
-        return False
-
 
 # Please keep error code lists in README and CHANGELOG up to date
 Y001 = "Y001 Name of private {} must start with _"
@@ -892,7 +869,5 @@ def should_warn(self, code):
     'Y025 Use "from collections.abc import Set as AbstractSet" '
     'to avoid confusion with "builtins.set"'
 )
+Y026 = "Y026 Use typing_extensions.TypeAlias for type aliases"
 Y028 = "Y028 Use class-based syntax for NamedTuples"
-Y093 = "Y093 Use typing_extensions.TypeAlias for type aliases"
-
-DISABLED_BY_DEFAULT = [Y093]

tests/aliases.pyi

@@ -1,7 +1,6 @@
-# flags: --select=Y017,Y093
 from typing import TypeAlias, ParamSpec as _ParamSpec, _Alias, TypedDict
 
-X = int  # Y093 Use typing_extensions.TypeAlias for type aliases
+X = int  # Y026 Use typing_extensions.TypeAlias for type aliases
 X: TypeAlias = int
 
 a = b = int  # Y017 Only simple assignments allowed

tests/del.pyi

@@ -1,8 +1,8 @@
-from typing import Union
+from typing import Union, TypeAlias
 
 
-ManyStr = list[EitherStr]
-EitherStr = Union[str, bytes]
+ManyStr: TypeAlias = list[EitherStr]
+EitherStr: TypeAlias = Union[str, bytes]
 
 
 def function(accepts: EitherStr) -> None:

tests/forward_refs.pyi

@@ -1,8 +1,8 @@
-from typing import Optional, Union
+from typing import Optional, Union, TypeAlias
 
 
-MaybeCStr = Optional[CStr]
-CStr = Union[C, str]
+MaybeCStr: TypeAlias = Optional[CStr]
+CStr: TypeAlias = Union[C, str]
 __version__ = ...  # type: str
 __author__ = ...  # type: str
 
@@ -12,14 +12,14 @@ def make_default_c() -> C:
 
 
 class D(C):
-    parent = None  # type: C
+    parent: C
 
     def __init__(self) -> None:
         ...
 
 
 class C:
-    other = None  # type: C
+    other: C
 
     def __init__(self) -> None:
         ...

tests/forward_refs_annassign.pyi

@@ -1,8 +1,8 @@
-from typing import Optional, Union
+from typing import Optional, Union, TypeAlias
 
 
-MaybeCStr = Optional[CStr]
-CStr = Union[C, str]
+MaybeCStr: TypeAlias = Optional[CStr]
+CStr: TypeAlias = Union[C, str]
 __version__: str
 __author__: str
 

tests/quotes.pyi

@@ -1,4 +1,4 @@
-from typing import TypeVar, Literal, Annotated
+from typing import TypeVar, Literal, Annotated, TypeAlias
 
 __all__ = ["f", "g"]
 
@@ -22,7 +22,7 @@ def j() -> "int":  # Y020 Quoted annotations should never be used in stubs
     ...
 
 
-Alias = list["int"]  # Y020 Quoted annotations should never be used in stubs
+Alias: TypeAlias = list["int"]  # Y020 Quoted annotations should never be used in stubs
 
 class Child(list["int"]):  # Y020 Quoted annotations should never be used in stubs
     """Documented and guaranteed useful."""  # Y021 Docstrings should not be included in stubs

tests/vanilla_flake8_not_clean_forward_refs.pyi

@@ -1,9 +1,9 @@
 # flags: --no-pyi-aware-file-checker
-from typing import Union
+from typing import Union, TypeAlias
 
 
-ManyStr = list[EitherStr]  # F821 undefined name 'EitherStr'
-EitherStr = Union[str, bytes]
+ManyStr: TypeAlias = list[EitherStr]  # F821 undefined name 'EitherStr'
+EitherStr: TypeAlias = Union[str, bytes]
 
 
 def function(accepts: EitherStr) -> None: