gh-108455: Run mypy on Tools/peg_generator

.github/workflows/mypy.yml

@@ -28,7 +28,11 @@ jobs:
   mypy:
     strategy:
       matrix:
-        target: ["Tools/cases_generator", "Tools/clinic"]
+        target: [
+          "Tools/cases_generator",
+          "Tools/clinic",
+          "Tools/peg_generator",
+        ]
     name: Run mypy on ${{ matrix.target }}
     runs-on: ubuntu-latest
     timeout-minutes: 10

Tools/peg_generator/mypy.ini

@@ -1,5 +1,6 @@
 [mypy]
-files = pegen
+files = Tools/peg_generator/pegen
+pretty = True
 
 follow_imports = error
 no_implicit_optional = True

Tools/peg_generator/pegen/build.py

@@ -5,7 +5,7 @@
 import sysconfig
 import tempfile
 import tokenize
-from typing import IO, Dict, List, Optional, Set, Tuple
+from typing import IO, Any, Dict, List, Optional, Set, Tuple
 
 from pegen.c_generator import CParserGenerator
 from pegen.grammar import Grammar
@@ -18,6 +18,7 @@
 MOD_DIR = pathlib.Path(__file__).resolve().parent
 
 TokenDefinitions = Tuple[Dict[int, str], Dict[str, int], Set[str]]
+Incomplete = Any  # TODO: install `types-setuptools` and remove this alias
 
 
 def get_extra_flags(compiler_flags: str, compiler_py_flags_nodist: str) -> List[str]:
@@ -28,7 +29,7 @@ def get_extra_flags(compiler_flags: str, compiler_py_flags_nodist: str) -> List[
     return f"{flags} {py_flags_nodist}".split()
 
 
-def fixup_build_ext(cmd):
+def fixup_build_ext(cmd: Incomplete) -> None:
     """Function needed to make build_ext tests pass.
 
     When Python was built with --enable-shared on Unix, -L. is not enough to
@@ -74,7 +75,7 @@ def compile_c_extension(
     keep_asserts: bool = True,
     disable_optimization: bool = False,
     library_dir: Optional[str] = None,
-) -> str:
+) -> pathlib.Path:
     """Compile the generated source for a parser generator into an extension module.
 
     The extension module will be generated in the same directory as the provided path
@@ -89,12 +90,12 @@ def compile_c_extension(
     static library of the common parser sources (this is useful in case you are
     creating multiple extensions).
     """
-    import setuptools.logging
+    import setuptools.logging  # type: ignore[import]
 
     from setuptools import Extension, Distribution
-    from setuptools._distutils.dep_util import newer_group
-    from setuptools._distutils.ccompiler import new_compiler
-    from setuptools._distutils.sysconfig import customize_compiler
+    from setuptools._distutils.dep_util import newer_group  # type: ignore[import]
+    from setuptools._distutils.ccompiler import new_compiler  # type: ignore[import]
+    from setuptools._distutils.sysconfig import customize_compiler  # type: ignore[import]
 
     if verbose:
         setuptools.logging.set_threshold(setuptools.logging.logging.DEBUG)

Tools/peg_generator/pegen/parser.py

@@ -21,7 +21,7 @@ def logger(method: F) -> F:
     """
     method_name = method.__name__
 
-    def logger_wrapper(self: P, *args: object) -> T:
+    def logger_wrapper(self: P, *args: object) -> Any:
         if not self._verbose:
             return method(self, *args)
         argsr = ",".join(repr(arg) for arg in args)
@@ -41,7 +41,7 @@ def memoize(method: F) -> F:
     """Memoize a symbol method."""
     method_name = method.__name__
 
-    def memoize_wrapper(self: P, *args: object) -> T:
+    def memoize_wrapper(self: P, *args: object) -> Any:
         mark = self._mark()
         key = mark, method_name, args
         # Fast path: cache hit, and not verbose.

Tools/requirements-dev.txt

@@ -1,3 +1,3 @@
 # Requirements file for external linters and checks we run on
-# Tools/clinic and Tools/cases_generator/ in CI
+# Tools/clinic, Tools/cases_generator/, and Tools/peg_generator/ in CI
 mypy==1.5.1