Upgrade to latest mypy (#853)

.pre-commit-config.yaml

@@ -8,7 +8,7 @@ repos:
       - id: trailing-whitespace
 
   - repo: https://github.com/pre-commit/mirrors-mypy
-    rev: v0.991
+    rev: v1.13.0
     hooks:
       - id: mypy
         exclude: '^(docs|tasks|tests)|setup\.py'

pyproject.toml

@@ -52,6 +52,7 @@ strict = true
 show_error_codes = true
 enable_error_code = ["ignore-without-code", "redundant-expr", "truthy-bool"]
 warn_unused_ignores = true
+python_version = 3.8
 
 [[tool.mypy.overrides]]
 module = ["_manylinux"]

src/packaging/metadata.py

@@ -1,12 +1,12 @@
 from __future__ import annotations
 
-import builtins
 import email.feedparser
 import email.header
 import email.message
 import email.parser
 import email.policy
 import pathlib
+import sys
 import typing
 from typing import (
     Any,
@@ -24,7 +24,7 @@
 T = typing.TypeVar("T")
 
 
-if "ExceptionGroup" in builtins.__dict__:  # pragma: no cover
+if sys.version_info >= (3, 11):  # pragma: no cover
     ExceptionGroup = ExceptionGroup
 else:  # pragma: no cover
 
@@ -222,12 +222,14 @@ def _get_payload(msg: email.message.Message, source: bytes | str) -> str:
     # If our source is a str, then our caller has managed encodings for us,
     # and we don't need to deal with it.
     if isinstance(source, str):
-        payload: str = msg.get_payload()
+        payload = msg.get_payload()
+        assert isinstance(payload, str)
         return payload
     # If our source is a bytes, then we're managing the encoding and we need
     # to deal with it.
     else:
-        bpayload: bytes = msg.get_payload(decode=True)
+        bpayload = msg.get_payload(decode=True)
+        assert isinstance(bpayload, bytes)
         try:
             return bpayload.decode("utf8", "strict")
         except UnicodeDecodeError as exc:
@@ -434,7 +436,7 @@ def parse_email(data: bytes | str) -> tuple[RawMetadata, dict[str, list[str]]]:
         payload = _get_payload(parsed, data)
     except ValueError:
         unparsed.setdefault("description", []).append(
-            parsed.get_payload(decode=isinstance(data, bytes))
+            parsed.get_payload(decode=isinstance(data, bytes))  # type: ignore[call-overload]
         )
     else:
         if payload:

src/packaging/tags.py

@@ -490,7 +490,7 @@ def ios_platforms(
         # if iOS is the current platform, ios_ver *must* be defined. However,
         # it won't exist for CPython versions before 3.13, which causes a mypy
         # error.
-        _, release, _, _ = platform.ios_ver()  # type: ignore[attr-defined]
+        _, release, _, _ = platform.ios_ver()  # type: ignore[attr-defined, unused-ignore]
         version = cast("AppleVersion", tuple(map(int, release.split(".")[:2])))
 
     if multiarch is None:

src/packaging/version.py

@@ -493,7 +493,9 @@ def _parse_letter_version(
             letter = "post"
 
         return letter, int(number)
-    if not letter and number:
+
+    assert not letter
+    if number:
         # We assume if we are given a number, but we are not given a letter
         # then this is using the implicit post release syntax (e.g. 1.0-1)
         letter = "post"