Enable check_untyped_defs and make mypy hook blocking

Fix the 13 errors that surfaced under mypy --check-untyped-defs so the
flag can be turned on permanently in pyproject.toml, and drop the
advisory exit-0 wrapper on the mypy pre-commit hook now that the tree is
clean.

- _plugin_manager: rename colliding loop vars (module/name were reused
  with conflicting types) and guard spec/spec.loader from
  spec_from_file_location; call __init__ via the class in __setstate__.
- __main__: pass Verbosity(options.verbose), not a bare int.
- subprocess/_check: widen package to str | Mapping[str, str] to match
  _error_trailer's existing per-platform handling.
- optimize.main: annotate the standalone PdfContext(..., None, None) that
  only ever reads context.options.

src/ocrmypdf/__main__.py

@@ -49,7 +49,7 @@ def run(args=None):
     with suppress(AttributeError, PermissionError):
         os.nice(5)
 
-    verbosity = options.verbose
+    verbosity = Verbosity(options.verbose)
     if not os.isatty(sys.stderr.fileno()):
         options.progress_bar = False
     if options.quiet:

src/ocrmypdf/_plugin_manager.py

@@ -76,7 +76,8 @@ class OcrmypdfPluginManager:
         return state
 
     def __setstate__(self, state):
-        self.__init__(
+        OcrmypdfPluginManager.__init__(
+            self,
             *state['init_args'],
             plugins=state['plugins'],
             builtins=state['builtins'],
@@ -88,10 +89,10 @@ class OcrmypdfPluginManager:
 
         # 1. Register builtins
         if self._builtins:
-            for module in sorted(
+            for module_info in sorted(
                 pkgutil.iter_modules(ocrmypdf.builtin_plugins.__path__)
             ):
-                name = f'ocrmypdf.builtin_plugins.{module.name}'
+                name = f'ocrmypdf.builtin_plugins.{module_info.name}'
                 module = importlib.import_module(name)
                 self._pm.register(module)
 
@@ -99,17 +100,20 @@ class OcrmypdfPluginManager:
         self._pm.load_setuptools_entrypoints('ocrmypdf')
 
         # 3. Register plugins specified on command line
-        for name in self._plugins:
-            if isinstance(name, Path) or name.endswith('.py'):
+        for plugin in self._plugins:
+            if isinstance(plugin, Path) or plugin.endswith('.py'):
                 # Import by filename
-                module_name = Path(name).stem
-                spec = importlib.util.spec_from_file_location(module_name, name)
+                plugin_path = Path(plugin)
+                module_name = plugin_path.stem
+                spec = importlib.util.spec_from_file_location(module_name, plugin_path)
+                if spec is None or spec.loader is None:
+                    raise ImportError(f'Could not load plugin from {plugin_path}')
                 module = importlib.util.module_from_spec(spec)
                 sys.modules[module_name] = module
                 spec.loader.exec_module(module)
             else:
                 # Import by dotted module name
-                module = importlib.import_module(name)
+                module = importlib.import_module(plugin)
             self._pm.register(module)
 
     # =========================================================================

src/ocrmypdf/optimize.py

@@ -774,7 +774,9 @@ def main(infile, outfile, level, jobs=1):
     )
 
     with TemporaryDirectory() as tmpdir:
-        context = PdfContext(options, Path(tmpdir), infile, None, None)
+        # optimize() only reads context.options on this standalone path, so
+        # pdfinfo and plugin_manager are not needed.
+        context = PdfContext(options, Path(tmpdir), infile, None, None)  # type: ignore[arg-type]
         tmpout = Path(tmpdir) / 'out.pdf'
         optimize(
             infile,

src/ocrmypdf/subprocess/_check.py

@@ -94,7 +94,10 @@ def _error_trailer(program: str, package: str | Mapping[str, str], **kwargs) ->
 
 
 def _error_missing_program(
-    program: str, package: str, required_for: str | None, recommended: bool
+    program: str,
+    package: str | Mapping[str, str],
+    required_for: str | None,
+    recommended: bool,
 ) -> None:
     # pylint: disable=unused-argument
     if recommended:
@@ -108,7 +111,7 @@ def _error_missing_program(
 
 def _error_old_version(
     program: str,
-    package: str,
+    package: str | Mapping[str, str],
     need_version: str,
     found_version: str,
     required_for: str | None,
@@ -124,7 +127,7 @@ def _error_old_version(
 def check_external_program(
     *,
     program: str,
-    package: str,
+    package: str | Mapping[str, str],
     version_checker: Callable[[], Version],
     need_version: str | Version,
     required_for: str | None = None,