stubgen: Fix the detection of modules without spec.

This PR changes the logic of `is_valid_module` used in `simplify_types`.
That function uses `importlib.util.find_spec` and previously tested the
return value for `is None`. However, (1) if the spec is actually `None`,
then the function doesn't return `None` but raises `ValueError`, so that
test never succeeded and (2) if a module with a `None` spec was found,
we have still found a module, so `is_valid_module` should actually
return `True` instead of `False`.

Signed-off-by: Ingo Müller <[email protected]>

Author: ingomueller-net

src/stubgen.py

@@ -649,8 +649,14 @@ def process_ndarray(m: Match[str]) -> str:
         def process_general(m: Match[str]) -> str:
             def is_valid_module(module_name: str) -> bool:
                 try:
-                    return importlib.util.find_spec(module_name) is not None
-                except (ModuleNotFoundError, ValueError):
+                    importlib.util.find_spec(module_name)
+                    # If we get here, the module exists and has a valid spec.
+                    return True
+                except ValueError:
+                    # The module exists but has no spec, `find_spec` raises a
+                    # `ValueError`, so if we get here, the module does exist.
+                    return True
+                except ModuleNotFoundError:
                     return False
 
             full_name, mod_name, cls_name = m.group(0), m.group(1)[:-1], m.group(2)