Caching: Try to import an identifier if it is a class path

Raise a `ValueError` if the identifier cannot be imported, which will
help prevent accidental typos from appearing that the caching
configuration is being ignored.

aiida/manage/caching.py

@@ -175,14 +175,13 @@ def get_use_cache(*, identifier=None):
                     most_specific.append(PatternWithResult(pattern=specific_pattern, use_cache=False))
 
             if len(most_specific) > 1:
-                raise exceptions.ConfigurationError((
-                    'Invalid configuration: multiple matches for identifier {}'
-                    ', but the most specific identifier is not unique. Candidates: {}'
-                ).format(identifier, [match.pattern for match in most_specific]))
+                raise exceptions.ConfigurationError(
+                    f'Invalid configuration: multiple matches for identifier {identifier}'
+                    f', but the most specific identifier is not unique. Candidates: {[match.pattern for match in most_specific]}'
+                )
             if not most_specific:
                 raise exceptions.ConfigurationError(
-                    'Invalid configuration: multiple matches for identifier {}, but none of them is most specific.'.
-                    format(identifier)
+                    f'Invalid configuration: multiple matches for identifier {identifier}, but none of them is most specific.'
                 )
             return most_specific[0].use_cache
         if enable_matches:
@@ -221,6 +220,8 @@ def _validate_identifier_pattern(*, identifier):
     :param identifier: Process type string, or a pattern with '*' wildcard that matches it.
     :type identifier: str
     """
+    import importlib
+
     common_error_msg = f"Invalid identifier pattern '{identifier}': "
     assert ENTRY_POINT_STRING_SEPARATOR not in '.*'  # The logic of this function depends on this
     # Check if it can be an entry point string
@@ -237,13 +238,14 @@ def _validate_identifier_pattern(*, identifier):
             for group_name in ENTRY_POINT_GROUP_TO_MODULE_PATH_MAP
         ):
             raise ValueError(
-                common_error_msg + "Group name pattern '{}' does not match any of the AiiDA entry point group names.".
-                format(group_pattern)
+                common_error_msg +
+                f"Group name pattern '{group_pattern}' does not match any of the AiiDA entry point group names."
             )
         # The group name pattern matches, and there are no further
         # entry point string separators in the identifier, hence it is
         # a valid pattern.
         return
+
     # The separator might be swallowed in a wildcard, for example
     # aiida.* or aiida.calculations*
     if '*' in identifier:
@@ -267,3 +269,14 @@ def _validate_identifier_pattern(*, identifier):
                 raise ValueError(f"{common_error_msg}'{identifier_part}' is not a valid Python identifier.")
             if keyword.iskeyword(identifier_part):
                 raise ValueError(f"{common_error_msg}'{identifier_part}' is a reserved Python keyword.")
+
+    # If there is no separator, it must be a fully qualified Python name.
+    try:
+        module_name = '.'.join(identifier.split('.')[:-1])
+        class_name = identifier.split('.')[-1]
+
+        spec = importlib.util.find_spec(module_name)
+        module = importlib.util.module_from_spec(spec)
+        cls = getattr(module, class_name)
+    except (ModuleNotFoundError, AttributeError) as exc:
+        raise ValueError(common_error_msg + f'{identifier} can not be imported.') from exc

tests/manage/test_caching_config.py

@@ -267,7 +267,7 @@ def test_disable_caching_global(configure_caching):
 @pytest.mark.parametrize(
     'identifier', [
         'aiida.spam:Ni', 'aiida.calculations:With:second_separator', 'aiida.sp*:Ni', 'aiida.sp*!bar',
-        'startswith.number.2bad', 'some.thing.in.this.is.a.keyword'
+        'startswith.number.2bad', 'some.thing.in.this.is.a.keyword', 'invalid_module.AClass'
     ]
 )
 def test_enable_disable_invalid(identifier):