feat: Allow loading extension from file path

src/griffe/agents/extensions/base.py

@@ -3,7 +3,10 @@
 from __future__ import annotations
 
 import enum
+import os
+import sys
 from collections import defaultdict
+from importlib.util import module_from_spec, spec_from_file_location
 from inspect import isclass
 from typing import TYPE_CHECKING, Any, Sequence, Union
 
@@ -13,6 +16,7 @@
 
 if TYPE_CHECKING:
     import ast
+    from types import ModuleType
 
     from griffe.agents.inspector import Inspector
     from griffe.agents.nodes import ObjectNode
@@ -223,6 +227,17 @@ def after_inspection(self) -> list[InspectorExtension]:
 }
 
 
+def _load_extension_path(path: str) -> ModuleType:
+    module_name = os.path.basename(path).rsplit(".", 1)[0]
+    spec = spec_from_file_location(module_name, path)
+    if not spec:
+        raise ExtensionNotLoadedError(f"Could not import module from path '{path}'")
+    module = module_from_spec(spec)
+    sys.modules[module_name] = module
+    spec.loader.exec_module(module)  # type: ignore[union-attr]
+    return module
+
+
 def load_extension(extension: str | dict[str, Any] | Extension | type[Extension]) -> Extension:
     """Load a configured extension.
 
@@ -238,6 +253,8 @@ def load_extension(extension: str | dict[str, Any] | Extension | type[Extension]
     Returns:
         An extension instance.
     """
+    ext_object = None
+
     if isinstance(extension, (VisitorExtension, InspectorExtension)):
         return extension
 
@@ -253,16 +270,25 @@ def load_extension(extension: str | dict[str, Any] | Extension | type[Extension]
 
     if import_path in builtin_extensions:
         import_path = f"griffe.agents.extensions.{import_path}"
+    elif os.path.exists(import_path):
+        try:
+            ext_object = _load_extension_path(import_path)
+        except ImportError as error:
+            raise ExtensionNotLoadedError(f"Extension module '{import_path}' could not be found") from error
+
+    if not ext_object:
+        try:
+            ext_object = dynamic_import(import_path)
+        except ModuleNotFoundError as error:
+            raise ExtensionNotLoadedError(f"Extension module '{import_path}' could not be found") from error
+        except ImportError as error:
+            raise ExtensionNotLoadedError(f"Error while importing extension '{import_path}': {error}") from error
+
+    if isclass(ext_object) and issubclass(ext_object, (VisitorExtension, InspectorExtension)):
+        return ext_object(**options)  # type: ignore[misc]
 
     try:
-        ext_module = dynamic_import(import_path)
-    except ModuleNotFoundError as error:
-        raise ExtensionNotLoadedError(f"Extension module '{import_path}' could not be found") from error
-    except ImportError as error:
-        raise ExtensionNotLoadedError(f"Error while importing extension module '{import_path}': {error}") from error
-
-    try:
-        return ext_module.Extension(**options)
+        return ext_object.Extension(**options)  # type: ignore[union-attr]
     except AttributeError as error:
         raise ExtensionNotLoadedError(f"Extension module '{import_path}' has no 'Extension' attribute") from error