Let AstroidManager.clear_cache reload brain plugins

ChangeLog

@@ -13,6 +13,8 @@ Release date: TBA
 
   Closes #1512
 
+* Allowed ``AstroidManager.clear_cache`` to reload necessary brain plugins.
+
 * Rename ``ModuleSpec`` -> ``module_type`` constructor parameter to match attribute
   name and improve typing. Use ``type`` instead.
 

astroid/__init__.py

@@ -33,7 +33,6 @@
 import functools
 import tokenize
 from importlib import import_module
-from pathlib import Path
 
 # isort: off
 # We have an isort: off on '__version__' because the packaging need to access
@@ -49,7 +48,7 @@
 from astroid.bases import BaseInstance, BoundMethod, Instance, UnboundMethod
 from astroid.brain.helpers import register_module_extender
 from astroid.builder import extract_node, parse
-from astroid.const import PY310_PLUS, Context, Del, Load, Store
+from astroid.const import BRAIN_MODULES_DIRECTORY, PY310_PLUS, Context, Del, Load, Store
 from astroid.exceptions import (
     AstroidBuildingError,
     AstroidBuildingException,
@@ -193,8 +192,6 @@
     tokenize._compile = functools.lru_cache()(tokenize._compile)  # type: ignore[attr-defined]
 
 # load brain plugins
-ASTROID_INSTALL_DIRECTORY = Path(__file__).parent
-BRAIN_MODULES_DIRECTORY = ASTROID_INSTALL_DIRECTORY / "brain"
 for module in BRAIN_MODULES_DIRECTORY.iterdir():
     if module.suffix == ".py":
         import_module(f"astroid.brain.{module.stem}")

astroid/const.py

@@ -4,6 +4,7 @@
 
 import enum
 import sys
+from pathlib import Path
 
 PY36 = sys.version_info[:2] == (3, 6)
 PY38 = sys.version_info[:2] == (3, 8)
@@ -30,3 +31,7 @@ class Context(enum.Enum):
 Load = Context.Load
 Store = Context.Store
 Del = Context.Del
+
+
+ASTROID_INSTALL_DIRECTORY = Path(__file__).parent
+BRAIN_MODULES_DIRECTORY = ASTROID_INSTALL_DIRECTORY / "brain"

astroid/manager.py

@@ -10,8 +10,10 @@
 import os
 import types
 import zipimport
+from importlib.util import find_spec, module_from_spec
 from typing import TYPE_CHECKING, ClassVar, List, Optional
 
+from astroid.const import BRAIN_MODULES_DIRECTORY
 from astroid.exceptions import AstroidBuildingError, AstroidImportError
 from astroid.interpreter._import import spec
 from astroid.modutils import (
@@ -360,7 +362,16 @@ def bootstrap(self):
 
         raw_building._astroid_bootstrapping()
 
-    def clear_cache(self):
-        """Clear the underlying cache. Also bootstraps the builtins module."""
+    def clear_cache(self) -> None:
+        """Clear the underlying cache, bootstrap the builtins module and
+        re-register transforms."""
         self.astroid_cache.clear()
+        AstroidManager.brain["_transform"] = TransformVisitor()
         self.bootstrap()
+
+        # Reload brain plugins. During initialisation this is done in astroid.__init__.py
+        for module in BRAIN_MODULES_DIRECTORY.iterdir():
+            if module.suffix == ".py":
+                module_spec = find_spec(f"astroid.brain.{module.stem}")
+                module_object = module_from_spec(module_spec)
+                module_spec.loader.exec_module(module_object)

tests/resources.py

@@ -36,13 +36,13 @@ def tearDown(self) -> None:
 
 
 class AstroidCacheSetupMixin:
-    """Mixin for handling the astroid cache problems.
+    """Mixin for handling test isolation issues with the astroid cache.
 
-    When clearing the astroid cache, some tests fails due to
+    When clearing the astroid cache, some tests fail due to
     cache inconsistencies, where some objects had a different
     builtins object referenced.
-    This saves the builtins module and makes sure to add it
-    back to the astroid_cache after the tests finishes.
+    This saves the builtins module and TransformVisitor and
+    replaces them after the tests finish.
     The builtins module is special, since some of the
     transforms for a couple of its objects (str, bytes etc)
     are executed only once, so astroid_bootstrapping will be
@@ -52,8 +52,9 @@ class AstroidCacheSetupMixin:
     @classmethod
     def setup_class(cls):
         cls._builtins = AstroidManager().astroid_cache.get("builtins")
+        cls._transforms = AstroidManager.brain["_transform"]
 
     @classmethod
     def teardown_class(cls):
-        if cls._builtins:
-            AstroidManager().astroid_cache["builtins"] = cls._builtins
+        AstroidManager().astroid_cache["builtins"] = cls._builtins
+        AstroidManager.brain["_transform"] = cls._transforms

tests/unittest_manager.py

@@ -16,6 +16,7 @@
 from astroid import manager, test_utils
 from astroid.const import IS_JYTHON
 from astroid.exceptions import AstroidBuildingError, AstroidImportError
+from astroid.nodes import Const
 
 from . import resources
 
@@ -315,5 +316,13 @@ def test_borg(self) -> None:
         self.assertIs(built, second_built)
 
 
+class ClearCacheTest(unittest.TestCase, resources.AstroidCacheSetupMixin):
+    def test_brain_plugins_reloaded_after_clearing_cache(self) -> None:
+        astroid.MANAGER.clear_cache()
+        format_call = astroid.extract_node("''.format()")
+        inferred = next(format_call.infer())
+        self.assertIsInstance(inferred, Const)
+
+
 if __name__ == "__main__":
     unittest.main()