Wiped get_commands() cache when INSTALLED_APPS changes.

Refs #21018, #21688.

2 files changed, 28 insertions, 29 deletions

diff --git a/django/core/management/__init__.py b/django/core/management/__init__.py
index 3d6482f236..1b9597ee3d 100644
--- a/django/core/management/__init__.py
+++ b/django/core/management/__init__.py
@@ -11,15 +11,12 @@ from django.conf import settings
 from django.core.exceptions import ImproperlyConfigured
 from django.core.management.base import BaseCommand, CommandError, handle_default_options
 from django.core.management.color import color_style
+from django.utils import lru_cache
 from django.utils import six
 
 # For backwards compatibility: get_version() used to be in this module.
 from django import get_version
 
-# A cache of loaded commands, so that call_command
-# doesn't have to reload every time it's called.
-_commands = None
-
 
 def find_commands(management_dir):
     """
@@ -85,6 +82,7 @@ def load_command_class(app_name, name):
     return module.Command()
 
 
+@lru_cache.lru_cache(maxsize=None)
 def get_commands():
     """
     Returns a dictionary mapping command names to their callback applications.
@@ -107,34 +105,32 @@ def get_commands():
     The dictionary is cached on the first call and reused on subsequent
     calls.
     """
-    global _commands
-    if _commands is None:
-        _commands = dict((name, 'django.core') for name in find_commands(__path__[0]))
+    commands = {name: 'django.core' for name in find_commands(__path__[0])}
 
-        # Find the installed apps
-        try:
-            settings.INSTALLED_APPS
-        except ImproperlyConfigured:
-            # Still useful for commands that do not require functional
-            # settings, like startproject or help.
-            app_names = []
-        else:
-            # Setup Django outside of the try/except block to avoid catching
-            # ImproperlyConfigured errors that aren't caused by the absence of
-            # a settings module.
-            django.setup()
-            app_configs = apps.get_app_configs()
-            app_names = [app_config.name for app_config in app_configs]
+    # Find the installed apps
+    try:
+        settings.INSTALLED_APPS
+    except ImproperlyConfigured:
+        # Still useful for commands that do not require functional
+        # settings, like startproject or help.
+        app_names = []
+    else:
+        # Setup Django outside of the try/except block to avoid catching
+        # ImproperlyConfigured errors that aren't caused by the absence of
+        # a settings module.
+        django.setup()
+        app_configs = apps.get_app_configs()
+        app_names = [app_config.name for app_config in app_configs]
 
-        # Find and load the management module for each installed app.
-        for app_name in app_names:
-            try:
-                path = find_management_module(app_name)
-                _commands.update(dict((name, app_name) for name in find_commands(path)))
-            except ImportError:
-                pass  # No management module - ignore this app
+    # Find and load the management module for each installed app.
+    for app_name in app_names:
+        try:
+            path = find_management_module(app_name)
+            commands.update({name: app_name for name in find_commands(path)})
+        except ImportError:
+            pass  # No management module - ignore this app
 
-    return _commands
+    return commands
 
 
 def call_command(name, *args, **options):
diff --git a/django/test/signals.py b/django/test/signals.py
index b806592919..d5b98081b9 100644
--- a/django/test/signals.py
+++ b/django/test/signals.py
@@ -39,6 +39,9 @@ def update_installed_apps(**kwargs):
         # Rebuild templatetags module cache.
         from django.template import base
         base.templatetags_modules[:] = []
+        # Rebuild management commands cache
+        from django.core.management import get_commands
+        get_commands.cache_clear()
 
 
 @receiver(setting_changed)