Context modifiers: Search for context_modifiers.py in registered Django apps

pattern_library/cm_utils.py

@@ -1,7 +1,30 @@
 
 import inspect
+from importlib import import_module
 from typing import Callable
 
+from django.apps import apps
+from django.utils.module_loading import module_has_submodule
+
+
+def get_app_modules():
+    """
+    Generator function that yields a module object for each installed app
+    yields tuples of (app_name, module)
+    """
+    for app in apps.get_app_configs():
+        yield app.name, app.module
+
+
+def get_app_submodules(submodule_name):
+    """
+    Searches each app module for the specified submodule
+    yields tuples of (app_name, module)
+    """
+    for name, module in get_app_modules():
+        if module_has_submodule(module, submodule_name):
+            yield name, import_module('%s.%s' % (name, submodule_name))
+
 
 def accepts_kwarg(func: Callable, kwarg: str) -> bool:
     """

pattern_library/context_modifiers.py

@@ -4,7 +4,7 @@
 
 from django.core.exceptions import ImproperlyConfigured
 
-from .cm_utils import accepts_kwarg
+from .cm_utils import accepts_kwarg, get_app_submodules
 
 GENERIC_CM_KEY = "__generic__"
 ORDER_ATTR_NAME = "__cm_order"
@@ -18,6 +18,12 @@
 class ContextModifierRegistry(defaultdict):
     def __init__(self):
         super().__init__(list)
+        self.searched_for_modifiers = False
+
+    def search_for_modifiers(self) -> None:
+        if not self.searched_for_modifiers:
+            list(get_app_submodules('pattern_contexts'))
+            self.searched_for_modifiers = True
 
     def register(self, func: Callable, template: str = None, order: int = 0) -> None:
         """
@@ -50,6 +56,7 @@ def register_decorator(self, func: Callable = None, **kwargs):
         return self.register(func, **kwargs)
 
     def get_for_template(self, template: str):
+        self.search_for_modifiers()
         modifiers = self[GENERIC_CM_KEY] + self[template]
         return sorted(modifiers, key=attrgetter(ORDER_ATTR_NAME))