refactor: do not call URLResolver._populate() if not needed

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Release notes
 
+## v0.143.1
+
+#### Fix
+
+- Make django-component's position in Django's `INSTALLED_APPS` more lenient by not calling Django's `URLResolver._populate()` if `URLResolver` hasn't been resolved before ([See thread](https://discord.com/channels/1417824875023700000/1417825089675853906/1437034834118840411)).
+
 ## v0.143.0
 
 #### Feat

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "django_components"
-version = "0.143.0"
+version = "0.143.1"
 requires-python = ">=3.8, <4.0"
 description = "A way to create simple reusable template components in Django."
 keywords = ["django", "components", "css", "js", "html"]

requirements-dev.txt

@@ -12,8 +12,6 @@ asv==0.6.5
     # via -r requirements-dev.in
 asv-runner==0.2.1
     # via asv
-backports-asyncio-runner==1.2.0
-    # via pytest-asyncio
 build==1.3.0
     # via asv
 cachetools==6.2.0

src/django_components/extension.py

@@ -1163,9 +1163,7 @@ class ExtensionManager:
         extensions_url_resolver.url_patterns = urls
 
         # Rebuild URL resolver cache to be able to resolve the new routes by their names.
-        urlconf = get_urlconf()
-        resolver = get_resolver(urlconf)
-        resolver._populate()
+        self._lazy_populate_resolver()
 
         # Flush stored events
         #
@@ -1190,6 +1188,22 @@ class ExtensionManager:
             getattr(self, hook)(data)
         self._events = []
 
+    # Django processes the paths from `urlpatterns` only once.
+    # This is at conflict with how we handle URL paths introduced by extensions,
+    # which may happen AFTER Django processes `urlpatterns`.
+    # If that happens, we need to force Django to re-process `urlpatterns`.
+    # If we don't do it, then the new paths added by our extensions won't work
+    # with e.g. `django.url.reverse()`.
+    # See https://discord.com/channels/1417824875023700000/1417825089675853906/1437034834118840411
+    def _lazy_populate_resolver(self) -> None:
+        urlconf = get_urlconf()
+        root_resolver = get_resolver(urlconf)
+        # However, if Django has NOT yet processed the `urlpatterns`, then do nothing.
+        # If we called `_populate()` in such case, we may break people's projects
+        # as the values may be resolved prematurely, before all the needed code is loaded.
+        if root_resolver._populated:
+            root_resolver._populate()
+
     def get_extension(self, name: str) -> ComponentExtension:
         for extension in self.extensions:
             if extension.name == name:
@@ -1221,12 +1235,8 @@ class ExtensionManager:
             all_urls.append(urlpattern)
             did_add_urls = True
 
-        # Force Django's URLResolver to update its lookups, so things like `reverse()` work
         if did_add_urls:
-            # Django's root URLResolver
-            urlconf = get_urlconf()
-            root_resolver = get_resolver(urlconf)
-            root_resolver._populate()
+            self._lazy_populate_resolver()
 
     def remove_extension_urls(self, name: str, urls: List[URLRoute]) -> None:
         if not self._initialized:

src/django_components/util/testing.py

@@ -585,5 +585,11 @@ def _clear_djc_global_state(
     if gc_collect:
         gc.collect()
 
+    # Clear Django's URL resolver cache, so that any URLs that were added
+    # during tests are removed.
+    from django.urls.resolvers import _get_cached_resolver  # noqa: PLC0415
+
+    _get_cached_resolver.cache_clear()
+
     global IS_TESTING  # noqa: PLW0603
     IS_TESTING = False

tests/test_extension.py

@@ -5,6 +5,7 @@ import pytest
 from django.http import HttpRequest, HttpResponse
 from django.template import Context, Origin, Template
 from django.test import Client
+from django.urls import get_resolver, get_urlconf
 
 from django_components import Component, Slot, SlotNode, register, registry
 from django_components.app_settings import app_settings
@@ -649,6 +650,12 @@ class TestExtensionHooks:
 
 @djc_test
 class TestExtensionViews:
+    @djc_test(components_settings={"extensions": [DummyExtension]})
+    def test_resolver_not_populated_needlessly(self):
+        urlconf = get_urlconf()
+        resolver = get_resolver(urlconf)
+        assert not resolver._populated
+
     @djc_test(components_settings={"extensions": [DummyExtension]})
     def test_views(self):
         client = Client()