Add a warning when registering proxy plugins for fetching

Author: matthiask

CHANGELOG.rst

@@ -6,6 +6,10 @@ Change log
 Next version
 ~~~~~~~~~~~~
 
+- Added a warning when registering a proxy plugin with the ``RegionRenderer``
+  with ``fetch=True``. Users should only register the concrete plugin directly
+  for fetching, otherwise duplicated plugins are very likely while rendering.
+
 
 5.4 (2025-06-19)
 ~~~~~~~~~~~~~~~~

feincms3/renderer.py

@@ -194,6 +194,12 @@ def register(
                     stacklevel=2,
                 )
 
+            if p._meta.proxy and fetch:
+                warnings.warn(
+                    f'The plugin {p} is a proxy but is also registered with the default "fetch=True". This can cause plugins to be fetched (and rendered) twice.',
+                    stacklevel=2,
+                )
+
             self._plugins[p] = (p, renderer, subregion, marks, fetch)
 
     def plugins(self, *, fetch=True):

tests/testapp/test_oldregions.py

@@ -8,23 +8,31 @@
 from testapp.models import HTML, Page
 
 
-class Text(SimpleNamespace):
+class Meta:
+    proxy = False
+
+
+class Plugin(SimpleNamespace):
+    _meta = Meta
+
+
+class Text(Plugin):
     pass
 
 
-class Teaser(SimpleNamespace):
+class Teaser(Plugin):
     subregion = "teasers"
 
 
-class FAQ(SimpleNamespace):
+class FAQ(Plugin):
     subregion = "faq"
 
 
-class Command(SimpleNamespace):
+class Command(Plugin):
     subregion = ""
 
 
-class File(SimpleNamespace):
+class File(Plugin):
     pass
 
 

tests/testapp/test_region_renderer.py

@@ -211,17 +211,20 @@ def handle_section(self, plugins, context):
             content = self.render_section_plugins(section, plugins, context)
             return f"<section>{''.join(content)}</section>"
 
+    class Meta:
+        proxy = False
+
     class Text:
-        pass
+        _meta = Meta
 
     class Image:
-        pass
+        _meta = Meta
 
     class Section:
-        pass
+        _meta = Meta
 
     class CloseSection:
-        pass
+        _meta = Meta
 
     renderer = SectionRenderer()
     renderer.register([Text], "Text")  # Register as list