In which cases can a Dictionary go into read-only mode?

renevanderark · June 14, 2026, 3:17pm

Godot Version

4

Question

I run into this every now and then. I have a suspicion that in my case the Dictionary value which I typed as a Node class (that automatically seems to get assigned NodePath) is freed, which may trigger read-only mode.. but then again, it may have a different reason.

Can someone point me to source code that turns on read-only mode for Dictionaries?

Or is it only while iterating over keys for instance?

Frozen_Fried · June 14, 2026, 3:35pm

Are you looking for this?

github.com/godotengine/godot

core/variant/dictionary.cpp

master


      
          }
          
          Dictionary Dictionary::duplicate(bool p_deep) const {
          	return recursive_duplicate(p_deep, RESOURCE_DEEP_DUPLICATE_NONE, 0);
          }
          
          Dictionary Dictionary::duplicate_deep(ResourceDeepDuplicateMode p_deep_subresources_mode) const {
          	return recursive_duplicate(true, p_deep_subresources_mode, 0);
          }
          
          void Dictionary::make_read_only() {
          	if (_p->read_only == nullptr) {
          		_p->read_only = memnew(Variant);
          	}
          }
          bool Dictionary::is_read_only() const {
          	return _p->read_only != nullptr;
          }
          
          Dictionary Dictionary::recursive_duplicate(bool p_deep, ResourceDeepDuplicateMode p_deep_subresources_mode, int recursion_count) const {
          	Dictionary n;

renevanderark · June 14, 2026, 3:50pm

More specifically in which cases the core engine calls this, because it seems to be triggered by edge cases.

I can assume while it is being accessed to be iterated so it cannot be mutated from another thread…

Yet sometimes a dict seems to get stuck in this state.

normalized · June 14, 2026, 9:15pm

Afaik the only case aside from declaring it const may be when the dictionary is in a resource loaded at runtime.

renevanderark · June 14, 2026, 10:57pm

Thanks.. I will keep observing the pattern. It is of course caused by plugin development choices during edit time.

normalized · June 14, 2026, 10:59pm

Do you (de)serialize the dictionary in question?

renevanderark · June 15, 2026, 4:33am

Not proactively no.

I suspect another culprit then. Maybe an npe somewhere.

I get no stacktrace… Can I get that in console mode?

renevanderark · June 15, 2026, 10:27am

Culprit found:

setting a default value will cause
the reference to be lost when the revert button is clicked (i.e. there is a dangling reference to the old Dictionary in the plugin code → and this dangled about Dict is read-only don’t touch now)
until the scene is closed and reopened again