If a resource is used as a key in a dictionary, it will be replaced by null when saving with ResourceSaver to a .tres file

[iamtoaster]

Godot version

4.0.alpha1

System information

Windows 10

Issue description

If you have a custom resource with exported dictionary in it (let's call it ResB), and you use another custom resource as a key on that dictionary (ResA), then try to save it in .tres format, the resource that was used as a dictionary key will not be saved (replaced by a null) and following message will be printed to console:

  <Ошибка C++>   Method/function failed. Returning: "null"
  <Исходный код C++>scene/resources/resource_format_text.cpp:1509 @ _write_resource()
  <Трассировка стека>Main.gd:19 @ _ready()

I also found that this error only happens when you try to save to a .tres file. When I tried to save same resource to a binary .res everything worked as expected with resource being saved.

Also found that if you use that same resource (ResA) for more than as a dictionary key (say, in an exported variable) in the resource being saved (ResB) then the bug does not happen either.

Steps to reproduce

1. Create two custom resources (ResA and ResB)
2. Make sure ResB has an exported dictionary which uses instances of ResA as keys.
3. Add at least 1 entry to the dictionary in ResB that uses an instance of ResA as a key.
4. Try to save ResB to a .tres file using ResourceSaver.save("res://data.tres", ResBInstance)

Minimal reproduction project

ResourcesTest.zip
Simply run it. res://data.tres is the buggy output file, res://data.res is the same resource but in binary format (and also no bug)

[Bashar-Ahmed]

If this issue is available, then I would like to attempt this as a first contribution.

[Calinou]

If this issue is available, then I would like to attempt this as a first contribution.

Feel free to look into fixing this 🙂

[Calinou]

@Anaxan Please don't derail other issues that are unrelated to this particular bug.

[Anaxan]

I apoligize for any offense I've caused. That wasn't my intention.

[iamtoaster]

I just found out this bug is also present on Godot 3.4.2 stable, can be reproduced with the same project (just remove the @ part of @exports and it will work)

[Bashar-Ahmed]

As far as I was able to gather the issue, the path_cache is NULL when the ResourceFormatSaverTextInstance::_write_resource is being called. Is this how it was meant to be?, because the path_cache is the path from which the resource is to be loaded. So what does it signify during saving a Resource. To correct this, we can set path_cache within the ResourceFormatSaverTextInstance::save function, but since the resource passed in the argument is const I was unable to figure out a way of doing it. Any potential solutions?

[Life4gal]

Hi everyone, I have a PR that solved this problem.

see #64812 :)

[Life4gal]

By the way, I came across this issue because of a bug of RSCC :)

[Prakkkmak]

I get the same issue on 4.2.2.stable, i used the my_data.tres as key of my dictionary and the references where null. I have changed keys to my_data.id and now it's working.

Another ismular issue : https://forum.godotengine.org/t/resources-being-set-to-null-in-game/45678