Fix Script Editor saves C# files as embedded scripts.

[nongvantinh]

fixes: #88543
fixes: #88160

Because of the limitations of compiled programming languages like C#, when a newly created *.cs file hasn't been compiled, we don't have any information about its Path or Type in the assembly. This means we end up creating an invalid instance of this file whenever there's a request. Consequently, multiple instances of the script can exist. When a new instance takes over the path, it clears the path_cache of the previous instance, leading to undefined behavior.

[KoBeWi]

If other instances of the script exist, taking over path will make them unlinked from the original resource. It might cause attached scripts to stop updating (relevant for tool scripts).

[nongvantinh]

If other instances of the script exist, taking over path will make them unlinked from the original resource.

Just to clarify, the only scenario in which C# creates a different instance rather than using the previous one is when the C# script has not yet been compiled. Once it is compiled, there will be only one instance. I'm not sure about other scripting languages, though.

[KoBeWi]

So I just realized

During the ResourceLoader::load process, the C# side creates a different instance and clears the path_cache of the old one, causing it to lose its path.

This points to a bug in C# loader, because CACHE_MODE_IGNORE is not supposed to do that.

[nongvantinh]

Thanks for pointing this out, the new PR should correctly and safely fix the bug and any future bugs related to multiple instances of C# script.

[KoBeWi]

While this works, it's not exactly how it should be implemented.
The code you added should take effect only when p_cache_mode is CACHE_MODE_IGNORE. Otherwise the new script should normally take over path.

[nongvantinh]

Thanks. I was completely ignored the p_cache_mode parameter since it wasn't being used before. Now, I have modified it according to the latest document specifications. Please help me test it thoroughly.

[akien-mga]

Thanks!