[3.x] Implement textual ext/subresource IDs.

[akien-mga]

• Friendlier with version control.
• Generates pseudo unique IDs, to minimize conflicts when merging, but still user readable (so, not UUID).
• Eventually will also allow to have more precisely named sub-resources in imported files.
• This will allow better reloading on changes (including resources already loaded) as well as better keeping track of changes on the DCC.
• Keeps compatibility with the old formats.

Backport of #50676.

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IMPORTANT: Needs extensive testing on safe project backups. If there's a bug in this PR, it can break scene files and lead to data loss. So make copies of your projects (or better, use VCS) when testing this PR. But please do test it on your projects to make sure that it works as expected :)

How to test: See Testing pull requests for instructions on how to download CI builds to test locally.

[steffendietz]

Just wanted to provide feedback regarding this PR:

• I built the PR branch from source
• before every test I git reset --hard my test project to observe changes

Test1

• Opened the test project -> git status showed no changes
• Played the project (F5) -> assets/theme.tres, default_env.tres and scenes/PlayingField.tscn (main scene) were updated to the new format

Test2

• Opened the test project -> git status showed no changes
• Closed the initially opened main scene (scenes/PlayingField.tscn)
• Played the project (F5) -> only default_env.tres was updated to the new format

Test3

• Opened the test project -> git status showed no changes
• Closed the initially opened main scene (scenes/PlayingField.tscn) and opened another scene (scenes/Pedestal.tscn)
• Played the project (F5) -> default_env.tres and scenes/Pedestal.tscn were updated to the new format

Observations

The project ran without problems.
The updates to the new format only took place when running the project, not when merely opening the scenes in the editor.

[akien-mga]

Updated to match the latest state from #50676.

The updates to the new format only took place when running the project, not when merely opening the scenes in the editor.

That's expected indeed, changes only happen when the scenes or resources are saved. Some are saved automatically when you run the project, which is why you saw them changing.

[Calinou]

Here are Windows x86_64 builds of this pull request for testing:

• Editor: https://0x0.st/-yty.zip ^{(link expires in October 2021)}
  • The binary is larger than usual (218 MB). It contains full debugging symbols, which is required to get accurate backtraces if Godot crashes. It's also less optimized than official binaries.

I would recommend testing this PR with an exported project as well. (The project must be exported with an editor build that includes this pull request.)

• Debug export template: godot.windows.opt.debug.64.exe.zip
• Release export template: godot.windows.opt.64.exe.zip

[akien-mga]

Closed by mistake.

[Calinou]

If this is to be merged for 3.5, beware of #54774.

[theludovyc]

Hello 😊 ! How can I help to close this one ? :)

[Calinou]

Hello blush ! How can I help to close this one ? :)

3.5 is too close to release for this pull request to be merged by now.

This PR could still be considered for 3.6, but this is a fairly risky change to undertake. We also can't revert this change once it is made in a released beta/RC build, as the new UID-based format is incompatible with non-UID-aware versions of Godot.

For this PR to be merged in a 3.6 beta, there needs to be strong community demand and people available to test this change on their real world projects (after making backups, of course 🙂).

Also, this PR will need be rebased and have UID fixes that were applied in master cherry-picked before this can be merged. (I can't find the PRs for those fixes right now, but I remember seeing a few.)

[theludovyc]

This PR could still be considered for 3.6, but this is a fairly risky change to undertake.

Why ?

For this PR to be merged in a 3.6 beta, there needs to be strong community demand and people available to test this change on their real world projects (after making backups, of course 🙂).

Got it ;) !

[Calinou]

Why ?

This PR changes how scene files are saved, which has a risk of data loss if there are bugs in the implementation. Some people still aren't using version control in their projects, and while Godot's license doesn't provide any warranty, we should still avoid playing with fire when possible.

[akien-mga]

After thinking about this some more, I think it's not worth backporting to 3.x anymore.

We're about to release 3.5 and this is of course too late to merge such a change. It could be merged for 3.6, but there are various issues that this would raise:

• It creates forward compatibility issues for earlier Godot releases, as scenes opened in a hypothetical 3.6 release with this change would no longer be compatible with 3.5 and earlier. It's fairly common (for me at least) to open projects in older releases when checking if a new bug is an engine regression or not (i.e. did it work fine in 3.4? In 3.5 beta1? In 3.5 RC2? etc.).
• There are still unresolved bugs with this implementation in master (e.g. Duplicated files or resources retains the same UID #54774), so it's not ready for the 3.x branch unless we can really commit to fixing those bugs in a timely manner. Some bugs might not have been well described yet because master is still in alpha so bugs with the UID system can be hidden by other bugs that are on top of it.
• It's a nice-to-have, but not critical for making games with 3.x and changing the workflow in what would likely be the last minor release in 3.x doesn't seem really useful.