formatting is blocked behind build?

[MahdiBM]

Describe the bug
I'm not sure if this sourcekit-lsp's doing or this extension's.
When I trigger a build, then immediately trigger a format, it appears that the document-format action always waits for the build to complete.

To Reproduce
Steps to reproduce the behavior:
Trigger a build.
Trigger "Format Document".

Expected behavior
Formatting should not be stuck behind a build.

Environment
Sourcekit-lsp settings:

{
  "backgroundIndexing": true,
  "backgroundPreparationMode": "build",
  "maxCoresPercentageToUseForBackgroundIndexing": 0.7,
  "experimentalFeatures": ["on-type-formatting"]
}

"backgroundPreparationMode": "build", might have a role in this beahvior?

Additional context
Add any other context about the problem here.

[plemarquand]

I think this is a sourcekit-lsp behaviour, transferring issue to that repo.

[ahoppen]

Synced to Apple’s issue tracker as rdar://141559494

[MahdiBM]

@ahoppen how should I go around debugging this? Any tips?

[ahoppen]

What I would do is

• Run log stream --predicate 'subsystem CONTAINS "sourcekit-lsp"' --level debug --signpost
• Reproduce the issue
• Safe the output from log stream to a file, eg. /tmp/log.txt
• Convert the signposts into a trace using sourcekit-lsp debug trace-from-signposts
• Open the trace in https://ui.perfetto.dev

There you should see a timeline of the requests and you can see which request might be blocking other requests. MessageHandlingDependencyTracker.swift is the relevant file that defines request/notification dependencies.

I think the trace-from-signposts is only available in Swift 6.1-aligned SourceKit-LSP releases but the signposts might be logged on older SourceKit-LSP versions as well, I’m not entirely sure. Also, this debugging utility currently only works on macOS.

[MahdiBM]

I seem to be unable to reproduce this on swift-6.1-DEVELOPMENT-SNAPSHOT-2024-12-21-a.

[MahdiBM]

@ahoppen perhaps we should have a label like "awaiting-release"?
Because there is also the other formatting issue which you reopened since the changes were not released yet.