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Moved LSP main loop to use tokio.#11036

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anlumo merged 27 commits intomasterfrom
anlumo/lsp-tokio
Apr 2, 2026
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Moved LSP main loop to use tokio.#11036
anlumo merged 27 commits intomasterfrom
anlumo/lsp-tokio

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@anlumo anlumo commented Mar 18, 2026 •
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@anlumo anlumo requested review from LeonMatthes and ogoffart March 18, 2026 15:03
@anlumo anlumo self-assigned this Mar 18, 2026
ogoffart
ogoffart reviewed Mar 19, 2026
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LeonMatthes
LeonMatthes reviewed Mar 19, 2026
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IMO, I think this is going in a good direction, it's a much less invasive change, but allows us to use normal async, which was the goal. 👍

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@anlumo anlumo force-pushed the anlumo/lsp-tokio branch 3 times, most recently from f4a09ae to 965802b Compare March 20, 2026 09:46
@anlumo anlumo marked this pull request as ready for review March 23, 2026 17:57
@anlumo anlumo requested review from LeonMatthes and ogoffart March 23, 2026 17:58
@anlumo anlumo force-pushed the anlumo/lsp-tokio branch from 1827475 to 8a8f9f6 Compare March 23, 2026 18:29
ogoffart
ogoffart reviewed Mar 24, 2026
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LeonMatthes
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This is going in a good direction. Some nitpicks left.

What I am concerned about most is our continued use of RefCell.
That seems incorrect in an async world (even before this change tbh).
Any ideas how we want to deal with this?

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anlumo commented Mar 24, 2026 •
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@LeonMatthes I agree that RefCell/Mutex/RwLock is bad code style and can cause a lot of troubles. However, the proper fix to this is to use channels, which means a major refactoring. This is exactly what I tried to do with the rewrite to async_lsp and a major reason for the large number of added lines in that PR. Maybe we can find a way to get smaller PRs that change to a new async architecture step by step?

@anlumo anlumo force-pushed the anlumo/lsp-tokio branch 2 times, most recently from 31df97b to 34f4f41 Compare March 25, 2026 15:25
@anlumo anlumo linked an issue Mar 25, 2026 that may be closed by this pull request
Move LSP to use async #11131
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@anlumo anlumo force-pushed the anlumo/lsp-tokio branch 2 times, most recently from f78b2a7 to f053d13 Compare March 26, 2026 09:52
LeonMatthes
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What I'm most curious about is why not continue using the fine-grained locking on the Context and use a large-scale lock. What is the advantage of that?

Apart from that it's mostly nitpicks left. 👍

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Comment thread tools/lsp/preview/connector/native.rs
ogoffart
ogoffart reviewed Mar 26, 2026
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@anlumo anlumo force-pushed the anlumo/lsp-tokio branch 5 times, most recently from a7a03af to dfaf3e5 Compare March 27, 2026 12:46
@anlumo anlumo requested review from LeonMatthes and ogoffart March 27, 2026 15:22
@anlumo anlumo force-pushed the anlumo/lsp-tokio branch from dfaf3e5 to 0fdd100 Compare March 30, 2026 17:22
anlumo and others added 25 commits April 1, 2026 19:14
@anlumo @LeonMatthes
Simplify crossbeam channel receiver.
2c41d76 
Co-authored-by: Leon Matthes <leon.matthes@slint.dev>
@anlumo
Replaced threads for the native preview with tokio tasks.
e309090
@autofix-ci @anlumo
[autofix.ci] apply automated fixes
15382df
@anlumo
Join lsp message receiver thread before terminating.
e94af18
@anlumo
Move LSP to have a idle timeout for recompiles instead of a debounce …
e3487b3 
…timer.
@anlumo
Fixed LSP startup, it has to run concurrently to the main task.
9642e52
@anlumo
Reverted process_input to use a thread again, because the native prev…
0495460 
…iew doesn't use tokio.
@anlumo
Fixed sending messages from the LSP to the native preview.
08f6965
@anlumo
Fixed a clippy warning.
0f5257b
@anlumo
Minor code cleanup.
1aa576f
@anlumo
Extraced the crossbeam-to-tokio-channel thread to its own function in…
0d9a3ed 
… the native LSP.
@anlumo
Moved LSP's Context to be mutexed as a whole rather than containing a…
0c4932c 
… bunch of RefCells.
@anlumo
Fixed clippy warnings.
f672ae6
@anlumo
Fixed slintpad compile errors.
8c6e60b
@anlumo
Minor code improvements in the LSP's main file.
5312954
@anlumo
FileWriter can't be used on wasm32, so just don't compile it.
e0f2224
@anlumo
Removed ContextOrDocumentCache, since it's not absolutely necessary.
064d250
@anlumo
Fixed test accurate_diagnostics_in_dependencies.
95cdd01
@anlumo
LSP's Context is no longer in an Arc or Rc, which simplifies the code…
f4e4394 
… by a lot.

Since we're single-threaded anyways, this shouldn't have any negative performance impact.
@anlumo
Fixed a warning when building for wasm32-unknown-unknown.
3844681
@anlumo
Moved handling LSP responses to the LSP message receiving thread, whi…
dd261a8 
…ch should fix some deadlocks.
@anlumo
Simplified startup, since we no longer need to handle requests and no…
68d6123 
…tifications at that point.
@anlumo
Adapted LSP's wasm main to handle the new lockfree Context.
18965d1
@anlumo
Fixed a warning with certain feature configurations.
58e6a74
@anlumo
Join the crossbeam adapter thread on LSP shutdown.
b6c042a
@anlumo anlumo force-pushed the anlumo/lsp-tokio branch from e6f399a to b6c042a Compare April 1, 2026 17:15
LeonMatthes
LeonMatthes approved these changes Apr 2, 2026
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Super cool that you managed to get rid of the Rc/RefCell situation all together 👍

As discussed this linearizes all requests at the moment, but as we discussed, that's not necessarily a bad thing, as this was all single-threaded anyhow.

@anlumo anlumo merged commit d451604 into master Apr 2, 2026
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@anlumo anlumo deleted the anlumo/lsp-tokio branch April 2, 2026 12:25
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Move LSP to use async

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