Warnings in the watch mode

[alex35mil]

I have N warnings in the app. I run rescript watch - it shows all of them and editor integration shows all of them as well. Then I save some file in the editor, and all of the warnings disappear from diagnostics.

This is what I see in the console:

After each consequent save, compiler stops outputting warnings - I guess it's related to the reason they disappear from editor diagnostics?

---

Also, two kinda unrelated remarks:

1. Feedback time - from save to update - noticeably increased compared to v11. Is this expected or is it something with my setup?
2. Seems like if I have 3 packages in a workspace, each package has own namespace in editor integration? With Rewatch, I hoped to get workspace wide diagnostics as it's done in rust-analyzer, but apparently it's not how it works in ReScript LSP?

[nojaf]

Could you share some more details, at first glance I don't have these problems.
N warnings stay visible on edits in watch mode and my editor keeps highlighting them.
I assume so, but do you have latest rescript npm package? Are you on prerelease editor tooling?
What is LSP client? Operating system?

---

1. I can't say much about that, never used v11.
2. ReScript LSP will only capture diagnostics for any open files. I suppose this is somewhat historically, unfortunately the LSP server does not have the same context as rescript watch has. Nor do they communicate.

[alex35mil]

Sure, I recorded video illustrating the issue - things are quite racy.

Context:

• a workspace with 3 packages (2 apps and 1 shared lib)
• editor: neovim
• rescript: v12.0.2 (from npm)
• rescript-language-server: v1.72.0 (installed via mason)
• os: macOS

Quick rundown:

1. I do rescript clean && rescript watch -> all warnings from 1 app appear: 1/9 (1 in the current file, 9 total in the current package)
2. I save the file -> only 1 warning from the current file remains
3. I save again -> console reprints only 1 warning from the current file
4. I open file with no warnings and hit save -> all warnings disappear from both - editor and console
5. I save again -> console reprints 4 warnings which appear in the editor
6. I save again -> all warnings are gone
7. I save again -> console reprints 4->7 warnings which appear in the editor
8. etc

FWIW there are around 90 warnings across the workspace - sometimes editor can show all of them, but it's rare.

CleanShot.2026-01-08.at.11.46.51.mp4

[nojaf]

Thanks, this is helpful! I can't explain all of it but you see the 9 error of the package after the initial build and I believe rewatch will only show you the warnings of the changed files in subsequent entries.

The same might be true for the editor warnings, initially these probably come from the .compiler.log file and we read all of them. Subsequently, we only take them from the open files into account and most likely clean up those of non-open files.

I haven't fact checked this yet, but that is my current train of thought.

[alex35mil]

ReScript LSP will only capture diagnostics for any open files

I guess it's partially explains what's happening. Yesterday, I didn't have any files with warnings opened in the editor, so 3 consecutive saves gave me zero warnings in the editor diagnostics. Today, I had some buffers with warnings opened, and it resulted in 4/7 reported warnings after double-save dance.

[dkirchhof]

Is it a monorepo?
I observed that editing files of a package generated only warnings of this one - not of all packages.

[cknitt]

Easy to reproduce even without monorepo:

Let's say I have A.res and A.resi with some unused variable warning in A.res.

When re-saving A.res, this unused variable warning still shows up.
When saving a different file B.res, the warning disappears.

[nojaf]

Is there a link between A and B in your example?

[cknitt]

Is there a link between A and B in your example?

No

[cristianoc]

do you need both .res and .resi to exist to repro?

[cknitt]

Actually no, I should have been clearer on that. Just had the .resi because I wanted something unused (unexported) at the top level of the module.

This works just as well to reproduce without .resi (unused x):

let f = () => {
  let x = 42
}