Unresolved module rust-analyzer error.

[RamiHg]

Hello,

Ever since the latest update, I've been getting strange "unresolved module rust-analyzer" errors on lines that define modules. E.g.:

pub mod foo;  // unresolved module rust-analyzer
mod bar;
mod foobar; // unresolved module rust-analyzer

The problem occurs in only one library in my workspace. A seemingly random subset of 1-9 module defines have that error. Every time I restart VSCode, a slightly different subset of those 1-9 have that error. If a module has that error, rust-analyzer does not work for that module (no autocomplete, hints, etc).

There are no errors in the Rust Analyzer Language Trace, except for [ERROR ra_project_model] cyclic dependency <unrelated module> -> <unrelated module>. But that error has been there for months, and I suspect it's a separate issue (they are both dev-dependencies of one another).

I am however seeing errors in the "Extension Host" log. I've attached the full log (ra_errors.txt) with the callstack, but here are some of the error messages:

[2020-07-21 21:37:18.304] [exthost] [error] [matklad.rust-analyzer] provider FAILED
[2020-07-21 21:37:18.305] [exthost] [error] Error: Illegal value for `line`
...

[2020-07-21 21:35:45.772] [exthost] [error] [matklad.rust-analyzer] provider FAILED
[2020-07-21 21:35:45.773] [exthost] [error] Error: canceled by client
...

[2020-07-21 21:38:35.832] [exthost] [error] [matklad.rust-analyzer] provider FAILED
[2020-07-21 21:38:35.832] [exthost] [error] Error: content modified

Windows 10, rustc 1.45, rust-analyzer v0.2.248.

[bjorn3]

Which VSCode version are you using?

[RamiHg]

The latest version at the time of this post. 1.47.2.

[DouglasLivingstone]

I'm seeing this too, closing and re-opening the lib.rs file hides the error until lib.rs is edited. I'm also using VS Code 1.47.2 and rust-analyser 0.2.248.

[RamiHg]

I've been trying to figure out what's going on for the last couple of days to no avail. I've removed projects one-by-one from my workspace, removed the circular dev-dependencies, turned off all features, turned on all features, turned off proc-macro expansion, etc. I also enabled trace server logging, but nothing stood out to me. No error messages coming from the server at all.

When I tried building from source (to see if maybe the bug had been fixed), I ran into #5556. Could the two issues be related? The weird syntax errors happen to correlate with the modules I've been having problems with:

I'm happy to help give more information in any way I can. This bug is making RA unusable ATM :(. I'm having to gasp use RLS just to get some code-completion.

[wansa9]

I'm seeing the same issue, VS Code 1.47.3, rust-analyzer 0.2.256.

[lnicola]

@RamiHg is your project public so we could try to reproduce this? If not, could you try to minimize it (e.g. by removing modules, types, replacing function bodies with loop {}) until it no longer happens, or you're able to share the code?

[DouglasLivingstone]

The smallest reproducible example I have is attached. To reproduce:

1. Extract the zip file to repo
2. Open VS Code, eg code repo
3. Open b/src/lib.rs
4. Close VS Code
5. Reopen VS Code

Should see:

It seems to be fine if lib.rs is not open when VS Code opens, so could this be a race condition somewhere?

repo.zip

[lnicola]

It might be a race, as I couldn't reproduce it:

Does it get fixed if you reopen or edit the file? Does it ever happen again after startup?

[DouglasLivingstone]

If I close and reopen the file, the error is not shown until I edit it. The error is shown before save.

If I close all files, close VS Code, reopen VS Code, reopen lib.rs, add a new file y.rs, then add mod y; to lib.rs, then I get this state:

Closing lib.rs hides the error (so the file name on the left goes white). If I reopen the file, initially there is no error shown:

but if I edit the file, then it goes back to the first screenshot, with an error for y. If I open lib.rs then restart VS Code, both modules are highlighted:

[DouglasLivingstone]

Also, if I delete the a package and remove it from the top-level Cargo.toml workspace section, then the lib.rs file works totally fine after restarting VS Code.

[RamiHg]

It might be a race, as I couldn't reproduce it:

Does it get fixed if you reopen or edit the file? Does it ever happen again after startup?

@DouglasLivingstone that looks like exactly the same steps + weird behavior that I encountered! @lnicola: I should mention that this was only happening on Windows. I could not reproduce the bug on either Mac OS or Linux. If you can't reproduce the bug with @DouglasLivingstone's use-case, I'll just make my repo public.

[Kimundi]

I can also confirm this behavior.

[pragmatrix]

I had the same problem with a nested library package. After starting up VSCode and editing the lib.rs file, it showed a number unresolved module errors and the problem always appeared when I opened VSCode without the lib.rs opened in the editor. When lib.rs was opened and the frontmost file in the VSCode, everything worked as expected.

I tracked the problem down to a path normalization problem related to Vfs / FileSets. In my system, some paths enter the rust-analyzer with lowercase drive letters (in this case c:). After converting them to uppercase at two points in the code, the problem disappeared entirely. May be this helps tracking down the root cause from there.

Edit: I've isolated the problem to the VfsPath::encode function: f0d511e

[Johnrobmiller]

This bug replicated for me as of 1/3/2024. I fixed it simply by closing and reopening VSC.