Annoying error message in workspaces containing non-rust folders

[Timmmm]

If you have a workspace containing some rust and some non-rust folders (for example a Rust backend and non-Rust frontend of some sort), then you get this error every time you open the workspace:

rust-analyzer failed to load workspace: can't find Cargo.toml at /path/to/nonrust/folder

Gets pretty annoying!

[ruabmbua]

I think you also get this error, if you open an arbitrary folder with VScode, which contains at least some rust code, but no top level Cargo.toml

[matklad]

Yeah... It's unclear what's the best fix here, as it's pretty important to issue this warning if we legitimately fail to find Cargo.toml...

Perhaps we should allow to suppress this notification on a per-project basis?

[p-avital]

I agree that per-project suppression is the way to go.
Maybe using a setting can help, and having a button in the notification to add the suppression setting in workspace preferences? That way people who want to disable it globally can just enable said setting in their global preferences?

[Timmmm]

Could you delay starting rust-analyzer until a .rs file is opened within each project?

[TheZoq2]

Could you delay starting rust-analyzer until a .rs file is opened within each project?

This seems reasonable to me. Currently, my vim asks if I want to start cargo watch when I open any file in a rust folder, even things like commit message edits

[luser]

Ideally rust-analyzer wouldn't try to operate at all on a workspace that doesn't contain Rust code. rls-vscode handles this by using workspace.onDidOpenTextDocument to watch for Rust source files, finding the matching workspace, and starting a process to handle that workspace if it's not already open.

As a minor band-aid, perhaps the errors could be stored instead of displayed immediately, and then only display an error if no workspaces were loaded?
https://github.com/rust-analyzer/rust-analyzer/blob/cecf25b72f2af84fc1535cf52d6f3c1b52802565/crates/rust-analyzer/src/main_loop.rs#L106

[kynrai]

Just came across this too. as @luser said, a similar approach rls-vscode takes might be the better option here. some workspaces can get very large so so scanning each project seems unnecessary

[davidolrik]

I get this error when opening workspaces with no rust code at all.

[jondo2010]

Just chiming in here, this is a fairly common use-case. Imagine doing some work that entails porting an existing c library to Rust -- I'll have two folders open in the workspace, only one of which is my Rust project.

[lnicola]

@Timmmm, @jondo2010 this somehow seems to work now, can you please test again?

(Marking S-actionable, if you look at this in the future and the OP hasn't answered, ping me so we can close it.)

[Timmmm]

Yeah I don't seem to get that error anymore either. Guess we can close this.