Vscode-rust: Auto formatting dropping use statements

[Mossop]

I'm going to apologize in advance because this issue is probably not terribly helpful. All I can say is what I'm seeing, not what the specific circumstances are, but if there are ways I can help track that down I am super-willing to do legwork. If you just want to close this as providing not enough info then that's fine too.

I've been using this extension for a couple of weeks and have things set to format the code on save. Initially this seemed fine, but recently "use" statements have been getting removed from the source without me doing it. I don't know for sure that it is the rls extension but that is the only thing I can think of that is modifying the source frequently.

Worth noting that I am running with VSCode insider builds (currently 1.35.0-insider (1.35.0-insider)), RLS is at 0.6.1.

[Mossop]

I've also noted (just now in fact) that despite the file being saved before, making some changes to a comment and saving again changed the use statements, in this case it didn't remove any but it did add an extra newline between some.

[Mossop]

I managed to reproduce this. I've confirmed that RLS is dropping use statements, in the case I am seeing here when trying to reorder them. rustfmt from the command line shows the correct changes to apply, RLS makes a different change. This happens whether I format on save or run Format Document from the command palette.

Here is the file and the diff applied by rustfmt and the diff that RLS applied: https://gist.github.com/Mossop/58b8bd28e0be52440124ac78f819e933

[Mossop]

Updated the gist with a comment, I set rls to use the rustfmt from my path and it didn't drop a use statement but it didn't quite apply the same diff.

[sfackler]

I've seen this as well since the 1.35 release.

[nikonthethird]

I have a pretty minimal example:

use B::BA;
use self::A::AA;
use B::{BB, BC};

mod A {
    pub struct AA;
}

mod B {
    pub struct BA;
    pub struct BB;
    pub struct BC;
}

If you try to format these use statements using the latest stable RLS (with Format Document or Ctrl+Shift+i in Vs Code), this happens:

// Empty line remains here.
use self::A::AA;
use B::BA;

[nikonthethird]

I now found a case where the closing }; of a use block has been overwritten.

[hsfzxjy]

Same issue here. Is there any approach to temporarily avoid this?

[dpetrick]

I'm also experiencing destructive changes on uses and can provide more info if required. Downgrading the toolchain to 1.34.2 "fixes" the issue for me for now.

[crsmithdev]

I am also experiencing this issue.

[Celeo]

Same issue here. Is there any approach to temporarily avoid this?

You can create a rustfmt.toml file with reorder_imports = false in your project root.

[mike-engel]

I've noticed that if you reorder the imports by hand, it won't drop use statements unexpectedly. Takes a little time, but you can avoid adding a rustfmt.toml file until this issue is resolved

[viktorku]

Duplicate of #576

[Xanewok]

This is confirmed and fixed in Rust 1.36 (now in beta, will be released in a week), please try using 1.36 and reopen if that still occurs using that channel. Thanks for reporting this and sorry for the hassle!