Autocomplete seems broken by a LazyLock + conditional crate paths

[alice-i-cecile]

rust-analyzer version: rust-analyzer 1.83.0 (90b35a6 2024-11-26)

rustc version: 1.83

editor or extension: VsCode

relevant settings: (eg. client settings, or environment variables like CARGO, RUSTC, RUSTUP_HOME or CARGO_HOME)

repository link (if public, optional): bevyengine/bevy@760d0a3, which is the commit that broke this.

code snippet to reproduce:

use bevy::prelude::*;

fn my_system(query: Query<&Transform>){
    for transform in query.iter(){
      // Autocomplete should show up here, showing the various fields etc.
       transform
   } 
}

First detected in bevyengine/bevy#17004. We can probably work around this, but this seems to be an RA bug.

[ChayimFriedman2]

I'm trying to understand what's the role of the LazyLock here. Is it created in a bad state in which proc macros expand to something not completeable, then after edits becomes good?

[alice-i-cecile]

@mockersf @raldone01 may have better hypotheses than I do here about what's going on: bevyengine/bevy#16766 was the offending PR.

[ChayimFriedman2]

I tried and I'm getting completions normally (Windows), both in 0.15.0 and in this commit.

[raldone01]

I can look into it in the new year.

I will try to reproduce it on my machines.

Seems very weird.
I just read: bevyengine/bevy#17004

Seems like RA keeps the proc macros instantiated across crates which rustc does not.

[ChayimFriedman2]

Indeed it does, because r-a analyzes all crates at once while rustc compiles one crate at a time. In general proc macros should not rely on external state, and their behavior if they do is non-guaranteed, even in rustc. So if this is the problem I believe it's working as intended.

[Veykril]

rust-analyzer caches proc-macro expansions unlike rustc, it also doesn't unload the library unlike rustc. You generally cannot assume when and how often a proc-macro gets re-executed. The only thing you may assume is the environment (env vars, working directory) which is also not ideal but cargo is not going to change the working directory anymore now (the breakage would be too severe if they tried).

[alice-i-cecile]

Awesome, thanks for the help and feedback :) I'm happy to call this an "us problem"; I hope this thread helps some poor soul years down the line.