Duplicated warnings in JetBrains editors

[rsalmei]

Problem

Hi, I think I've found one case where warnings are still duplicated, or perhaps is a regression.
I'm using 1.62.1, and I see them doubled on Pycharm (up to date, with Rust plugin up to date).
To simulate, just create a new binary project, and insert any use:

use std::sync::Arc;

fn main() {
    println!("Hello, world!");
}

Then, create a quick Run Configuration with cargo check --all-targets:

Note the "1 warning" on the left, but doubled on the complete output.
Also note that Pycharm uses JSON: cargo check --color=always --message-format=json-diagnostic-rendered-ansi --all-targets
On the terminal, I can reproduce with the exact same command, but not with either cargo check --color=always --message-format=json-diagnostic-rendered-ansi or cargo check --color=always --all-targets, hence I think the problem is on the interaction between these two options.

Thanks!

Steps

1. create a new bin project
2. insert any use
3. in Run -> Edit Configurations, add a cargo one with command: check --all-targets and your current workdir
4. run it (^R on macOS)

Possible Solution(s)

No response

Notes

No response

Version

No response

[weihanglo]

Thanks for your step-by-step report!

There are two rustc invocations in your reproducible example (a test target and a bin target. check them with --verbose flag on). Both of them emit the same "unused import" diagnostics.

The deduplication behaviour was introduced since 1.55 by #9675. Cargo deduplicates rustc diagnostics message with a rudimental hash-them-all approach. For formats not primary for human to consume, such as json and json-diagnostic-rendered-ansi, Cargo would leave them as-is in order to open a door for downstream tools to program. We might consider introducing a new flag --dedup-message or so to explicitly deduplicate all kinds of messages, though I tend to avoid adding a bunch of flags onto Cargo's already complex surface. IMHO the current status is a good balance between human-readability and extensibility.

I am going to close this. If anyone gets a different thought, please leave comment below and we can revisit it. Thank you!