Don't pass --all-targets when a target is specified

[mo8it]

We apply a target in this line:

rust-analyzer/crates/rust-analyzer/src/flycheck.rs

Line 411 in 4221354

match tgt {

But then, apply_on_command is called in this line:

rust-analyzer/crates/rust-analyzer/src/flycheck.rs

Line 435 in 4221354

options.apply_on_command(&mut cmd);

apply_on_command adds --all-targets if the config value all_targets is true (which is the default).

Sadly, Cargo currently ignores any target specification like --bin BIN_NAME if --all-targets is specified. Which means that PR #17912 is ineffective right now.

So what is the solution? Don't pass --all-targets when a specific target is passed? This currently can't be the solution.

The first problem is that when not using --all-targets and without --profile test, Cargo doesn't check tests with #[cfg(test)]. So we should (always?) add --profile test to cargo check?

The second problem is that Rust-Analyzer seems to forget all errors and warnings after an invocation of cargo check. See the video from VS-Code in a Windows VM with the pre-release Rust-Analyzer extension:

Screencast.from.2024-09-13.15-47-18.webm

In this video, I disabled all_targets in the extension settings. When Rust-Analyzer starts, it runs cargo check and collects 113 errors and 8 warnings. Then, while still starting up, it forgets all these errors and warnings and runs cargo check again until it reaches the same 113 errors and 8 warnings that it already had!?

But this isn't the main issue here. The issue is that, after saving one file associated with a binary, Rust-Analyzer runs cargo check --bin if1 quickly as expected from #17912 but it forgets all diagnostics it had before about the other targets!

TL;DR

• We need to omit --all-targets when specifying a specific target like --bin.
• We need to pass --target test to the check command.
• Rust-Analyzer shouldn't forget all diagnostics from other targets.
• (Why does Rust-Analyzer run cargo check twice on startup?)

CC @alibektas @Veykril from the other PR.