internal: Log flycheck errors

[ShoyuVanilla]

Resolves #16969

The non-cargo messages are appended to the error strings here;

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

Lines 460 to 482 in 7a8374c

	fn from_line(line: &str, error: &mut String) -> Option<Self> {
	let mut deserializer = serde_json::Deserializer::from_str(line);
	deserializer.disable_recursion_limit();
	if let Ok(message) = JsonMessage::deserialize(&mut deserializer) {
	return match message {
	// Skip certain kinds of messages to only spend time on what's useful
	JsonMessage::Cargo(message) => match message {
	cargo_metadata::Message::CompilerArtifact(artifact) if !artifact.fresh => {
	Some(CargoCheckMessage::CompilerArtifact(artifact))
	}
	cargo_metadata::Message::CompilerMessage(msg) => {
	Some(CargoCheckMessage::Diagnostic(msg.message))
	}
	_ => None,
	},
	JsonMessage::Rustc(message) => Some(CargoCheckMessage::Diagnostic(message)),
	};
	}
	error.push_str(line);
	error.push('\n');
	None
	}

that one is formatted into Err here;

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

Lines 144 to 155 in 7a8374c

	pub(crate) fn join(mut self) -> io::Result<()> {
	let _ = self.child.0.kill();
	let exit_status = self.child.0.wait()?;
	let (read_at_least_one_message, error) = self.thread.join()?;
	if read_at_least_one_message || exit_status.success() {
	Ok(())
	} else {
	Err(io::Error::new(io::ErrorKind::Other, format!(
	"Cargo watcher failed, the command produced no valid metadata (exit code: {exit_status:?}):\n{error}"
	)))
	}
	}

and finally, this PR appends it at the end of existing Flycheck error message

[lnicola]

r? @davidbarsky

Not sure if it matters, but we can probably do something like:

tracing::error!(%error, formatted_handle, "flycheck failed to run");

[davidbarsky]

r? @davidbarsky

Not sure if it matters, but we can probably do something like:

tracing::error!(%error, formatted_handle, "flycheck failed to run");

Yeah, this PR looks good to me (I don't think bors accepts commands from me? I've never tried), but reformat the expression like that is a nice bonus!

(It'd be neat if I could figure out how write that transform with SSR.)

[Veykril]

I don't think bors accepts commands from me? I've never tried)

It doesn't (at least not yet), but feel free to approve PRs via github nevertheless!

(It'd be neat if I could figure out how write that transform with SSR.)

I don't think SSR can interpolate from strings (changing the {} captures)

[Veykril]

@bors r+

[bors]

📌 Commit f7a66fd has been approved by Veykril

It is now in the queue for this repository.

[bors]

⌛ Testing commit f7a66fd with merge 657b33b...

[bors]

☀️ Test successful - checks-actions
Approved by: Veykril
Pushing 657b33b to master...