Inconsistent summary on error count with --message-format=json

[zjp-CN]

Problem

cargo check emits a good summary on error count, but with --message-format json, the count number is increased by 1 because it seems to include the error summary itself as a new error. This also influences summary count of clippy in the same way.

As for warning count, the former reports the count, but with json format, no count is reported.

Steps

Repoducible repo: https://github.com/os-checker/MRE-cargo-error-count

// src/main.rs
#![deny(warnings)]
fn main() {
    let a = 1;
}

$ cargo check
error: could not compile `cargo-error-count` (bin "cargo-error-count") due to 1 previous error

$ cargo check --message-format json
error: could not compile `cargo-error-count` (bin "cargo-error-count") due to 2 previous errors

Note: this inconsistency might be a bit different on warning report

# with no #![deny(warnings)]
$ cargo check
warning: `cargo-error-count` (bin "cargo-error-count") generated 1 warning

# with no #![deny(warnings)]
$ cargo check --message-format json
# no count reported

Possible Solution(s)

No response

Notes

No response

Version

cargo 1.82.0-nightly (0d8d22f83 2024-08-08)
release: 1.82.0-nightly
commit-hash: 0d8d22f83b066503f6b2b755925197e959e58b4f
commit-date: 2024-08-08
host: x86_64-unknown-linux-gnu
libgit2: 1.8.1 (sys:0.19.0 vendored)
libcurl: 8.9.0-DEV (sys:0.4.74+curl-8.9.0 vendored ssl:OpenSSL/3.3.1)
ssl: OpenSSL 3.3.1 4 Jun 2024
os: Ubuntu 22.4.0 (jammy) [64-bit]

[weihanglo]

The root cause is that Cargo skips counting when seeing these messages:

cargo/src/cargo/core/compiler/mod.rs

Lines 1798 to 1801 in b8a4f1b

	if msg.message.starts_with("aborting due to")
	|| msg.message.ends_with("warning emitted")
	|| msg.message.ends_with("warnings emitted")
	{

However, it doesn't do that here:

cargo/src/cargo/core/compiler/mod.rs

Lines 1880 to 1886 in b8a4f1b

	#[derive(serde::Deserialize)]
	struct CompilerMessage {
	level: String,
	}
	if let Ok(message) = serde_json::from_str::<CompilerMessage>(compiler_message.get()) {
	count_diagnostic(&message.level, options);
	}

@Muscraft had made a workable fix during RustConf last week. Basically duplicating the skipping logic. That seems to be an acceptable hack.

[yichi170]

@rustbot claim