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fix(ops): correct error messages for cargo fix --broken-code #16681

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fix(ops): correct error messages for cargo fix --broken-code #16681

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b31857c
fix: update diagnostic server wording for failed fixes
raushan728 Mar 20, 2026
bf154e3
fix: refine termination logic when no fixes available with --broken-code
raushan728 Mar 20, 2026
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10 changes: 4 additions & 6 deletions src/cargo/ops/fix/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -789,12 +789,7 @@ pub fn fix_exec_rustc(gctx: &GlobalContext, lock_addr: &str) -> CargoResult<()>
}
}

// If there were any fixes, let the user know that there was a failure
// attempting to apply them, and to ask for a bug report.
//
// FIXME: The error message here is not correct with --broken-code.
// https://github.com/rust-lang/cargo/issues/10955
if fixes.files.is_empty() {
if fixes.files.is_empty() && !allow_broken_code {
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@epage epage Mar 18, 2026

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Multiple changes are being done at once in this commit. Please split up individual changes to better describe in their commit their intent and to make it clearer by more incremental test updates.

// No fixes were available. Display whatever errors happened.
emit_output(&fixes.last_output)?;
exit_with(fixes.last_output.status);
Expand All @@ -814,6 +809,7 @@ pub fn fix_exec_rustc(gctx: &GlobalContext, lock_addr: &str) -> CargoResult<()>
krate,
&fixes.last_output.stderr,
fixes.last_output.status,
allow_broken_code,
)?;
// Display the diagnostics that appeared at the start, before the
// fixes failed. This can help with diagnosing which suggestions
Expand Down Expand Up @@ -1171,6 +1167,7 @@ fn log_failed_fix(
krate: Option<String>,
stderr: &[u8],
status: ExitStatus,
allow_broken_code: bool,
) -> CargoResult<()> {
let stderr = str::from_utf8(stderr).context("failed to parse rustc stderr as utf-8")?;

Expand Down Expand Up @@ -1205,6 +1202,7 @@ fn log_failed_fix(
krate,
errors,
abnormal_exit,
allow_broken_code,
}
.post(gctx)?;

Expand Down
52 changes: 31 additions & 21 deletions src/cargo/util/diagnostic_server.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -43,6 +43,7 @@ pub enum Message {
krate: Option<String>,
errors: Vec<String>,
abnormal_exit: Option<String>,
allow_broken_code: bool,
},
ReplaceFailed {
file: String,
Expand Down Expand Up @@ -146,6 +147,7 @@ impl<'a> DiagnosticPrinter<'a> {
krate,
errors,
abnormal_exit,
allow_broken_code,
} => {
let to_crate = if let Some(ref krate) = *krate {
format!(" to crate `{krate}`",)
Expand All @@ -160,28 +162,36 @@ impl<'a> DiagnosticPrinter<'a> {
None
};

let report = &[
Level::ERROR
.secondary_title(format!("errors present after applying fixes{to_crate}"))
.elements(files.iter().map(|f| Origin::path(f)))
.elements(
cause_message
.into_iter()
.map(|err| Level::ERROR.with_name("cause").message(err)),
)
.elements(abnormal_exit.iter().map(|exit| {
Level::ERROR
.with_name("cause")
.message(format!("rustc exited abnormally: {exit}"))
})),
gen_please_report_this_bug_group(issue_link),
gen_suggest_broken_code_group(),
Group::with_title(
Level::NOTE.secondary_title("original diagnostics will follow:"),
),
];
let report = &[Level::ERROR
.secondary_title(format!("errors present after applying fixes{to_crate}"))
.elements(files.iter().map(|f| Origin::path(f)))
.elements(
cause_message
.into_iter()
.map(|err| Level::ERROR.with_name("cause").message(err)),
)
.elements(abnormal_exit.iter().map(|exit| {
Level::ERROR
.with_name("cause")
.message(format!("rustc exited abnormally: {exit}"))
}))];

let mut report = report.to_vec();

if *allow_broken_code {
report.push(Group::with_title(Level::WARNING.secondary_title(
"fixes were applied but the code still does not compile; partially-fixed code was saved due to `--broken-code`"
)));
} else {
report.push(gen_please_report_this_bug_group(issue_link));
report.push(gen_suggest_broken_code_group());
}

self.gctx.shell().print_report(report, false)?;
report.push(Group::with_title(
Level::NOTE.secondary_title("original diagnostics will follow:"),
));

self.gctx.shell().print_report(&report, false)?;
Ok(())
}
Message::EditionAlreadyEnabled { message, edition } => {
Expand Down
38 changes: 34 additions & 4 deletions tests/testsuite/fix.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1435,11 +1435,9 @@ fn fix_to_broken_code() {
= cause: thread 'main' ([..]) panicked at src/main.rs:23:29:
explicit panic
[NOTE] run with `RUST_BACKTRACE=1` environment variable to display a backtrace
[HELP] to report this as a bug, open an issue at https://github.com/rust-lang/rust/issues, quoting the full output of this command
[HELP] to possibly apply more fixes, pass in the `--broken-code` flag
[WARNING] fixes were applied but the code still does not compile; partially-fixed code was saved due to `--broken-code`
[NOTE] original diagnostics will follow:
...

"#]])
.run();

Expand Down Expand Up @@ -2381,6 +2379,38 @@ fn fix_in_rust_src() {
.with_status(101)
.with_stderr_data(str![[r#"
[CHECKING] foo v0.0.0 ([ROOT]/foo)
[ERROR] errors present after applying fixes to crate `foo`
--> [..]macros/mod.rs
::: lib.rs
= cause: error[E0308]: mismatched types
--> lib.rs:5:9
|
2 | / if true {
3 | | writeln!(w, "`;?` here ->")?;
4 | | } else {
5 | | writeln!(w, "but not here")
| | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `()`, found `Result<(), Error>`
6 | | }
| |_____- expected this to be `()`
|
= [NOTE] expected unit type `()`
found enum `Result<(), std::fmt::Error>`
= [NOTE] this error originates in the macro `writeln` (in Nightly builds, run with -Z macro-backtrace for more info)
[HELP] consider using a semicolon here
|
6 | };
| +
[HELP] you might have meant to return this value
|
5 | return writeln!(w, "but not here");
| ++++++ +
[HELP] use the `?` operator to extract the `Result<(), std::fmt::Error>` value, propagating a `Result::Err` value to the caller
--> [..]macros/mod.rs:670:58
|
67| $dst.write_fmt($crate::format_args_nl!($($arg)*))?
| +
[WARNING] fixes were applied but the code still does not compile; partially-fixed code was saved due to `--broken-code`
[NOTE] original diagnostics will follow:
error[E0308]: mismatched types
--> lib.rs:5:9
|
Expand All @@ -2404,7 +2434,7 @@ error[E0308]: mismatched types
5 | return writeln!(w, "but not here");
| ++++++ +
[HELP] use the `?` operator to extract the `Result<(), std::fmt::Error>` value, propagating a `Result::Err` value to the caller
--> [..]/lib/rustlib/src/rust/library/core/src/macros/mod.rs:670:58
--> [..]macros/mod.rs:670:58
|
67| $dst.write_fmt($crate::format_args_nl!($($arg)*))?
| +
Expand Down
8 changes: 6 additions & 2 deletions tests/testsuite/fix_n_times.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -439,6 +439,11 @@ fn broken_code_no_suggestions() {
},
str![[r#"
[CHECKING] foo v0.0.1 ([ROOT]/foo)
[ERROR] errors present after applying fixes to crate `foo`
--> src/lib.rs
= cause: rustc fix shim error count=1
[WARNING] fixes were applied but the code still does not compile; partially-fixed code was saved due to `--broken-code`
[NOTE] original diagnostics will follow:
rustc fix shim error count=1
[ERROR] could not compile `foo` (lib) due to 1 previous error

Expand All @@ -460,8 +465,7 @@ fn broken_code_one_suggestion() {
[ERROR] errors present after applying fixes to crate `foo`
--> src/lib.rs
= cause: rustc fix shim error count=2
[HELP] to report this as a bug, open an issue at https://github.com/rust-lang/rust/issues, quoting the full output of this command
[HELP] to possibly apply more fixes, pass in the `--broken-code` flag
[WARNING] fixes were applied but the code still does not compile; partially-fixed code was saved due to `--broken-code`
[NOTE] original diagnostics will follow:
rustc fix shim comment 1
rustc fix shim error count=2
Expand Down