Write summary messages to stderr when fixing via stdin (instead of om…

…itting them) (#7838)

Previously we just omitted diagnostic summaries when using `--fix` or
`--diff` with a stdin file. Now, we still write the summaries to stderr
instead of the main writer (which is generally stdout but could be
changed by `--output-file`).

crates/ruff_cli/src/lib.rs

@@ -208,6 +208,7 @@ pub fn check(args: CheckCommand, log_level: LogLevel) -> Result<ExitStatus> {
  }
  _ => Box::new(BufWriter::new(io::stdout())),
  };
+ let stderr_writer = Box::new(BufWriter::new(io::stderr()));
 
  if cli.show_settings {
  commands::show_settings::show_settings(
@@ -392,15 +393,18 @@ pub fn check(args: CheckCommand, log_level: LogLevel) -> Result<ExitStatus> {
  )?
  };
 
- // Always try to print violations (the printer itself may suppress output),
- // unless we're writing fixes via stdin (in which case, the transformed
- // source code goes to stdout).
- if !(is_stdin && matches!(fix_mode, FixMode::Apply | FixMode::Diff)) {
- if cli.statistics {
- printer.write_statistics(&diagnostics, &mut writer)?;
- } else {
- printer.write_once(&diagnostics, &mut writer)?;
- }
+ // Always try to print violations (though the printer itself may suppress output)
+ // If we're writing fixes via stdin, the transformed source code goes to the writer
+ // so send the summary to stderr instead
+ let mut summary_writer = if is_stdin && matches!(fix_mode, FixMode::Apply | FixMode::Diff) {
+ stderr_writer
+ } else {
+ writer
+ };
+ if cli.statistics {
+ printer.write_statistics(&diagnostics, &mut summary_writer)?;
+ } else {
+ printer.write_once(&diagnostics, &mut summary_writer)?;
  }
 
  if !cli.exit_zero {

crates/ruff_cli/tests/integration_test.rs

@@ -150,6 +150,7 @@ fn stdin_fix_py() {
  print(sys.version)
 
  ----- stderr -----
+ Found 1 error (1 fixed, 0 remaining).
  "###);
 }
 
@@ -317,6 +318,7 @@ fn stdin_fix_jupyter() {
  "nbformat_minor": 5
  }
  ----- stderr -----
+ Found 2 errors (2 fixed, 0 remaining).
  "###);
 }
 
@@ -336,6 +338,8 @@ fn stdin_fix_when_not_fixable_should_still_print_contents() {
  print(sys.version)
 
  ----- stderr -----
+ -:3:4: F634 If test is a tuple, which is always `True`
+ Found 2 errors (1 fixed, 1 remaining).
  "###);
 }
 
@@ -961,6 +965,9 @@ fn fix_applies_safe_fixes_by_default() {
  print('foo')
 
  ----- stderr -----
+ -:1:14: F601 Dictionary key literal `'a'` repeated
+ Found 2 errors (1 fixed, 1 remaining).
+ 1 hidden fix can be enabled with the `--unsafe-fixes` option.
  "###);
 }
 
@@ -988,6 +995,7 @@ fn fix_applies_unsafe_fixes_with_opt_in() {
  print('foo')
 
  ----- stderr -----
+ Found 2 errors (2 fixed, 0 remaining).
  "###);
 }
 
@@ -1014,6 +1022,7 @@ fn fix_only_flag_applies_safe_fixes_by_default() {
  print('foo')
 
  ----- stderr -----
+ Fixed 1 error.
  "###);
 }
 
@@ -1041,6 +1050,7 @@ fn fix_only_flag_applies_unsafe_fixes_with_opt_in() {
  print('foo')
 
  ----- stderr -----
+ Fixed 2 errors.
  "###);
 }
 
@@ -1070,6 +1080,7 @@ fn diff_shows_safe_fixes_by_default() {
 
 
  ----- stderr -----
+ Would fix 1 error.
  "###
  );
 }
@@ -1102,6 +1113,7 @@ fn diff_shows_unsafe_fixes_with_opt_in() {
 
 
  ----- stderr -----
+ Would fix 2 errors.
  "###
  );
 }