swc-project/swc · info

We don't care about this file

Error message

We don't care about this file

What it means

Not a real failure: when dbg-swc runs as a creduce interestingness test (CREDUCE_MODE=SIZE), SIZE mode compares SWC's minified output length against terser's; if SWC's output is not larger, the file cannot expose a size regression, so the run bails with this sentinel to exit non-zero, which creduce interprets as 'not interesting'. The complementary case (SWC output strictly larger) returns Ok and exits 0. Treat this message as a filter signal, never as a bug.

Source

Thrown at crates/dbg-swc/src/main.rs:91

                    HANDLER.set(handler, || {
                        //
                        let input = PathBuf::from(
                            env::var(CREDUCE_INPUT_ENV_VAR)
                                .expect("creduce is invoked without the name of input file"),
                        );

                        if mode == "SIZE" {
                            let m = get_minified(cm.clone(), &input, true, true)?;

                            let swc_output = print_js(cm.clone(), &m.module, true)?;

                            let terser_output = get_terser_output(&input, true, true)?;
                            if swc_output.trim().len() > terser_output.trim().len() {
                                // It's interesting, as our output is larger than terser's.
                                return Ok(());
                            }

                            bail!("We don't care about this file")
                        } else if mode == "SEMANTICS" {
                            let m = get_minified(cm.clone(), &input, true, false)?;

                            let swc_output = print_js(cm.clone(), &m.module, true)?;

                            let terser_output = get_terser_output(&input, true, false)?;

                            if swc_output.trim() == terser_output.trim() {
                                bail!("We don't care about this file")
                            }

                            // It's interesting, as our output may have a bug

                            Ok(())
                        } else {
                            unreachable!("Unknown mode `{}`", mode)
                        }
                    })

View on GitHub (pinned to 5176682b65)

Solutions

1. No fix needed under creduce: non-zero exit for uninteresting files is the designed contract
2. If you see it outside creduce, unset CREDUCE_MODE (and CREDUCE_INPUT) from the environment
3. Remember the success condition in SIZE mode: exit 0 only when swc output is strictly larger than terser's

Example fix

# before: sentinel mistaken for a crash in scripts
run_dbg() { dbg-swc es minifier ... ; }

# after: treat this exact message as 'skip', not failure
if out=$(dbg-swc es minifier ... 2>&1); then exit 0; fi
case "$out" in
  *"We don't care about this file"*) exit 1 ;; # not interesting
  *) exit 2 ;;                                   # real failure
esac

# creduce interestingness wrapper: distinguish the skip sentinel from real crashes
if out=$(dbg-swc es minifier ... 2>&1); then
  exit 0                            # interesting: swc output larger than terser's
fi
case "$out" in
  *"We don't care about this file"*) exit 1 ;;  # not interesting - by design
  *) exit 2 ;;                                   # real failure - inspect output
esac

When it happens

Trigger: CREDUCE_MODE=SIZE set (creduce invokes dbg-swc per candidate) and the candidate's swc-minified output length is less than or equal to the terser output length; the bail is the intended skip signal.

Common situations: Reading creduce logs and mistaking the sentinel for a crash; accidentally exporting CREDUCE_MODE in the environment so normal dbg-swc runs take the creduce path; debugging why most candidate files 'error out' during a reduction session (by design).

Related errors

• `npm run build` failed
• Infinite loop detected (current pass = {}) {}
• failed to parse `global_defs.{k}` of minifier options: {err:
• Value of `global_defs.{k}` must be a string literal:
• failed to parse `pure_funcs` of minifier options: {err:?}

AI-assisted analysis of swc-project/swc@5176682b65 (2026-08-17). Data as JSON: /api/errors/ad4f9e37dd17aa72. Report an issue: GitHub.