What causes "argument --verbose / -v already set\n" in nodejs/node?

argument --verbose / -v already set\n

Error message

argument --verbose / -v already set\n

What it means

`-v`/`--verbose` enables verbose output. Unlike some tools, brotli does not increase verbosity with repeats; the parser rejects a second `-v`.

Source

Thrown at deps/brotli/c/tools/brotli.c:406

        } else if (c == 's') {
          if (squash_set) {
            fprintf(stderr, "argument --squash / -s already set\n");
            return COMMAND_INVALID;
          }
          squash_set = BROTLI_TRUE;
          params->reject_uncompressible = BROTLI_TRUE;
          continue;
        } else if (c == 't') {
          if (command_set) {
            fprintf(stderr, "command already set when parsing -t\n");
            return COMMAND_INVALID;
          }
          command_set = BROTLI_TRUE;
          command = COMMAND_TEST_INTEGRITY;
          continue;
        } else if (c == 'v') {
          if (params->verbosity > 0) {
            fprintf(stderr, "argument --verbose / -v already set\n");
            return COMMAND_INVALID;
          }
          params->verbosity = 1;
          continue;
        } else if (c == 'K') {
          if (concatenated_set) {
            fprintf(stderr, "argument -K / --concatenated already set\n");
            return COMMAND_INVALID;
          }
          concatenated_set = BROTLI_TRUE;
          params->allow_concatenated = BROTLI_TRUE;
          continue;
        } else if (c == 'V') {
          /* Don't parse further. */
          return COMMAND_VERSION;
        } else if (c == 'Z') {
          if (quality_set) {
            fprintf(stderr, "quality already set\n");

View on GitHub (pinned to 1b2de5e052)

Solutions

Pass `-v` exactly once.
Remove the duplicate from your alias or stacked flags.

Example fix

// before
brotli -vv file        # expecting extra verbosity
// after
brotli -v file         # verbose once

Defensive patterns

Strategy: validation

Validate before calling

assert sum(1 for a in argv if a in ('-v','--verbose') or (a.startswith('-') and not a.startswith('--') and 'v' in a)) <= 1

Prevention

Remember brotli has a single verbose level; one -v is enough.
Do not stack -v expecting levels.

When it happens

Trigger: Passing `-v` twice: `brotli -v -v file` or coalesced `brotli -vv file`.

Common situations: Users expecting `-vv` to mean 'more verbose' (it does not here); alias + explicit duplicate.

Related errors

AI-assisted analysis of nodejs/node@1b2de5e052 (2026-08-13). Data as JSON: /api/errors/a278600c2436de79. Report an issue: GitHub.