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fix(js): throw error when unsupported language is passed to CLI via -l / --lang - #1491

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tushuhei merged 2 commits into
google:mainfrom
codeXsidd:feat/issue-1490-cli-invalid-lang-error
Nov 4, 2026
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fix(js): throw error when unsupported language is passed to CLI via -l / --lang#1491
tushuhei merged 2 commits into
google:mainfrom
codeXsidd:feat/issue-1490-cli-invalid-lang-error

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@codeXsidd codeXsidd commented Nov 2, 2026

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Summary

When an unsupported language code is passed to the JavaScript CLI using -l or --lang, throw an explicit error with the list of available languages instead of silently falling back to the Japanese parser.

Problem

In javascript/src/cli.ts, parser resolution was implemented as:

  const parser = model
    ? loadCustomParser(model)
    : lang && defaultParsers.has(lang)
      ? defaultParsers.get(lang)!
      : loadDefaultJapaneseParser();

If a caller supplied an unknown language (such as budoux -l fr "Bonjour"), the condition lang && defaultParsers.has(lang) evaluated to false, causing the CLI to silently default to loadDefaultJapaneseParser(). This resulted in unexpected Japanese-model segmentation instead of informing the user that the language was not recognized. In contrast, the Python CLI validates language options and produces a clear error.

Solution

  • Added a check in javascript/src/cli.ts: if lang is provided (and model is not overriding), verify defaultParsers.has(lang). If not found, throw an Error stating that the language is not supported and listing available supported languages.
  • Added unit tests for both -l and --lang with unsupported language inputs in javascript/src/tests/cli_test.ts.

Testing

  • Unit tests: npx vitest run passed across all 6 test suites (166 tests passed).
  • CLI version check: node ./scripts/check-cli-version.js passed.
  • Linting / formatting: npx biome check src/cli.ts src/tests/cli_test.ts passed with 0 errors.

Related Issue

Closes #1490

tushuhei
tushuhei reviewed Nov 3, 2026
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@tushuhei tushuhei left a comment

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Thanks for your PR!

  1. Rather than adding an empty if (model) {} branch and falling back to loadDefaultJapaneseParser() (which also lets -l "" silently fall back to Japanese and instantiates the ja parser twice), please set 'ja' as the default value on .option('-l, --lang <str>', ..., 'ja') and resolve parser in a single lookup:
  .option(
    '-l, --lang <str>',
    `language model to use. -m and --model will be prioritized if any.\navailable languages: ${[
      ...defaultParsers.keys(),
    ].join(', ')}`,
    'ja'
  )
  const {lang, model, delim, sep, html} = options as {
    html: boolean;
    delim: string;
    sep: string;
    model?: string;
    lang: string;
  };
  const {args} = program;

  const parser =
    model !== undefined ? loadCustomParser(model) : defaultParsers.get(lang);
  if (!parser) {
    throw new Error(
      `'${lang}' is not supported. Available languages: ${[
        ...defaultParsers.keys(),
      ].join(', ')}`
    );
  }

(You can also remove the unused loadDefaultJapaneseParser import.)

  1. In javascript/src/tests/cli_test.ts, please avoid carrying over the stab typo (e.g., inline expect(() => cli(argv)).toThrowError(...)) and assert the full expected error message including [...loadDefaultParsers().keys()].join(', ').

@codeXsidd
fix(js): address reviewer feedback - set ja as default lang, remove e…
d40548f 
…mpty model branch, assert full error message in tests
@codeXsidd

codeXsidd commented Nov 3, 2026

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Thank you for the review @tushuhei! I've addressed both points:

  1. Set 'ja' as the default value directly on .option('-l, --lang ', ..., 'ja') and resolved the parser in a single lookup: const parser = model !== undefined ? loadCustomParser(model) : defaultParsers.get(lang). Removed the now-unused loadDefaultJapaneseParser import.
  2. Removed the stab typo variable and updated both error-throwing tests to use �xpect(() => cli(argv)).toThrowError(...) with the full expected error message including [...loadDefaultParsers().keys()].join(', ').

All 166 tests pass and biome check reports 0 errors.

@codeXsidd
codeXsidd requested a review from tushuhei November 3, 2026 14:59
@tushuhei
tushuhei merged commit 197046c into google:main Nov 4, 2026
22 checks passed
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fix(js): throw error when unsupported language is passed to CLI via -l / --lang

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