i18n-string-coverage

Overview

Two coverage gaps this skill detects: hardcoded user-facing text not wrapped in the i18n function, and keys present in en.json but missing from a locale file (so the UI shows the raw key). It finds both via source scanning plus a translation-file diff.

When to use

• The product ships in 2+ locales.
• A bug report says "X appears in English in Y locale."
• Quarterly: scheduled coverage review.
• A new locale launches and the team needs the gap inventory.

How to use

1. Identify the i18n wrap function for the stack (Step 1 table).
2. Scan source for hardcoded user-facing text not wrapped in t() (Step 2).
3. Diff each locale file against the en source-of-truth for per-locale coverage % (Step 3).
4. Assemble the report: per-locale %, new untranslated strings, orphan keys (Step 4).
5. Wire the scan into a per-PR gate that fails on new untranslated strings (Step 5).
6. Flag RTL / bidi strings that need extra translator attention (Step 6).

Step 1 - Identify the i18n library

Per stack, the wrap function differs:

Configure per project.

Step 2 - Scan for untranslated strings

# Pattern: JSX/TSX text children that aren't wrapped
# (heuristic; refines per-codebase)
grep -rn -E '>[A-Z][a-z]+ ?[A-Za-z ]*<' src/components/ \
  | grep -v -E '\$?\{?t\(|i18n\.t\(|trans|formatMessage'

This catches the obvious cases - <button>Submit</button> - without false-positive on <button>{t('submit')}</button>.

For more comprehensive detection, language-specific tooling:

Step 3 - Diff translation files

# scripts/i18n-coverage.py
import json
from pathlib import Path

def flatten(d, prefix=''):
    for k, v in d.items():
        full = f'{prefix}.{k}' if prefix else k
        if isinstance(v, dict):
            yield from flatten(v, full)
        else:
            yield full

base_keys = set(flatten(json.loads(Path('locales/en.json').read_text())))  # source-of-truth

coverage = {}
for f in Path('locales').glob('*.json'):
    if f.stem == 'en': continue
    keys = set(flatten(json.loads(f.read_text())))
    covered = base_keys & keys
    coverage[f.stem] = {
        'missing': sorted(base_keys - keys),
        'extra_orphans': sorted(keys - base_keys),
        'pct': round(100 * len(covered) / len(base_keys), 1),
    }

print(json.dumps(coverage, indent=2))

Step 4 - Report

Assemble per-locale coverage %, the new untranslated source strings (file, line, string, suggested key), and orphan keys (present in a locale file but not in source - deletion candidates). Full fill-in template: references/coverage-report.md.

Step 5 - PR gate

- name: i18n coverage check
  if: github.event_name == 'pull_request'
  run: |
    NEW_UNWRAPPED=$(./scripts/i18n-scan.sh)
    if [ -n "$NEW_UNWRAPPED" ]; then
      echo "::error::New untranslated strings found:"
      echo "$NEW_UNWRAPPED"
      exit 1
    fi

For new locales without 100% coverage, gate is informational, not blocking - the gap is tracked, not blocked.

Step 6 - Bilingual / RTL flagging

For RTL languages (Arabic, Hebrew, Persian, Urdu - per w3-rtl (opens in new window)), the report also flags:

• Strings that include hardcoded LTR/RTL marker characters.
• Strings with embedded HTML (often direction-sensitive).
• Strings combining RTL and LTR text (need bidi handling).

These need extra translator attention even when "translated" - character-by-character translation may not render correctly without bidi guidance.

Worked example

A PR adds a promo banner to checkout. The scan (Step 2) flags <button>Apply your discount</button> in src/checkout/PromoBanner.tsx:18 - the text is not wrapped in t(). The translation-file diff (Step 3) reports ja at 60% coverage (218 keys missing) against 542 en keys.

The PR gate (Step 5) blocks on the newly unwrapped string; the ja gap stays informational, not blocking. The developer wraps the text as t('checkout.promo.banner_cta'), adds the key to all five locale files, and re-runs. The scan reports zero new untranslated strings and the gate passes.

Anti-patterns

Limitations

• Heuristic scanning has gaps. Dynamically-constructed strings (e.g., t(dynamicKey)) miss; manual review required.
• Translator quality not addressed. "Translated" doesn't mean "good translation"; pair with linguistic review.
• Per-language differences in pluralization, gender, etc. Some i18n libraries handle these well (ICU MessageFormat); others poorly. Coverage % doesn't reflect quality.

References

• w3rtl (opens in new window) - W3C on dir attribute + RTL languages.
• pseudo-localization-runner - sibling: layout-level i18n testing.
• rtl-rendering-tester - RTL-specific rendering verification.
• locale-format-validator - date / number / currency format verification.