العربية

Flutter L10n Watch

A translation health check for Flutter projects: missing keys, broken placeholders, Arabic plurals, unused and undefined keys, hardcoded strings and RTL smells, in one command.

English summary. l10n_watch is a zero-setup Dart CLI that audits the translations of a Flutter app. It detects the setup on its own (easy_localization JSON with nested keys and the generated LocaleKeys class, gen_l10n / intl_utils ARB with ICU messages, or plain JSON maps), then reports: keys missing per locale (and keys only some locales have), empty values, values identical to the base language, placeholder mismatches ({}, {name}, ICU arguments), plural forms each language needs (Arabic: zero/one/two/few/many/other), malformed ICU, ARB placeholder metadata out of sync, keys used in code but not defined, keys defined but never used (with 'status_$x'.tr() treated as a possibly used prefix), translations long enough to overflow, hardcoded strings in Text(...) / hintText: / tooltip: and friends, and RTL smells such as EdgeInsets.only(left:) or Alignment.centerLeft. check exits 1 on errors so it fits CI; report prints text, Markdown, JSON or GitHub annotations. Everything is configurable in l10n_watch.yaml. Pure Dart, no Flutter SDK needed to run it, no network.

A command-line tool that checks all the translations of a Flutter project in one command: what is missing, what was never translated, which placeholder got broken, which Arabic plural forms are missing, which text is hardcoded in the code, and what will break the screen when the language is right-to-left.

✨ What it checks

Check	id	Default
🔑 Keys missing from a locale compared with the base locale	missing_translation	error
➕ Keys present in a locale but not in the base locale	extra_translation	warning
⬜ Empty values	empty_value	warning
🪞 Value identical to the English one (probably forgotten) or marked TODO:	untranslated	warning
🧩 Placeholders differ: {}, {name} and ICU	placeholder_mismatch	error
🔢 Plural forms missing for the language (Arabic needs zero/one/two/few/many/other)	plural_forms	warning
💥 Broken ICU message, a plural without other, or ICU inside easy_localization JSON	invalid_message	error
🏷 @key.placeholders in the ARB does not match the message	arb_metadata	warning
❓ Key used in the code but not defined	undefined_key	error
🗑 Key defined but never used	unused_key	warning
🌀 Key built at runtime ('status_$x'.tr())	dynamic_key	info
📏 Translation much longer than the source (overflow risk)	length_risk	info
✍️ Text written in the code instead of coming from the translations	hardcoded_string	warning
↔️ Things that break in RTL	rtl_smell	info

🧠 It understands the project on its own

• easy_localization: finds the translations folder from EasyLocalization(path: ...) in the code, from assets in pubspec.yaml, or from the well-known locations (assets/translations, assets/lang, …). It understands nested keys (cart.title), plural objects (one/other), links (@:key), and the base locale from fallbackLocale. It counts usage from 'key'.tr(), tr('key'), context.tr('key'), 'key'.plural(n), Text('key').tr() and (cond ? 'a' : 'b').tr(), and from LocaleKeys.foo_bar: it reads the generated LocaleKeys class if it exists, and if it does not, it maps foo.bar and foo_bar to the same name the way the generator does.
• gen_l10n (ARB): reads l10n.yaml (arb-dir, template-arb-file, output-class and use-escaping), and understands full ICU: placeholders, plural, select and nesting. Usage is counted from AppLocalizations.of(context)!.key, context.l10n.key, S.of(context).key and S.current.key, and from any variable created from them (final t = AppLocalizations.of(context)!; or a field of type AppLocalizations). intl_utils (flutter_intl in pubspec, class S) works too.
• Plain JSON for any other library: format: json, with placeholders matched by the regex you choose.
• Generated files (*.g.dart, generated/, any file starting with "GENERATED / DO NOT EDIT", and the generated localizations class) are not counted for usage or for hardcoded strings.

🚀 Installation

dart pub global activate flutter_l10n_watch
cd my_flutter_app
l10n_watch check

Or inside the project as a dev dependency:

dev_dependencies:
  flutter_l10n_watch: ^0.1.0

dart run flutter_l10n_watch:l10n_watch check

🕹 Commands

l10n_watch check                        # all checks, exit 1 if there is an error
l10n_watch check --fail-on warning      # make warnings fail the CI too
l10n_watch check --checks missing_translation,placeholder_mismatch
l10n_watch report --format markdown -o l10n.md   # for a PR comment or job summary
l10n_watch report --format json                  # for any other tool
l10n_watch report --format github                # annotations on the PR lines
l10n_watch report --all                          # without truncating long lists
l10n_watch fix --sort --dry-run                  # shows what it would change without writing
l10n_watch fix --sort                            # sorts the keys in every file
l10n_watch fix --add-missing                     # adds missing keys with the base value + "TODO: "
l10n_watch init                                  # writes an l10n_watch.yaml with every setting

fix does nothing without a flag, and never touches a file it cannot read. The values it adds are prefixed with TODO: so the untranslated check keeps catching them until someone translates them.

🖥 What the report looks like

l10n_watch 0.1.0 · easy_localization · assets/translations · base en · 3 locales · 16 keys · 2 Dart files

✖ Missing translations (1 error) [missing_translation]
  ar: missing "cart.checkout"

✖ Placeholder mismatch (2 errors) [placeholder_mismatch]
  ar: "greeting" has {user}, en has {name}
  ar: "items_count" has {}, en has {}×2

⚠ Plural forms missing for the language (1 warning) [plural_forms]
  ar: "apples" plural lacks zero, two, few, many (ar uses zero/one/two/few/many/other)

✖ Keys used in code but not defined (2 errors) [undefined_key]
  lib/home.dart:29  "missing_key" is used ('key'.tr()) but not defined in en
  lib/home.dart:30  "removed_key" is used (LocaleKeys.removed_key) but not defined in en

ℹ Dynamic keys (possibly used) (3 infos) [dynamic_key]
  lib/home.dart:27  "'status_$status'" → prefix "status_" matches 2 keys (2 otherwise unused)

⚠ Hardcoded user-facing strings (5 warnings) [hardcoded_string]
  top files:
       5  lib/home.dart
  lib/home.dart:35  "Hardcoded hello" in Text()
  lib/home.dart:39  "Type here" in hintText:

ℹ RTL smells (6 infos) [rtl_smell]
     1  EdgeInsets.only(left/right) → EdgeInsetsDirectional.only(start/end)
     1  Alignment.centerLeft → AlignmentDirectional.centerStart
     1  Positioned(left/right) → PositionedDirectional(start/end)

✖ 8 errors · 14 warnings · 10 info

⚙️ Configuration (l10n_watch.yaml)

Everything is optional. Without the file the tool runs with the defaults.

format: auto                  # auto | easy_localization | arb | json
translations_dir: assets/translations
base_locale: en
source_dirs: [lib]
exclude: ['lib/legacy/**']    # on top of the defaults (*.g.dart, generated/, ...)
ignore_keys: ['^debug_']      # regex, ignored by every check
locale_keys_class: LocaleKeys
tr_functions: [tr, plural, trExists]
arb_accessors: ['context.loc']        # if you have a shortcut other than context.l10n
placeholder_pattern: '\{\{\s*(\w*)\s*\}\}'   # for format: json only

untranslated:
  min_letters: 3              # shorter than this (OK, ID, 1st) is not counted
  allow: [Visa, PayPal, WhatsApp]     # words that stay the same in every language
  ignore_keys: ['^country_']
  todo_marker: 'TODO: '

length:
  ratio: 1.6
  min_chars: 20

hardcoded:
  widgets: [Text, SelectableText, AutoSizeText]
  named_args: [hintText, labelText, helperText, errorText, tooltip, TextSpan.text, Tooltip.message]
  ignore: ['^Lorem']

plural_rules:                 # on top of the default CLDR table
  fr: [one, many, other]

severity:                     # error | warning | info | off
  unused_key: error
  rtl_smell: off

fail_on: error                # check returns 1 from this level and above

A line containing // l10n-ignore is not reported by hardcoded_string or rtl_smell.

🤖 In CI

- run: dart pub global activate flutter_l10n_watch
- run: l10n_watch report --format github      # annotations on the PR
- run: l10n_watch report --format markdown >> "$GITHUB_STEP_SUMMARY"
- run: l10n_watch check                       # fails the job if there is an error

exit code	Meaning
0	Nothing reached fail_on
1	There are findings that reached fail_on (check only)
2	Invalid configuration, or the translation files could not be found

❓ FAQ

Why is a key reported as unused when I am sure it is used? Most likely the key is built at runtime from a variable (tr(item.titleKey)). Those cases show up in dynamic_key with their location in the code, so if you see a line there doing that, add the keys to ignore_keys. If the key is written as a string anywhere in the code (even in a map or a const list) it counts as used.

How is 'status_$x'.tr() handled? The constant part (status_) becomes a prefix, and every key starting with it is reported as "possibly used" in dynamic_key instead of unused_key.

English only needs one and other, so why does Arabic get a warning? Arabic has six plural forms in CLDR. If two is missing, for example, "٢ رسالة" ("2 messages") will be shown with the other form, which is grammatically wrong. =0, =1 and =2 in ICU count as zero, one and two.

A word like "Email" or the brand name is reported as untranslated. Add it to untranslated.allow. Words shorter than 3 letters, numbers, links and emails are not counted in the first place. And if the locale is a regional variant of the base language (en_GB with en), it is not checked.

JSON with {count, plural, ...} in easy_localization? easy_localization does not understand ICU, so the sentence is shown to the user as is. That is why it is reported as invalid_message; the fix is a plural object ({"one": "...", "other": "..."}) with .plural().

Can fix break the files? It writes valid JSON with the same indentation, keeps the trailing newline, and does nothing if any file cannot be read. What changes: escapes like é are written as the plain character. Try --dry-run first.

⚖️ Limitations

• It is not a full Dart parser: it reads the code with a lexer that understands strings, comments and interpolation, and the rest is regex. Very unusual usage patterns may slip past it (and the key is then reported as unused).
• Any string in the code that equals a key name makes that key "used", so the unused count may be lower than the real one (safer than telling you to delete something that is used).
• In ARB, any .name after a dot that equals a key name counts as a usage. A key named title, for example, will most likely look used.
• easy_localization: one JSON file per locale only (not a folder per locale, nor CSV/YAML).
• hardcoded_string looks at the first argument of Text and the types you configure, and at the known named args only. A string stored in a variable and displayed later is not caught.
• length_risk compares character counts, not the real width on screen.
• The plural table inside the tool is a condensed CLDR table for integers, and you can adjust it with plural_rules.

🛠 Development

dart pub get
dart format --output=none --set-exit-if-changed .
dart analyze --fatal-infos
dart test
dart run bin/l10n_watch.dart check -p test/fixtures/easy_app

🏗 Project structure

File	Role
bin/l10n_watch.dart	executable
lib/src/cli.dart	commands, options, exit codes
lib/src/config.dart	l10n_watch.yaml parsing and defaults (incl. CLDR plural table)
lib/src/project.dart	setup detection, locale files, Dart sources
lib/src/catalog.dart	JSON / ARB loaders, nested keys, plural and gender groups
lib/src/message.dart	{} / {name} placeholders, links and a small ICU parser
lib/src/dart_source.dart	Dart lexer: string literals, comments, interpolation, brackets
lib/src/usage.dart	key references: tr, LocaleKeys, AppLocalizations, dynamic keys
lib/src/checks/	catalog checks and code checks
lib/src/report/reporters.dart	text, Markdown, JSON and GitHub output
lib/src/fixer.dart	fix --sort / --add-missing
test/fixtures/	an easy_localization app and a gen_l10n app with one problem per check

📄 License

MIT

👤 Author

Youssef Belal Zakaria · GitHub @youssef336

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