Internationalization (i18n) in Fabric

Fabric supports multiple languages through its internationalization system. The system automatically detects your preferred language from environment variables and provides localized messages.

How Locale Detection Works

Fabric follows POSIX standards for locale detection with the following priority order:

1. Explicit language flag: --language or -g (highest priority)
2. LC_ALL: Complete locale override environment variable
3. LC_MESSAGES: Messages-specific locale environment variable
4. LANG: General locale environment variable
5. Default fallback: English (en) if none are set or valid

Examples

# Use explicit language flag
fabric --language es --pattern summarize

# Use LC_ALL environment variable
LC_ALL=fr_FR.UTF-8 fabric --pattern summarize

# Use LANG environment variable
LANG=de_DE.UTF-8 fabric --pattern summarize

# Multiple environment variables (LC_ALL takes priority)
LC_ALL=es_ES.UTF-8 LANG=fr_FR.UTF-8 fabric --pattern summarize
# Uses Spanish (es_ES) because LC_ALL has higher priority

Supported Locale Formats

The system automatically normalizes various locale formats:

• en_US.UTF-8 → en-US
• fr_FR@euro → fr-FR
• zh_CN.GB2312 → zh-CN
• de_DE.UTF-8@traditional → de-DE

Special cases:

• C or POSIX → treated as invalid, falls back to English

Translation File Locations

Translations are loaded from multiple sources in this order:

1. Embedded files (highest priority): Compiled into the binary

   • Location: internal/i18n/locales/*.json
   • Always available, no download required

2. User config directory: Downloaded on demand

   • Location: ~/.config/fabric/locales/
   • Downloaded from GitHub when needed

3. GitHub repository: Source for downloads

   • URL: https://raw.githubusercontent.com/danielmiessler/Fabric/main/internal/i18n/locales/

Currently Supported Languages

• English (en): Default language, always available
• Spanish (es): Available in embedded files

Adding New Languages

To add support for a new language:

1. Create a new JSON file: internal/i18n/locales/{lang}.json

2. Add translations in the format:

   jsonCopy

   {
     "message_id": "localized message text"
   }
   

3. Rebuild Fabric to embed the new translations

Translation File Format

Translation files use JSON format with message IDs as keys:

{
  "html_readability_error": "use original input, because can't apply html readability"
}

Spanish example:

{
  "html_readability_error": "usa la entrada original, porque no se puede aplicar la legibilidad de html"
}

Error Handling

The i18n system is designed to be robust:

• Download failures: Non-fatal, falls back to embedded translations
• Invalid locales: Skipped, next priority locale used
• Missing translations: Falls back to English
• Missing files: Uses embedded defaults

Error messages are logged to stderr but don't prevent operation.

Environment Variable Examples

Common Unix Locale Settings

# Set system-wide locale
export LANG=en_US.UTF-8

# Override all locale categories
export LC_ALL=fr_FR.UTF-8

# Set only message locale (for this session)
LC_MESSAGES=es_ES.UTF-8 fabric --pattern summarize

# Check current locale settings
locale

Testing Locale Detection

You can test locale detection without changing your system settings:

# Test with French
LC_ALL=fr_FR.UTF-8 fabric --version

# Test with Spanish (if available)
LC_ALL=es_ES.UTF-8 fabric --version

# Test with German (will download if available)
LC_ALL=de_DE.UTF-8 fabric --version

Troubleshooting

"i18n download failed" messages

This is normal when requesting a language not yet available. The system will fall back to English.

Locale not detected

Check your environment variables:

echo $LC_ALL
echo $LC_MESSAGES
echo $LANG

Ensure they're in a valid format like en_US.UTF-8 or fr_FR.

Wrong language used

Remember the priority order:

1. --language flag overrides everything
2. LC_ALL overrides LC_MESSAGES and LANG
3. LC_MESSAGES overrides LANG

Implementation Details

The locale detection system:

• Uses golang.org/x/text/language for parsing and validation
• Follows BCP 47 language tag standards
• Implements POSIX locale environment variable precedence
• Provides comprehensive test coverage
• Handles edge cases gracefully

For developers working on the codebase, see the implementation in:

• internal/i18n/locale.go: Locale detection logic
• internal/i18n/i18n.go: Main i18n initialization
• internal/i18n/locale_test.go: Test suite