@mozilla/l10n

This is a library of JavaScript tools and utilities for working with localization files, primarily built for internal use at Mozilla.

It's being bootstrapped to fulfil the needs of the Pontoon frontend, and to match the behaviour of the Python moz.l10n library.

The data structures used by the library are defined by a JSON Schema.

The library currently supports the following message pattern formats:

• android: Android string resources
• fluent: Fluent (without internal selectors)
• mf2: MessageFormat 2.0
• plain: Patterns without placeholders (used in multiple resource formats)
• webext: WebExtensions (messages.json)
• xliff: XLIFF 1.2, including XCode customizations

The tooling for android and xliff depends on DOMParser, XMLSerializer, and related classes which are available in browser environments. The parser for fluent depends on the @fluent/syntax package, and the parser for mf2 depends on the messageformat package.

API

parsePattern()

import { ParseError, parsePattern } from '@mozilla/l10n'

function parsePattern(
  format: 'android' | 'fluent' | 'mf2' | 'plain' | 'webext' | 'xliff',
  src: string,
  baseMsg?: Message,
  onError?: (error: ParseError) => void
): Pattern

class ParseError extends Error {
  range?: [number, number]  // Set for fluent, mf2, and webext errors
}

Parse the string representation of a single flat message pattern into a data structure (JSON Schema).

The baseMsg is required by webext for named placeholders.

If onError is undefined, errors are thrown.

serializePattern()

import { SerializeError, serializePattern } from '@mozilla/l10n'

function serializePattern(
  format: 'android' | 'fluent' | 'mf2' | 'plain' | 'webext' | 'xliff',
  pattern: Pattern,
  onError?: (error: SerializeError) => void
): string

class SerializeError extends Error {
  pos?: number  // Set for fluent, plain, and webext errors
}

Serialize the data representation of a single flat message pattern into a string

If onError is undefined, errors are thrown.

Types

import type {
  Message,
  PatternMessage,
  SelectMessage,
  Pattern,
  Expression,
  Markup
} from '@mozilla/l10n'

type Message = Pattern | PatternMessage | SelectMessage
type Pattern = (string | Expression | Markup)[]