codemirror-lang-icu-messageformat

ICU MessageFormat syntax support for CodeMirror 6.

ICU MessageFormat is the pattern syntax used for internationalized, pluralized, and gender/category-selected UI strings — widely used via intl-messageformat, formatjs, ICU4J/ICU4C, and many i18n libraries.

Installation

npm install @actualwave/codemirror-lang-icu-messageformat

Usage

import { EditorState } from "@codemirror/state"
import { EditorView } from "@codemirror/view"
import { icuMessageFormat } from "@actualwave/codemirror-lang-icu-messageformat"

const state = EditorState.create({
  doc: `You have {count, plural,
  =0 {no messages}
  one {# message}
  other {# messages}
}.`,
  extensions: [icuMessageFormat()],
})

const view = new EditorView({ state, parent: document.body })

API

icuMessageFormat()

Returns a LanguageSupport instance. This is the main extension to add to your editor.

icuMessageFormatLanguage

The LRLanguage instance for ICU MessageFormat. Use this when you need direct access to the language object, for example to add language-specific extensions via icuMessageFormatLanguage.data.of(...).

icuHighlighting

The highlight style prop source used by the parser. Exported for advanced use cases where you want to build a custom language configuration.

Features

• Literal message text, interleaved with {argument} placeholders
• Simple arguments: {name, number}, {name, date, short}, {name, time, ::HH:mm}, etc.
• Selector arguments with recursively nested sub-messages:
  • {name, plural, offset:1 =0 {...} one {...} other {...}}
  • {name, selectordinal, one {...} two {...} few {...} other {...}}
  • {name, select, male {...} female {...} other {...}}
• The # placeholder inside plural/selectordinal branches
• Quoted literal text ('{', '#', etc.) and the '' escaped-apostrophe sequence
• Positional ({0}) and named ({name}) argument references

Known v1 limitations

• # is tokenized uniformly everywhere rather than only inside plural/selectordinal branches (it's only meaningful there per the ICU spec, but treating it context-free keeps the grammar simple — same spirit as this project's other DSL grammars).
• Argument style text (e.g. a number/date skeleton) is treated as an opaque run of text rather than parsed into its own sub-grammar.

License

MIT