MF2 editor extensions

Editor tooling for ICU MessageFormat 2 (MF2) messages, maintained as a sibling of the localize Elixir library.

One grammar, several editor front-ends. Where the editor supports tree-sitter, it uses the shared tree-sitter-mf2/ grammar directly — same parse tree, same capture names, uniform highlighting across editors. Where the editor only supports regex grammars (VS Code TextMate, classic Vim), a separate per-editor implementation covers the same token classes.

Layout

Folder	Editor(s)	Parser	Elixir ~M sigil injection
tree-sitter-mf2/	Source of truth grammar (shared)	tree-sitter	—
zed-mf2/	Zed	tree-sitter	✅
nvim-mf2/	Neovim via nvim-treesitter	tree-sitter	✅
helix-mf2/	Helix	tree-sitter	✅
emacs-mf2/	Emacs 29+ via treesit.el	tree-sitter	✅
vscode-mf2/	Visual Studio Code	TextMate regex	✅
vim-mf2/	Classic Vim	Vim regex	—

Elixir ~M sigil injection

The Localize library provides a ~M sigil for compile-time-validated MF2 messages. Every extension in this repo that supports injection will switch grammars inside ~M"...", ~M"""...""", ~M(...), and the lowercase ~m variants, so the inner text is highlighted (and, where tree-sitter is involved, structurally navigable) as MF2. Outside the sigil the file is plain Elixir.

Classic Vim cannot cleanly do this with its regex syntax engine — use Neovim with nvim-mf2 if you rely on sigil highlighting.

TextMate, VS Code, and the "TextMate grammar" format

"TextMate grammar" is a regex-based format (.tmLanguage), originally from the TextMate editor, now consumed by VS Code, Sublime Text, Nova, and others. It is not tree-sitter, and none of those editors currently use tree-sitter as their primary highlighter for third-party languages:

• TextMate (the editor) — regex grammars only. Our vscode-mf2/syntaxes/mf2.tmLanguage.json works there directly.
• VS Code — TextMate is the supported route for extensions. VS Code has some internal tree-sitter usage for a handful of built-in languages but no public API for third-party tree-sitter grammars yet.
• Sublime Text 4 — primary highlighter is .sublime-syntax (a regex format derived from TextMate). Tree-sitter integration exists but is optional and requires additional plumbing per language.
• Nova — regex only.

In practice, the same TextMate grammar file we ship for VS Code can be rewrapped for TextMate, Sublime Text, and Nova with trivial packaging changes. Tree-sitter-native editors (Neovim, Helix, Zed, Emacs 29+, Lapce) consume tree-sitter-mf2/ directly.

Editors we don't target (yet)

• Sublime Text. Uses .sublime-syntax (YAML) grammars. Writable from the TextMate grammar with modest translation effort.

• JetBrains IDEs (IntelliJ, WebStorm, RustRover, etc.). Requires a full JetBrains plugin project in Kotlin/Java — significant effort. Out of scope until demand exists.

• Kakoune, Lapce, Nova. Niche; happy to accept PRs, not actively targeting.

If you want MF2 support in an editor not listed here and that editor supports tree-sitter, the tree-sitter-mf2/ grammar and queries should port over with very little work — most tree-sitter hosts use the same .scm query format.

Why a separate repo?

The Localize Elixir library is a runtime / build-time package on hex.pm. Editor extensions:

• have different release cadences and registries (Zed Extensions, VS Code Marketplace, nvim-treesitter parser registry, vim-plug-able git repos);
• depend on different tooling (Node, tree-sitter CLI, vsce);
• target consumers who are not Elixir users and shouldn't need to install the hex package.

Keeping editor assets here avoids polluting the Elixir package with non-Elixir files and lets each artefact have its own versioning and CI.

Licence

Apache-2.0. See the root LICENSE file.