This version is still in development and is not considered stable yet. For the latest stable version, please use fluent-tooling 0.0.1!

Emacs integration

fluent-ts-mode is a native Tree-sitter major mode for Fluent FTL resources. It requires Emacs 29.1 or newer with built-in Tree-sitter support.

The mode registers .ftl files and provides syntax highlighting, four-space indentation, comments, Imenu, defun navigation, and syntax navigation. It can check unsaved buffer contents with built-in Flymake or optional Flycheck support through ftl-lint.

The Emacs package does not bundle a compiled grammar. Install the package and then install or expose the grammar explicitly. Opening an .ftl file never downloads or installs software.

Install the package

Vanilla Emacs with `package-vc`

Emacs 29.1 and newer can install the package directly from this repository:

(package-vc-install
 '(fluent-ts-mode
   :url "https://github.com/outskirtslabs/fluent-tooling"
   :lisp-dir "editors/emacs"
   :main-file "fluent-ts-mode.el"))

(require 'fluent-ts-mode)

straight.el

(straight-use-package
 '(fluent-ts-mode
   :type git
   :host github
   :repo "outskirtslabs/fluent-tooling"
   :files ("editors/emacs/*.el")))

Doom Emacs

Add the package recipe to packages.el:

(package! fluent-ts-mode
  :recipe (:host github
           :repo "outskirtslabs/fluent-tooling"
           :files ("editors/emacs/*.el")))

Run doom sync, then load and configure the mode from config.el or a language module:

(require 'fluent-ts-mode)
(setq fluent-ts-mode-checker 'auto)

Local checkout

Load the package directly while developing it:

(add-to-list 'load-path
             "/absolute/path/to/fluent-tooling/editors/emacs")
(require 'fluent-ts-mode)

Install the grammar

Choose one of the following methods. Install the grammar before opening an FTL file with fluent-ts-mode.

Build from the public source recipe

Run M-x fluent-ts-mode-install-grammar. The command asks Emacs’s built-in Tree-sitter installer to clone this repository, compile src/parser.c and src/scanner.c, and install the resulting shared library. This command is the only part of fluent-ts-mode that may access the network.

With a prefix argument, the command prompts for an installation directory:

C-u M-x fluent-ts-mode-install-grammar

Build from a local checkout

Replace the public recipe after loading the mode, then run the installation command:

(require 'fluent-ts-mode)
(setf (alist-get 'fluent treesit-language-source-alist)
      '("/absolute/path/to/fluent-tooling"))

Use the Nix grammar package

Build the grammar and add its library directory to Emacs’s search path:

nix build .#tree-sitter-fluent

(require 'treesit)
(add-to-list 'treesit-extra-load-path
             "/absolute/path/to/fluent-tooling/result/lib")
(require 'fluent-ts-mode)

Keep the result link available, or use the grammar’s immutable Nix store path. Evaluate (treesit-language-available-p 'fluent) to confirm that Emacs can load it.

Configure diagnostics

fluent-ts-mode-checker controls diagnostics:

Value Behavior

Value	Behavior
`auto`	Use Flycheck when it is already loaded; otherwise use Flymake
`flymake`	Use built-in Flymake
`flycheck`	Require and use Flycheck
`nil`	Disable diagnostics

auto

Use Flycheck when it is already loaded; otherwise use Flymake

flymake

Use built-in Flymake

flycheck

Require and use Flycheck

nil

Disable diagnostics

The default is auto. Load Flycheck before opening an FTL buffer when you want automatic selection to choose it:

(require 'flycheck)
(setq fluent-ts-mode-checker 'auto)

Both adapters send unsaved buffer contents to ftl-lint --format json -. Install ftl-lint on Emacs’s exec-path, or set its absolute path:

(setq fluent-ts-mode-linter-executable
      "/absolute/path/to/ftl-lint")

Select a frontend explicitly when needed:

(setq fluent-ts-mode-checker 'flymake)
;; or
(setq fluent-ts-mode-checker 'flycheck)

The adapters consume the stable ftl-lint JSON diagnostics protocol.

Customize indentation

Fluent continuation lines use four spaces by default:

(setq fluent-ts-mode-indent-offset 4)

Troubleshooting

If mode activation reports that the grammar is unavailable, install it or add its library directory to treesit-extra-load-path before opening the file.
If diagnostics report that ftl-lint cannot be started, check (executable-find "ftl-lint") or set fluent-ts-mode-linter-executable explicitly.
If auto selects Flymake, load Flycheck before activating the FTL buffer or set fluent-ts-mode-checker to flycheck.