Emacs major mode for editing Templ files.
templ-ts-mode is available in MELPA. Install it however you usually install your emacs packages from MELPA!
The mode does require two tree-sitter grammars: the Javascript grammar, which should have shipped with your Emacs installation; and the Templ grammar, which probably hasn't.
By default, if the Templ grammar is missing, templ-ts-mode will ask if
you want to download and build it using Emacs' built-in
treesit-install-language-grammar machinery. If you want to do this,
you need to have git and a C compiler installed. There are Customize
options to set the source repository for the grammar, and to either
always or never install the grammar if it's missing.
If you're a Nix/NixOS user, this repository is a flake that packages both the major mode and the tree-sitter grammar as a convenience. I recommend using the community emacs overlay to manage your emacs configs, and you can peek at my emacs nix configuration for an example of how to add the parser and major mode to your installation.
The package automatically sets templ-ts-mode for .templ
files. Currently, font-locking and indentation work, but Imenu and
other creature comforts aren't done yet.
templ-ts-mode does not define its own customization variables for indentation. Instead, it piggybacks on the settings for the languages that make up a Templ file:
go-ts-mode-indent-offset.script functions is indented according to
js-indent-level.Indentation is slightly buggy on the first line of script
components: the point must be at or before the first character on the
line for indentation to do anything. This is due to a bug in Emacs
29.1 relating to multi-language indentation handling and is already
fixed in git, so the bug will go away with the next Emacs update.
CSS font-locking is currently freelanced, rather than delegating to css-mode. This is because Templ's CSS components are tricksy and can include embedded chunks of Go, which makes it difficult to delegate parsing and font-locking to css-ts-mode without causing chaos.
There may be corners of the Templ language that I missed in my testing, so indentation and font-locking may be imperfect. Patches are welcome.