Language & Syntax Highlighting Support Review

How Syntax Highlighting Works in Fresh

Fresh keeps every known language in a unified grammar catalog (GrammarRegistry::catalog). Each entry records which engines can serve it:

• Syntect (TextMate/Sublime grammars) — the primary highlighting engine, covering ~115 built-in and embedded grammars.
• Tree-sitter — used for structural features (auto-indent, bracket matching, semantic highlighting) and as a highlighting fallback for the ~18 languages it supports. Notably, TypeScript is tree-sitter-only — syntect ships no grammar for it.

A single catalog entry may be served by syntect, tree-sitter, or both.

Lookup API

All resolution happens through three methods on GrammarRegistry:

• find_by_path(&Path) — filename → glob → extension, honouring user [languages] config (filenames, globs, extensions all merged into the catalog via apply_language_config).
• find_by_name(&str) — display name, language id, short alias, all case-insensitive, single HashMap lookup.
• find_by_extension(&str) — just the extension index.

Each returns Option<&GrammarEntry>. HighlightEngine::from_entry and DetectedLanguage::from_entry consume those entries. The "prefer syntect, else tree-sitter, else None" fallback lives in exactly one place: HighlightEngine::from_entry.

Adding a language

• New syntect grammar — drop a .sublime-syntax into crates/fresh-editor/src/grammars/ and register it in GrammarRegistry::add_embedded_grammars. The catalog picks it up on the next rebuild.
• New tree-sitter language — add a variant to fresh_languages::Language (extensions, display_name, highlight_config). The catalog auto-creates a tree-sitter-only entry if no syntect grammar matches.
• User config mapping — edit ~/.config/fresh/config.toml [languages] section. Extensions, exact filenames, and globs all merge through apply_language_config into the catalog.

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Summary

This document catalogs all language support requests from GitHub issues, combined with common DevOps/infrastructure languages and file types that developers expect modern editors to handle. It compares against Fresh's current support levels.

Support Level Key

Level	Meaning
Syntect (built-in)	Highlighting via syntect's built-in TextMate grammar defaults (~100 languages)
Embedded grammar	Custom .sublime-syntax file bundled with Fresh (better/specialized highlighting)
Tree-sitter	Structural features: auto-indent, bracket matching, semantic highlighting; fallback syntax highlighting
LSP config	Built-in LSP server configuration in config.example.json
None	No current support

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Languages Requested in GitHub Issues

Language	Issue(s)	Status	Current Support	What's Missing
Dart	#1252	Open	Syntect (basic)	LSP config (dart analyze --lsp)
KDL	#1266	Open	None	TextMate grammar (.sublime-syntax)
Hyprlang	#1266	Open	None	TextMate grammar (.sublime-syntax)
Nushell	#1031	Open	None	TextMate grammar, LSP config (nu --lsp)
Solidity	#857	Closed	None	TextMate grammar, LSP config (solc --lsp)
Deno (TS variant)	#1191	Open	TypeScript supported	Deno LSP auto-detection (deno.json presence)
LaTeX	#807	Closed/Added	Syntect + LSP config	Done (highlighting via syntect)
Zig	#737	Closed/Added	Embedded grammar + LSP	Done
Bash/Zsh configs	#383	Closed/Added	Tree-sitter + Syntect	Done
Config file fallback	#1219	Added (v0.2.18)	fallback config field	Set "fallback": {"grammar": "bash", "comment_prefix": "#"} in config. See Configuration docs.

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Common DevOps / Infrastructure Languages & Files

Language / File Type	File Extensions / Names	Current Support	Recommendation
Dockerfile	Dockerfile, Dockerfile.*, *.dockerfile	Syntect + LSP config	Adequate (highlighting works)
Docker Compose	docker-compose.yml, compose.yml	YAML (Syntect)	Adequate (YAML grammar)
Makefile	Makefile, *.mk, GNUmakefile	Syntect + LSP config	Adequate (highlighting works)
CMake	CMakeLists.txt, *.cmake	Syntect	Add LSP config (cmake-language-server)
Terraform / HCL	*.tf, *.tfvars, *.hcl	None	Add TextMate grammar + LSP config (terraform-ls)
Helm templates	*.tpl (in chart dirs)	None	Add Go template grammar
Nix	*.nix, flake.nix	Syntect	Add LSP config (nil/nixd)
Shell (POSIX)	*.sh, *.bash, *.zsh	Syntect + Tree-sitter + LSP	Done
PowerShell	*.ps1, *.psm1, *.psd1	Syntect	Add LSP config (powershell-editor-services)
YAML	*.yml, *.yaml	Syntect + LSP config	Adequate (highlighting works)
TOML	*.toml	Embedded grammar + LSP	Adequate
JSON / JSONC	*.json, *.jsonc	Syntect + Tree-sitter + LSP	Done
XML	*.xml, *.xsl, *.xsd, *.svg	Syntect	Adequate; optionally add LSP config
INI / CONF	*.ini, *.conf, *.cfg, *.env	Syntect (INI)	Add .env grammar
Protobuf	*.proto	None	Add TextMate grammar + LSP config (buf-language-server)
GraphQL	*.graphql, *.gql	None	Add TextMate grammar + LSP config (graphql-lsp)
SQL	*.sql	Syntect	Add LSP config (sqls)

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Common Programming Languages (Not Yet Fully Supported)

Language	File Extensions	Current Support	Recommendation
Kotlin	*.kt, *.kts	Syntect	Add LSP config (kotlin-language-server)
Swift	*.swift	Syntect	Add LSP config (sourcekit-lsp)
Scala	*.scala, *.sc	Syntect	Add LSP config (metals)
Elixir	*.ex, *.exs	Syntect	Add LSP config (elixir-ls)
Erlang	*.erl, *.hrl	Syntect	Add LSP config (erlang_ls)
Haskell	*.hs, *.lhs	Syntect	Add LSP config (haskell-language-server)
OCaml	*.ml, *.mli	Syntect	Add LSP config (ocamllsp)
Clojure	*.clj, *.cljs, *.cljc	Syntect	Add LSP config (clojure-lsp)
R	*.r, *.R, *.Rmd	Syntect	Add LSP config (languageserver)
Julia	*.jl	None	Add TextMate grammar + LSP config (LanguageServer.jl)
Perl	*.pl, *.pm	Syntect	Add LSP config (Perl::LanguageServer)
Dart	*.dart	Syntect (basic)	Add LSP config (dart analyze --lsp)
V	*.v	None	Add TextMate grammar
Nim	*.nim, *.nims	None	Add TextMate grammar, LSP config (nimlangserver)
Gleam	*.gleam	None	Add TextMate grammar, LSP config (gleam lsp)

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Web Frontend Languages

Language	File Extensions	Current Support	Recommendation
Vue	*.vue	None	Add TextMate grammar + LSP config (vue-language-server)
Svelte	*.svelte	None	Add TextMate grammar + LSP config (svelte-language-server)
Astro	*.astro	None	Add TextMate grammar + LSP config (@astrojs/language-server)
SCSS	*.scss	Syntect (Sass)	Add LSP config (vscode-css-languageserver)
LESS	*.less	Syntect	Add LSP config (vscode-css-languageserver)
Tailwind CSS	(within HTML/JSX)	None	Add LSP config (tailwindcss-language-server)

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Package Manager & Build Tool Config Files

File Type	File Names / Extensions	Current Support	Recommendation
npm	package.json, package-lock.json, .npmrc	JSON grammar	Adequate
pip / PyPI	requirements.txt, pyproject.toml, setup.cfg, Pipfile	TOML/INI grammars	Adequate
uv	uv.toml, uv.lock	TOML grammar	Adequate
Cargo (Rust)	Cargo.toml, Cargo.lock	TOML grammar	Adequate
Go modules	go.mod, go.sum	None (specific)	Add go.mod grammar
Gradle	build.gradle, build.gradle.kts, settings.gradle	Syntect (Groovy) / None (kts)	Add Kotlin script support
Maven	pom.xml	XML grammar	Adequate
Bazel / Buck	BUILD, BUILD.bazel, WORKSPACE, *.bzl	None	Add Starlark grammar
Meson	meson.build, meson_options.txt	None	Add grammar
Justfile	justfile, Justfile, .justfile	None	Add grammar (similar to Makefile)
Taskfile	Taskfile.yml, Taskfile.yaml	YAML grammar	Adequate
Tiltfile	Tiltfile	None	Add Starlark grammar
Earthfile	Earthfile	None	Add Dockerfile-like grammar
Podfile	Podfile	Syntect (Ruby)	Adequate
Gemfile	Gemfile, *.gemspec	Syntect (Ruby)	Adequate
Brewfile	Brewfile	None	Map to Ruby grammar

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CI/CD & Orchestration Config Files

File Type	File Names / Extensions	Current Support	Recommendation
GitHub Actions	.github/workflows/*.yml	YAML grammar	Adequate
GitLab CI	.gitlab-ci.yml	YAML grammar	Adequate
Jenkinsfile	Jenkinsfile	None	Map to Groovy grammar
CircleCI	.circleci/config.yml	YAML grammar	Adequate
Kubernetes manifests	*.yaml (k8s)	YAML grammar	Adequate
Ansible	*.yml (playbooks)	YAML grammar	Adequate
Vagrant	Vagrantfile	None	Map to Ruby grammar

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Data & Markup Formats

Format	File Extensions	Current Support	Recommendation
Markdown	*.md, *.mdx	Syntect + LSP config	Adequate (highlighting works)
reStructuredText	*.rst	Syntect	Adequate
AsciiDoc	*.adoc, *.asciidoc	None	Add grammar
CSV / TSV	*.csv, *.tsv	None	Add basic grammar (rainbow CSV)
Diff / Patch	*.diff, *.patch	Syntect	Adequate
Dotenv	.env, .env.*	None	Add grammar
EditorConfig	.editorconfig	None	Map to INI grammar
Ignore files	.gitignore, .dockerignore	Embedded grammar	Done

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Priority Recommendations

High Priority (Frequently Requested + Common DevOps)

#	Language/File	What to Add	Reason
1	Terraform / HCL	TextMate grammar + LSP config	Very common in DevOps, zero support
2	Dart	LSP config	Requested in #1252, already has syntect highlighting
3	Nix	LSP config (nil/nixd)	Already has syntect highlighting, project uses Nix
4	Vue / Svelte	TextMate grammar + LSP config	Very popular web frameworks, no support at all
5	Protobuf	TextMate grammar + LSP config	Common in microservices, no support
6	GraphQL	TextMate grammar + LSP config	Common in web APIs, no support
7	Kotlin	LSP config	Already has syntect highlighting, major language
8	SQL	LSP config (sqls)	Already has syntect highlighting, very common
9	CMake	LSP config	Already has syntect highlighting, common build system
10	PowerShell	LSP config	Already has syntect highlighting, common on Windows

Medium Priority (Requested in Issues)

#	Language/File	Reason
11	KDL	Requested in #1266
12	Hyprlang	Requested in #1266, niche but passionate users
13	Nushell	Requested in #1031
14	Solidity	Requested in #857
15	Deno LSP detection	Requested in #1191
16	Config file fallback	Requested in #1219, broad impact

Lower Priority (Nice to Have)

#	Language/File	Reason
17	Starlark (Bazel/Tiltfile/Buck)	Niche but useful
18	Justfile	Growing popularity
19	Gleam	New but growing
20	Nim	Small community
21	Astro	Web framework
22	Dotenv	Simple but useful
23	go.mod	Small grammar
24	Meson	Build system

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Validated Syntax Highlighting Results (tmux capture-pane -e)

Tested by opening each file in Fresh via tmux, capturing the terminal output with ANSI escape codes (tmux capture-pane -e -p), and checking for syntax-colored tokens (colors beyond default text white/gray).

WORKING - Full syntax highlighting (55 files)

File	Detected Syntax	Engine	Colors
hello.rs	Rust	tree-sitter	4 (keywords, strings, functions, types)
hello.py	Python	tree-sitter	5
hello.js	JavaScript	tree-sitter	4
hello.ts	typescript	tree-sitter	6
hello.tsx	typescript	tree-sitter	6
hello.jsx	JavaScript	syntect	6
hello.mjs	JavaScript	syntect	6
hello.go	Go	syntect	5
hello.c	C	syntect	5
hello.h	C	syntect	6
hello.cpp	C++	syntect	5
hello.cc	C++	syntect	6
hello.hpp	C++	syntect	6
hello.cs	C#	syntect	4
hello.java	Java	syntect	4
hello.php	PHP	syntect	5
hello.rb	Ruby	syntect	4
hello.lua	Lua	syntect	5
hello.sh	Bourne Again Shell	syntect	4
hello.bash	Bourne Again Shell	syntect	4
hello.zsh	Bourne Again Shell	syntect	3
dot_bashrc	Bourne Again Shell	syntect	4
dot_profile	Bourne Again Shell	syntect	4
hello.json	JSON	tree-sitter	3
hello.html	HTML	syntect	3
hello.css	CSS	syntect	3
hello.py	Python	syntect	5
hello.pyi	Python	syntect	5
hello.toml	TOML	syntect (embedded)	4
hello.zig	Zig	syntect (embedded)	6
hello.odin	Odin	syntect (embedded)	6
hello.typ	Typst	syntect (embedded)	5
hello.gitconfig	Git Config	syntect (embedded)	3
hello.yaml	YAML	syntect	3
docker-compose.yml	YAML	syntect	3
hello.xml	XML	syntect	4
hello.md	Markdown	syntect	5
hello.sql	SQL	syntect	6
hello.tex	LaTeX	syntect	5
hello.r	R	syntect	5
hello.scala	Scala	syntect	4
hello.hs	Haskell	syntect	6
hello.clj	Clojure	syntect	6
hello.erl	Erlang	syntect	6
hello.ml	OCaml	syntect	6
hello.pl	Perl	syntect	6
hello.lisp	Lisp	syntect	6
hello.d	D	syntect	6
hello.bat	Batch File	syntect	4
Makefile	Makefile	syntect	5
GNUmakefile	Makefile	syntect	5
hello.mk	Makefile	syntect	5
Gemfile	Ruby	syntect	4
Rakefile	Ruby	syntect	6
Vagrantfile	Ruby	syntect	6

PARTIAL - Detected but minimal/no highlighting colors (4 files)

File	Detected Syntax	Issue
hello.gitignore	Gitignore	Only 2 highlight colors (comment green + path gray)
hello.diff	Diff	Syntax detected but 0 highlight colors (scope-to-category mapping gap)
hello.mts	typescript	Tree-sitter detected but no highlighting rendered
hello.vue	text	Only tag bracket color (220/gold)

NOT WORKING - No syntax highlighting (35 files)

File	Detected As	Reason	Fix Needed
Dockerfile	dockerfile	Tree-sitter detects language but no TextMate grammar	Add Dockerfile.sublime-syntax
Dockerfile.dev	text	Not detected at all (variant filename)	Add filename pattern
Containerfile	dockerfile	Same as Dockerfile	Add Dockerfile.sublime-syntax
CMakeLists.txt	Plain Text	No CMake grammar in syntect defaults	Add CMake.sublime-syntax
hello.kt	text	No Kotlin grammar in syntect	Add Kotlin.sublime-syntax
hello.swift	text	No Swift grammar in syntect	Add Swift.sublime-syntax
hello.dart	text	No Dart grammar in syntect	Add Dart.sublime-syntax
hello.ex	text	No Elixir grammar in syntect	Add Elixir.sublime-syntax
hello.fs	text	No F# grammar in syntect	Add FSharp.sublime-syntax
hello.nix	text	No Nix grammar in syntect	Add Nix.sublime-syntax
hello.ps1	text	No PowerShell grammar in syntect	Add PowerShell.sublime-syntax
hello.scss	text	No SCSS grammar in syntect	Add SCSS.sublime-syntax
hello.less	text	No LESS grammar in syntect	Add LESS.sublime-syntax
hello.ini	text	No INI grammar in syntect	Add INI.sublime-syntax
hello.cjs	text	.cjs not mapped to JavaScript	Add extension mapping
hello.jl	text	No Julia grammar in syntect	Add Julia.sublime-syntax
hello.nim	text	No Nim grammar in syntect	Add Nim.sublime-syntax
hello.gleam	text	No Gleam grammar in syntect	Add Gleam.sublime-syntax
hello.v	text	No V grammar in syntect	Add V.sublime-syntax
hello.sol	text	No Solidity grammar in syntect	Add Solidity.sublime-syntax
hello.kdl	text	No KDL grammar in syntect	Add KDL.sublime-syntax
hello.nu	text	No Nushell grammar in syntect	Add Nushell.sublime-syntax
hello.tf	text	No Terraform/HCL grammar	Add HCL.sublime-syntax
hello.proto	text	No Protobuf grammar in syntect	Add Protobuf.sublime-syntax
hello.graphql	text	No GraphQL grammar in syntect	Add GraphQL.sublime-syntax
hello.astro	text	No Astro grammar in syntect	Add Astro.sublime-syntax
hello.svelte	text	No Svelte grammar (partial tag color)	Add Svelte.sublime-syntax
hello.env	text	No dotenv grammar	Add env.sublime-syntax
hello.editorconfig	text	No editorconfig grammar	Map to INI grammar
BUILD.bazel	text	No Starlark grammar	Add Starlark.sublime-syntax
Jenkinsfile	text	Not mapped to Groovy	Add filename mapping
Tiltfile	text	No Starlark grammar	Add Starlark.sublime-syntax
Earthfile	text	No Earthfile grammar	Add Earthfile.sublime-syntax
justfile	text	No Justfile grammar	Add Justfile.sublime-syntax
go.mod	text	No go.mod grammar	Add go.mod.sublime-syntax

Bugs Found

1. hello.diff: Diff grammar IS in syntect and IS detected, but produces zero highlight colors. The scope-to-category mapping in textmate_engine.rs doesn't handle Diff scopes (markup.inserted, markup.deleted, meta.diff.header, punctuation.definition.from-file).

2. hello.mts: Tree-sitter detects TypeScript but produces no colors. The .mts extension may not be triggering the highlight engine properly despite status bar showing "typescript".

3. Dockerfile / Containerfile: Tree-sitter detects the language (status bar shows "dockerfile") but there's no TextMate grammar and tree-sitter fallback isn't producing colors.

4. Jenkinsfile: Syntect has Groovy grammar (with .groovy, .gvy, .gradle extensions) but Jenkinsfile isn't mapped to it.

5. hello.cjs: JavaScript grammar exists but .cjs extension isn't in its extension list (["js", "htc"]). Same issue for .mjs detection (though it works - may go through tree-sitter JS).

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Current Support Summary

• Syntect defaults (57 syntaxes): Primary highlighting engine. The actual built-in set is MUCH smaller than previously claimed (~57 syntaxes, NOT 100+). Notable absences: Kotlin, Swift, Dart, Elixir, Nix, PowerShell, SCSS, LESS, CMake, Dockerfile, F#, Julia, Nim, INI.
• Embedded grammars (9): TOML, Odin, Zig, Typst, Git Rebase, Git Commit, Gitignore, Git Config, Git Attributes
• Tree-sitter (18): Rust, Python, JavaScript, TypeScript, HTML, CSS, C, C++, Go, JSON, Java, C#, PHP, Ruby, Bash, Lua, Pascal, Odin. Used for auto-indent/brackets, and as highlighting fallback (works for TS/TSX, but NOT for Dockerfile).
• LSP configs (23): Bash, C, C++, C#, CSS, Go, HTML, Java, JavaScript, JSON, LaTeX, Lua, Markdown, PHP, Python, Ruby, Rust, Templ, TOML, TypeScript, Typst, YAML, Zig

What "adding a language" means in practice

Need	Action	Effort
Syntax highlighting for a language not in syntect defaults	Add a .sublime-syntax file to crates/fresh-editor/src/grammars/	Medium
LSP support for a language already highlighted	Add server config to config.example.json	Low
Better indentation/brackets for an existing language	Add tree-sitter parser + indent queries	High
Extension mapping for an existing grammar	Add to file_extensions list or filename_scopes	Low

Priority fixes (bugs in existing support)

1. Fix Diff scope-to-category mapping (markup.inserted/deleted not handled)
2. Fix .mts tree-sitter highlighting (detected but not rendered)
3. Add Dockerfile TextMate grammar (tree-sitter detects but can't highlight)
4. Map Jenkinsfile -> Groovy grammar
5. Map .cjs -> JavaScript grammar