Language toolchain modules

These modules detect that the current directory is a project of a particular language, then show the version of the relevant toolchain. They follow a near-identical shape; this page describes the shape once and lists the modules that fit it.

Common shape

A typical toolchain module:

1. Loads its <Name>Config struct (which has at minimum format, symbol, style, disabled, detect_files, detect_extensions, detect_folders, version_format).
2. Detects a project via Context::try_begin_scan() matching detect_files, detect_extensions, or detect_folders.
3. Resolves the toolchain version, usually by:
   • calling context.exec_cmd("rustc", &["--version"]) (mockable in tests via ModuleRenderer::cmd),
   • or reading a manifest file (Cargo.toml, pyproject.toml, package.json, go.mod, …) directly with Context::read_file_from_pwd,
   • or honoring an environment variable (PYENV_VERSION, RBENV_VERSION, JAVA_HOME, …).
4. Formats the raw version string via VersionFormatter::format_module_version, which trims leading v, allows the user to drop minor/patch parts (v${major}.${minor}), and so on.
5. Renders through StringFormatter with the standard $symbol, $style, $version variables.

Modules in this group

Module	Default symbol	Detection	Notes
bun	🥟	bun.lock, bun.lockb, bunfig.toml	Reads version from bun --version
c	C	*.c, *.h	Compiler info via cc --version (or alternatives in commands config)
cmake	△	CMakeLists.txt, CMakeCache.txt
cobol	⚙️	*.cbl, *.cob, *.cpy, *.cobol
cpp	C++	*.cpp, *.hpp, *.cxx, *.cc	Compiler detection mirrors c
crystal	🔮	shard.yml, *.cr
daml	Λ	daml.yaml	Daml SDK version
dart	🎯	*.dart, pubspec.yaml, .dart_tool/
deno	🦕	deno.json, deno.jsonc, mod.ts, mod.js, deps.ts, deps.js
dotnet	.NET	*.csproj, global.json, *.sln, Directory.Build.props, …	Honors global.json SDK pinning
elixir	💧	mix.exs	Shows OTP and Elixir versions
elm	🌳	elm.json, elm-package.json, elm-stuff/, *.elm
erlang	🖧	rebar.config, erlang.mk
fennel	🧅	*.fnl
fortran	❄️	*.f, *.for, *.f90, *.f95, *.f03, *.f08, fpm.toml
gleam	⭐	gleam.toml, *.gleam
golang (variable: golang, config key golang)	🐹	go.mod, go.sum, go.work, glide.yaml, Gopkg.yml, Gopkg.lock, .go-version, *.go, Godeps/	Honors GOROOT and go.mod go directive
gradle	🅶	gradlew, *.gradle, *.gradle.kts	Reads gradle/wrapper/gradle-wrapper.properties
haskell	λ	*.hs, cabal.project, stack.yaml, package.yaml
haxe	⌘	*.hx, *.hxml
helm	⎈	Chart.yaml, helmfile.yaml, helmfile.lock
java	☕	pom.xml, build.gradle.kts, build.sbt, *.java, *.class, *.jar, .java-version, deps.edn, project.clj, build.boot, .sdkmanrc
julia	ஃ	Project.toml, Manifest.toml, *.jl
kotlin	🅺	*.kt, *.kts
lua	🌙	.lua-version, lua/, *.lua
maven	🅼	pom.xml	Reads Maven Wrapper version
mojo	🔥	mojoproject.toml, *.mojo, *.🔥
nim	👑	*.nim, *.nims, *.nimble, nim.cfg
nodejs		package.json, .node-version, .nvmrc, node_modules/, *.js, *.mjs, *.cjs, *.ts, *.mts, *.cts	Honors engines.node field
ocaml	🐫	*.opam, _opam/, esy.lock/, dune, dune-project, jbuild, jbuild-ignore, .merlin, *.ml, *.mli, *.re, *.rei
odin	Ø	*.odin
opa	🪖	*.rego
perl	🐪	Makefile.PL, Build.PL, cpanfile, cpanfile.snapshot, META.json, META.yml, .perl-version, *.pl, *.pm, *.pod
php	🐘	composer.json, .php-version, *.php
purescript	<=>	spago.dhall, spago.yaml, spago.lock, *.purs
python	🐍	requirements.txt, pyproject.toml, pyrightconfig.json, setup.py, tox.ini, Pipfile, __init__.py, *.py, *.ipynb, .python-version, .venv/, venv/	Honors pyenv, pyvenv.cfg, VIRTUAL_ENV, CONDA_DEFAULT_ENV
quarto	⨁	_quarto.yml, *.qmd
raku	🦋	META6.json, *.p6, *.pm6, *.raku, *.rakumod, *.pod6
red	🔺	*.red, *.reds
rlang (variable: rlang, config key rlang)	📐	.Rprofile, .Rproj.user/, *.R, *.Rd, *.Rmd, *.Rproj, *.Rsx, .Rdata, .Rhistory
ruby	💎	Gemfile, .ruby-version, *.rb	Honors RUBY_VERSION
rust	🦀	Cargo.toml, *.rs	The biggest module in the group at ~950 lines; resolves toolchain via rustup overrides, rust-toolchain.toml, env vars, then rustc -vV
scala	🆂	.scalaenv, .sbtenv, build.sbt, .metals/, .bloop/, *.scala, *.sbt
solidity	S	*.sol
swift	🐦	Package.swift, *.swift
terraform	💠	.terraform/, *.tf, *.tfplan, *.tfstate	Shows current workspace + version
typst	t	template.typ, *.typ
vagrant	⍱	Vagrantfile
vlang (config key vlang, variable vlang)	V	*.v, v.mod, vpkg.json, .vpkg-lock.json
xmake	🧰	xmake.lua
zig	↯	*.zig

A handful of toolchain-adjacent modules show environment-name-only (no version):

Module	Default symbol	Trigger	Notes
conda	🅒	CONDA_DEFAULT_ENV is set	Activated env name only
pixi	🧚	Project files; honors PIXI_ENVIRONMENT_NAME	Optionally shows version
direnv	direnv loaded	direnv state file detected
mise	mise	mise output
nix_shell	❄️	IN_NIX_SHELL is set
guix_shell	[guix]	GUIX_ENVIRONMENT is set
spack	🅢	SPACK_ENV is set
meson	⬢	MESON_DEVENV and MESON_PROJECT_NAME set
quarto	⨁	(already listed above)
buf	🐃	buf.yaml, buf.gen.yaml, buf.work.yaml	Buf CLI version

Key abstractions reused across the group

Helper	File	Purpose
VersionFormatter::format_module_version	src/formatter/version.rs	Trims v prefix, applies version_format template
Context::try_begin_scan	src/context.rs	One-pass scan of the current directory's files, folders, and extensions
Context::exec_cmd	src/context.rs	Runs a command with a configurable timeout, mockable in tests
Context::read_file_from_pwd	src/context.rs	Reads a file but only after a scan confirms it is present (saves a stat)
Context::detect_env_vars	src/context.rs	Trigger on env var presence, with !VAR for negation

Entry points for modification

To change how a toolchain module detects projects, edit the detect_files / detect_extensions / detect_folders defaults in src/configs/<name>.rs. To change how it resolves the version, edit the module(context) function in src/modules/<name>.rs — almost always the change is in the part that calls context.exec_cmd or read_file_from_pwd. Tests live at the bottom of the same file and use ModuleRenderer.

For new languages, see Adding a new module.