Tazel

Tazel is the build system and package manager of Tala. The name joins Tala and Bazel. It moved from the compiler repository with its history on 2026-10-18.

Tazel is a Kotlin program for the JVM (25 or newer). It reads the project file, finds the sources and starts the compiler, the formatter or the linter as separate programs: Talac, talafmt and talalint. It compiles nothing itself and shares no code with them.

tazel check
tazel build
tazel run -- arguments for the program
tazel fmt -- --check
tazel lint -- --fix

Documentation

• The tazel command: every command, target selection, workspaces, the dependency graph.
• Tala project files: the project file, block by block. BUILD.kts is the whole DSL in one file; a test evaluates it.
• The lockfile: what LOCK.sqlite3 records, when it is written, and its text dump.
• Writing a plugin: the descriptor, the API, and how Tazel verifies and loads a plugin.
• How Tazel works: one command followed through the code.
• Contributing: checks, tests, conventions, adding a command, releases.

The site of Tazel is tazel.tala.run.

Layout

Package	Holds
com.progmasoft.tazel.cli	the command line: the typed parser, the commands, main
com.progmasoft.tazel.dsl	the project DSL, its model and the loader that evaluates a project file
com.progmasoft.tazel.dsl.plugin	the plugin host: preamble, resolution, the ViGet download, verification, activation, build steps
com.progmasoft.tazel.driver	source discovery, compiler arguments, tool lookup, workspaces
com.progmasoft.tazel.lock	LOCK.sqlite3 and LOCK.dump
com.progmasoft.api.tazel.dsl.plugin	the API a plugin is written against, in api/ (com.progmasoft.tazel:tazel-api)
com.progmasoft.tazel.gradle	the Gradle plugin com.progmasoft.tazel.plugin for building plugins, in gradle-plugin/

The command line is read by a parser written by hand; there is no command-line library. Terminal output goes through Mordant. The project file is compiled and run inside Tazel by the embedded Kotlin scripting host, so no Kotlin installation is needed beside the JRE.

Building and testing

.\gradlew.bat check          # format check and tests
.\gradlew.bat installDist    # build\install\tazel\bin\tazel(.bat)

The same steps, and a few more, are available as one Kotlin script built on Clikt. It needs JDK 25 and the kotlin launcher. The GitHub runners have it. Elsewhere, unpack kotlin-compiler-<version>.zip from the Kotlin releases and put its kotlinc/bin on PATH; the launcher under plugins/Kotlin/kotlinc/bin in IntelliJ IDEA works too:

kotlin helpers/develop.main.kts --help
kotlin helpers/develop.main.kts doctor          # JDK, Gradle wrapper, Git, and the Tala tools Tazel would start
kotlin helpers/develop.main.kts check           # what CI runs, with the Markdown links
kotlin helpers/develop.main.kts test --tests '*LockTest'
kotlin helpers/develop.main.kts run -- lock graph
kotlin helpers/develop.main.kts bundle          # distribution archives, smoke-tested, with .sha256 files
kotlin helpers/develop.main.kts coverage        # JaCoCo line, branch and method coverage
kotlin helpers/develop.main.kts version         # build.gradle.kts and CHANGELOG.md agree
kotlin helpers/develop.main.kts version --set 0.2.0
kotlin helpers/develop.main.kts version --release 0.2.0   # and the tag tazel-0.2.0 is new
kotlin helpers/develop.main.kts release-notes 0.2.0
kotlin helpers/develop.main.kts info            # checkout, version, JDK; nothing changes
kotlin helpers/develop.main.kts verify-docs     # every relative Markdown link and anchor
kotlin helpers/develop.main.kts clean --dry-run # build/, .gradle/, .kotlin/
kotlin helpers/develop.main.kts self-test       # the script's own logic

Every program the script starts is one step; a table of the steps and their times closes a command that ran more than one, and on GitHub Actions each step is a collapsible group that also goes to the job summary. bundle builds the .zip and .tar distributions, runs the installed launcher with version, and writes the SHA-256 of each archive beside it; the archives keep no file times, so a commit packs into the same bytes.

version --set writes the version into build.gradle.kts and turns the notes under ## Unreleased in CHANGELOG.md into the section of that version, dated today. The command line of Tazel itself stays hand-written; Clikt is used only by this developer script.

Every resolved dependency is locked in gradle.lockfile, which OSV-Scanner also reads. After changing a dependency, run .\gradlew.bat dependencies --write-locks and commit the lock file with the change.

Tazel finds a tool through TAZEL_TALAC, TAZEL_TALAFMT or TAZEL_TALALINT, then in the installation it runs from, then on PATH. To try a development build against a compiler built by Bazel:

$env:TAZEL_TALAC = "..\bazel-bin\Talac\Cli\talac.exe"
.\build\install\tazel\bin\tazel.bat build

The tests run whole commands against projects on disk with stand-in tools that record their command line, so they need no compiler.