moon v1.35 - Action graph improvements, task priorities, and more!

With this release, we're taking yet another step to supporting plugins.

Improved action graph

For this release we wanted to introduce a new WASM based Rust toolchain, but we encountered a few blockers while integrating with the action graph, so instead of working on the toolchain, we decided to rewrite the action graph to properly support plugins.

The biggest blocker was around locating the toolchain's dependency root, and in Rust's case, the Cargo workspace (where Cargo.lock is located). We technically have some of this logic in the current Rust platform, but it always assumed that the Cargo workspace was in the root of the moon workspace (the same applies to Bun and Node). This heavily restricted all moon users. With the new plugin system, the dependency root can be located anywhere in the moon workspace, and we'll attempt to locate it!

While rewriting the action graph, we made a ton of improvements (some won't be noticeable until plugins are more prevalent). To start the graph is now async compatible, and in the future, we'll update it to also support concurrency, so that the graph can be built in parallel across threads. Additionally, a main focus was reducing the amount of edges (relationships) being created between nodes (actions). And lastly, the following changes were made for the actions themselves.

• Added a new InstallDependencies action for WASM plugins.
  • The dependencies root is now dynamically located by traversing the file system, unlike the previous implementation that assumed everything was in the workspace root.
• Added a new SetupEnvironment action for WASM plugins.
  • This runs after SetupToolchain but before InstallDependencies.
  • Can be used to setup the workspace or project environment. For example, initializing Python venv, or making manifest/lockfile changes.
• Updated RunTask to setup toolchains and install dependencies for each toolchain that has been configured, instead of just the 1st one (work in progress).
• Updated SyncProject to no longer depend on SetupToolchain, and not be grouped by language/toolchain, and instead encompass all of them applicable to the project.

Task priorities

Based on a request from the community that we really liked, we're introducing a new concept called task priorities. Each task can configure a priority level using the new task option priority, and the priority level determines the position of the task within the action pipeline queue. A task with a higher priority will run sooner rather than later, while still respecting the topological order.

app/moon.yml

tasks:
  build:
    # ...
    options:
      priority: 'high'

There are a few things to be aware of with this implementation:

• All non-task related actions (like setup toolchain) will still always run first.
• Higher priority tasks that depend on lower priority tasks will effectively mark them as high priority, as we attempt to complete them sooner.
• The order within each priority level is sorted topological, but is still non-deterministic if tasks run in parallel.

Enabled experiments

In our last release, we introduced 2 new experiments, fasterGlobWalk and gitV2. In the past few weeks, we've had many users (including ourself) enable these experiments without issue. As such, we've decided to enable them by default in this release.

If you encounter an issue with either of these experiments, you can disable them in .moon/workspace.yml. And of course, please report it so we can fix it!

.moon/workspace.yml

experiments:
  fasterGlobWalk: false
  gitV2: false

Light terminal theme

By default, moon assumes a dark themed terminal is being used, and will output our branded colors accordingly. However, if you use a light theme, these colors are hard to read, and there's no way to change them.

To mitigate this, we're introducing a light based terminal theme, which can be enabled with the --theme global option, or the MOON_THEME environment variable.

$ moon run app:build --theme light
# Or
$ MOON_THEME=light moon run app:build

Other changes

View the official release for a full list of changes.

• Added a new task option, cacheKey, which can be used to seed the hash, and invalidate local and remote caches.
• Added a --log=verbose level, which includes span information on top of the trace level.
• Added 2 new webhooks, toolchain.installing and toolchain.installed, which emit when a toolchain WASM plugin is installing a tool (via proto).

What's next?

Now that are action graph supports plugins, we can take the next step in migrating an existing platform into a toolchain.

• Migrate the Rust toolchain to a WASM plugin.
• Investigate a new args/command line parser.
• Add Poetry support for the Python toolchain.