moon v1.30 - Python support, self-hosted remote caching, task graph, and more!

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It's been almost 2 months since our last release, and we're excited to announce some major features requested by the community!

Experimental Python tier 2 and 3 support

Thanks to a contribution from @harlequin, we now provide Python tier 2 and 3 support. Python is a very popular language, so it was about time that we officially supported it in some capacity. When enabling Python in moon, the following functionality will be enabled:

• Will download and install Python into the toolchain (if python.version is defined).
• Will parse requirements.txt to extract dependency and version information for hashing.
• Will automatically activate virtual environments and setup PATH for tasks.
• Will automatically install dependencies for requirements.txt via pip.
• And a handful of internal interoperability features.

However, we're still marking this implementation as experimental, as it hasn't been thoroughly tested, and we're not 100% positive the workflows are what users expect. So please provide any feedback, good or bad!

Furthermore, as mentioned above, we install dependencies with pip (the version of pip that comes pre-installed with the current Python version). At this time, we do not support other package managers like Poetry, Hatch, PDM, Rye, or uv, but we will in the future!

New python configurations

Languages in moon are enabled through configuration blocks in .moon/toolchain.yml, and Python is no different. We now support a python toolchain setting (view all available settings).

python:
  version: '3.14.0'

When the python setting is defined, it will enable the language and deep platform integration, and when the python.version field is defined, it will further enable toolchain support. Both of these features provide heavy automation, improving the overall developer experience.

This is fantastic, but what if another Python project in the monorepo requires a different toolchain channel/version? If so, they can use the new toolchain.python setting in moon.yml to define project-level overrides.

toolchain:
  python:
    version: '3.12.0'

Built-in virtual environments

Of course we also have support for Python virtual environments. When running a task, moon will automatically enable the virtual environment in the workspace root or a project root (depending on config)! The name of the venv can be customized with the python.venvName setting, otherwise it defaults to .venv.

python:
  venvName: '.venvcustom'

Unstable self-hosted remote caching

This has been a request from the community for a very long time, and we get it, not every user wants to store their build artifacts (not source code) in a third-party cloud provider. While we're proud of our moonbase service, it wasn't a viable option for many companies because of their proprietary requirements. We spent a few months reworking moonbase to work as a self-hosted service, so users can host it as on-prem solution, but it has been a very costly initiative. During this process, we came to the conclusion that spending our time and resources on moonbase simply isn't worth it, so we made the hard decision to sunset moonbase in the future.

So what does that mean for remote caching? Simply put, you can now host your own remote caching service! Instead of building a custom API for consumers to implement, we opted to implement the Bazel Remote Execution API, which supports a content addressable storage (CAS) API, and is used by other popular build tools, like Bazel, Buck, Pants, and more!

Because we opted for a community solution, we can now focus all our efforts on moon and proto! Additionally, adopting RE API allows you, the user, to use an off-the-shelf solution, like bazel-remote, instead of building your own custom caching server! For example, to make use of remote caching, simply serve bazel-remote:

bazel-remote --dir /path/to/moon-cache --max_size 10 --storage_mode uncompressed --grpc_address 0.0.0.0:9092

And then configure the new unstable_remote setting in .moon/workspace.yml.

unstable_remote:
  host: 'grpc://your-host.com:9092'

Pretty awesome right? Jump to the official remote caching documentation for more information on this implementation.

Unsupported features

Since this is a new feature, we're marking it as unstable, as it hasn't been thoroughly tested, and does not support the entire Bazel RE API. The following features have not been implemented, but will be in the future.

• HTTP(S) host (we only support gRPC(S))
• Digest hashing functions besides SHA256
• Compression formats (we only support identity/uncompressed right now)
• Write/read bytestream for large blobs (4mb is the current limit)
• Better TLS/mTLS support (it has some issues)
• Directory blob types

New task graph and improved affected tracker

In our last release, we announced a new affected tracker for projects, but not for tasks. The reason behind this was simple, we couldn't! Up until now, we had no concept of a task graph, we had a project graph (that had tasks) and an action graph (that ran tasks), but the relationships between tasks were split across both of these graphs.

This made it complicated to support tasks for the new affected tracker, as the action graph consumes the tracker, not the other way around. To remedy this issue, we now support an official task graph, which is derived from the project graph, and then feeds into the action graph. Since the task graph sits outside of the action graph, we're now able to support tasks in the affected tracker!

Because of the new task graph, the following improvements have been introduced:

• Tasks are now supported in the affected tracker (as mentioned).
• We can now properly query dependencies and dependents of specific tasks.
• We can now associate types to relationships (graph edges). For example, in the future we can add optional, cleanup, and other kinds of dependencies.
• We've added a new command, moon task-graph, that can visualize tasks in isolation.
• We've updated the moon query tasks to derive information from the task graph.

Other changes

View the official release for a full list of changes.

• Added basic support for Git submodules, and will now extract touched files from all submodules.
• Added 7 new token variables: $arch, $os, $osFamily, $vcsBranch, $vcsRepository, $vcsRevision, $workingDir
• Added a rust.binstallVersion setting to .moon/toolchain.yml.
• Updated Pkl configurations to support read() for environment variables.