Rules for creating conda environments in Bazel 💚

For more info see the docs or the example.

rules_conda don't have any strict requirements by themselves.

Just make sure you are able to use conda.

Add this to your WORKSPACE file:

load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")

http_archive(
    name = "rules_conda",
    sha256 = "c5ad3a077bddff381790d64dd9cc1516b8133c1d695eb3eff4fed04a39dc4522",
    url = "https://github.com/spietras/rules_conda/releases/download/0.0.6/rules_conda-0.0.6.zip"
)

load("@rules_conda//:defs.bzl", "conda_create", "load_conda", "register_toolchain")

load_conda(
    quiet = False,  # use True to hide conda output
    version = "4.10.3",  # optional, defaults to 4.10.3
)

conda_create(
    name = "my_env",
    timeout = 600,  # each execute action can take up to 600 seconds
    clean = False,  # use True if you want to clean conda cache (less space taken, but slower subsequent builds)
    environment = "@//:environment.yml",  # label pointing to environment.yml file
    quiet = False,  # use True to hide conda output
)

register_toolchain(
    py3_env = "my_env",
)

After that, all Python targets will use the environments specified in register_toolchain.

These rules allow you to download and install conda, create conda environments and register Python toolchain from environments. This means you can achieve truly reproducible and hermetic local python environments.

Pros:

• easy to use
• no existing conda installation necessary
• no global conda installation, no global PATH modifications
• virtually impossible to corrupt your environment by mistake as it always reflects your environment.yml
• all Python targets will implicitly have access to the whole environment (the one registered in toolchain)

Cons:

• every time you update your environment configuration in environment.yml, the whole environment will be recreated from scratch (but cached package data can be reused)
• on Windows you need to add environment location to PATH or set CONDA_DLL_SEARCH_MODIFICATION_ENABLE=1 during runtime, so DLLs can be loaded properly (more on that here)

So I think these rules suit you if:

• you want to use Bazel (e.g. you fell into Python monorepo trap)
• you want to use conda for Python environment management
• you don't want to set up your Python environment manually or want your Python targets to just work on clean systems
• you are okay with environments being recreated every time something changes