fix: Obtain default Python version for Python hub repo from versions.bzl file

[gfringeli]

Issue

rules_python 1.0.0 removes the DEFAULT_PYTHON_VERSION constant from the Python hub repo's interpreters.bzl file. Instead, the version must be read from the versions.bzl file, introduced in rules_python 0.37.0.

As a result, creating a Python environment with rules_pycross (main branch) and rules_python 1.0.0 leads to the following error.

INFO: Repository rules_pycross++environments+pycross_environments_myproject instantiated at:
  <builtin>: in <toplevel>
Repository rule pycross_environments_repo defined at:
  /private/var/tmp/_bazel_gabriel/17eb730aec70ae18dde0e6ba1d906dff/external/rules_pycross+/pycross/private/toolchain_helpers.bzl:430:44: in <toplevel>
ERROR: /private/var/tmp/_bazel_gabriel/17eb730aec70ae18dde0e6ba1d906dff/external/rules_pycross+/pycross/private/toolchain_helpers.bzl:221:9: An error occurred during the fetch of repository 'rules_pycross++environments+pycross_environments_myproject':
   Traceback (most recent call last):
        File "/private/var/tmp/_bazel_gabriel/17eb730aec70ae18dde0e6ba1d906dff/external/rules_pycross+/pycross/private/toolchain_helpers.bzl", line 390, column 44, in _pycross_environment_repo_impl
                version_info = _get_python_version_info(rctx)
        File "/private/var/tmp/_bazel_gabriel/17eb730aec70ae18dde0e6ba1d906dff/external/rules_pycross+/pycross/private/toolchain_helpers.bzl", line 350, column 65, in _get_python_version_info
                default_version = _get_default_python_version_bzlmod(rctx, rctx.attr.pythons_hub_repo)
        File "/private/var/tmp/_bazel_gabriel/17eb730aec70ae18dde0e6ba1d906dff/external/rules_pycross+/pycross/private/toolchain_helpers.bzl", line 221, column 9, in _get_default_python_version_bzlmod
                fail("Unable to determine default version for python hub repo '{}'".format(pythons_hub_repo))
Error in fail: Unable to determine default version for python hub repo '@@rules_python++python+pythons_hub//:pythons_hub'
ERROR: Error loading '@@rules_pycross+//pycross/extensions:lock_repos.bzl' for module extensions, requested by /Users/gabriel/Desktop/projects/myproject/MODULE.bazel:49:27: at /private/var/tmp/_bazel_gabriel/17eb730aec70ae18dde0e6ba1d906dff/external/rules_pycross+/pycross/extensions/lock_repos.bzl:3:6: at /private/var/tmp/_bazel_gabriel/17eb730aec70ae18dde0e6ba1d906dff/external/rules_pycross+/pycross/private/bzlmod/lock_repos.bzl:5:6: Encountered error while reading extension file 'locks.bzl': no such package '@@rules_pycross++lock_import+lock_import_repos_hub//': no such package '@@rules_pycross++environments+pycross_environments_myproject//': Unable to determine default version for python hub repo '@@rules_python++python+pythons_hub//:pythons_hub': at /private/var/tmp/_bazel_gabriel/17eb730aec70ae18dde0e6ba1d906dff/external/rules_pycross+/pycross/extensions/lock_repos.bzl:3:6: at /private/var/tmp/_bazel_gabriel/17eb730aec70ae18dde0e6ba1d906dff/external/rules_pycross+/pycross/private/bzlmod/lock_repos.bzl:5:6: Encountered error while reading extension file 'locks.bzl': no such package '@@rules_pycross++lock_import+lock_import_repos_hub//': no such package '@@rules_pycross++environments+pycross_environments_myproject//': Unable to determine default version for python hub repo '@@rules_python++python+pythons_hub//:pythons_hub'
INFO: Elapsed time: 2.988s
INFO: 0 processes.
ERROR: Build did NOT complete successfully
FAILED: 
    Fetching module extension lock_import in @@rules_pycross+//pycross/extensions:lock_import.bzl; starting

Solution

Read default Python version from versions.bzl file, if it exists, and fall back to interpreters.bzl otherwise.

[jvolkman]

Thank you!

[blockjon-dd]

I'd like to use this. Could this be published to the central registry?

[betaboon]

I'd like to use this. Could this be published to the central registry?

until released you can use an override:

git_override(
    module_name = "rules_pycross",
    commit = "20fba49f17655c45f51e1bc293a329c8e1785abf",
    remote = "https://github.com/jvolkman/rules_pycross",
)