fix(bzlmod): let workspace-invoked python_register_toolchains to register toolchains

CHANGELOG.md

@@ -47,6 +47,9 @@ A brief description of the categories of changes:
 * (rules) `compile_pip_requirements` passes `env` to the `X.update` target (and
   not only to the `X_test` target, a bug introduced in
   [#1067](https://github.com/bazelbuild/rules_python/pull/1067)).
+* (bzlmod) In hybrid bzlmod with WORKSPACE builds,
+  `python_register_toolchains(register_toolchains=True)` is respected
+  ([#1675](https://github.com/bazelbuild/rules_python/issues/1675)).
 
 ### Added
 * (py_wheel) Now supports `compress = (True|False)` to allow disabling

python/private/BUILD.bazel

@@ -177,7 +177,6 @@ bzl_library(
     deps = [
         ":auth_bzl",
         ":bazel_tools_bzl",
-        ":bzlmod_enabled_bzl",
         ":coverage_deps_bzl",
         ":full_version_bzl",
         ":internal_config_repo_bzl",

python/private/python.bzl

@@ -228,7 +228,11 @@ def _python_impl(module_ctx):
         kwargs.update(py.config.kwargs.get(toolchain_info.python_version, {}))
         kwargs.update(py.config.kwargs.get(full_python_version, {}))
         kwargs.update(py.config.default)
-        python_register_toolchains(name = toolchain_info.name, **kwargs)
+        python_register_toolchains(
+            name = toolchain_info.name,
+            _internal_bzlmod_toolchain_call = True,
+            **kwargs
+        )
 
     # Create the pythons_hub repo for the interpreter meta data and the
     # the various toolchains.

python/private/python_register_toolchains.bzl

@@ -23,7 +23,6 @@ load(
     "TOOL_VERSIONS",
     "get_release_info",
 )
-load(":bzlmod_enabled.bzl", "BZLMOD_ENABLED")
 load(":coverage_deps.bzl", "coverage_dep")
 load(":full_version.bzl", "full_version")
 load(":python_repository.bzl", "python_repository")
@@ -75,9 +74,8 @@ def python_register_toolchains(
             version.
         **kwargs: passed to each {obj}`python_repository` call.
     """
-
-    if BZLMOD_ENABLED:
-        # you cannot used native.register_toolchains when using bzlmod.
+    bzlmod_toolchain_call = kwargs.pop("_internal_bzlmod_toolchain_call", False)
+    if bzlmod_toolchain_call:
         register_toolchains = False
 
     base_url = kwargs.pop("base_url", DEFAULT_RELEASE_BASE_URL)
@@ -169,7 +167,7 @@ def python_register_toolchains(
     )
 
     # in bzlmod we write out our own toolchain repos
-    if BZLMOD_ENABLED:
+    if bzlmod_toolchain_call:
         return
 
     toolchains_repo(