fix(bzlmod): generate config_setting values for all python toolchains (#2350)

CHANGELOG.md

@@ -20,8 +20,11 @@ A brief description of the categories of changes:
 * Particular sub-systems are identified using parentheses, e.g. `(bzlmod)` or
   `(docs)`.
 
+{#v0-0-0}
 ## Unreleased
 
+[0.0.0]: https://github.com/bazelbuild/rules_python/releases/tag/0.0.0
+
 ### Changed
 - Nothing yet
 
@@ -34,6 +37,17 @@ A brief description of the categories of changes:
 ### Removed
 - Nothing yet
 
+{#v0-37-2}
+## [0.37.2] - 2024-10-27
+
+[0.37.2]: https://github.com/bazelbuild/rules_python/releases/tag/0.37.2
+
+{#v0-37-2-fixed}
+### Fixed
+* (bzlmod) Generate `config_setting` values for all available toolchains instead
+  of only the registered toolchains, which restores the previous behaviour that
+  `bzlmod` users would have observed.
+
 {#v0-37-1}
 ## [0.37.1] - 2024-10-22
 

examples/multi_python_versions/MODULE.bazel

@@ -30,6 +30,7 @@ python.toolchain(
 )
 use_repo(
     python,
+    "pythons_hub",
     python = "python_versions",
 )
 

examples/multi_python_versions/tests/BUILD.bazel

@@ -1,9 +1,14 @@
 load("@bazel_skylib//rules:copy_file.bzl", "copy_file")
+load("@bazel_skylib//rules:diff_test.bzl", "diff_test")
+load("@bazel_skylib//rules:write_file.bzl", "write_file")
 load("@python//3.10:defs.bzl", py_binary_3_10 = "py_binary", py_test_3_10 = "py_test")
 load("@python//3.11:defs.bzl", py_binary_3_11 = "py_binary", py_test_3_11 = "py_test")
 load("@python//3.8:defs.bzl", py_binary_3_8 = "py_binary", py_test_3_8 = "py_test")
 load("@python//3.9:defs.bzl", py_binary_3_9 = "py_binary", py_test_3_9 = "py_test")
+load("@pythons_hub//:versions.bzl", "MINOR_MAPPING", "PYTHON_VERSIONS")
 load("@rules_python//python:defs.bzl", "py_binary", "py_test")
+load("@rules_python//python:versions.bzl", DEFAULT_MINOR_MAPPING = "MINOR_MAPPING", DEFAULT_TOOL_VERSIONS = "TOOL_VERSIONS")
+load("@rules_python//python/private:text_util.bzl", "render")  # buildifier: disable=bzl-visibility
 load("@rules_shell//shell:sh_test.bzl", "sh_test")
 
 copy_file(
@@ -183,3 +188,37 @@ sh_test(
         "VERSION_PY_BINARY": "$(rootpath :version_3_10)",
     },
 )
+
+# The following test ensures that default toolchain versions are the same as in
+# the TOOL_VERSIONS array.
+
+# NOTE @aignas 2024-10-26: This test here is to do a sanity check and not
+# include extra dependencies - if rules_testing is included here, we can
+# potentially uses `rules_testing` for a more lightweight test.
+write_file(
+    name = "default_python_versions",
+    out = "default_python_versions.txt",
+    content = [
+        "MINOR_MAPPING:",
+        render.dict(dict(sorted(DEFAULT_MINOR_MAPPING.items()))),
+        "PYTHON_VERSIONS:",
+        render.list(sorted(DEFAULT_TOOL_VERSIONS)),
+    ],
+)
+
+write_file(
+    name = "pythons_hub_versions",
+    out = "pythons_hub_versions.txt",
+    content = [
+        "MINOR_MAPPING:",
+        render.dict(dict(sorted(MINOR_MAPPING.items()))),
+        "PYTHON_VERSIONS:",
+        render.list(sorted(PYTHON_VERSIONS)),
+    ],
+)
+
+diff_test(
+    name = "test_versions",
+    file1 = "default_python_versions",
+    file2 = "pythons_hub_versions",
+)

python/private/python.bzl

@@ -241,6 +241,7 @@ def _python_impl(module_ctx):
         # Last toolchain is default
         default_python_version = py.default_python_version,
         minor_mapping = py.config.minor_mapping,
+        python_versions = list(py.config.default["tool_versions"].keys()),
         toolchain_prefixes = [
             render.toolchain_prefix(index, toolchain.name, _TOOLCHAIN_INDEX_PAD_LENGTH)
             for index, toolchain in enumerate(py.toolchains)