fix: load target_platforms through the hub

CHANGELOG.md

@@ -105,6 +105,13 @@ END_UNRELEASED_TEMPLATE
   [PR #2746](https://github.com/bazel-contrib/rules_python/pull/2746).
 * (rules) {attr}`py_binary.srcs` and {attr}`py_test.srcs` is no longer mandatory when
   `main_module` is specified (for `--bootstrap_impl=script`)
+* (pypi) From now on the `Requires-Dist` from the wheel metadata is analysed in
+  the loading phase instead of repository rule phase giving better caching
+  performance when the target platforms are changed (e.g. target python
+  versions). This is preparatory work for stabilizing the cross-platform wheel
+  support. From now on the usage of `experimental_target_platforms` should be
+  avoided and the `requirements_by_platform` values should be instead used to
+  specify the target platforms for the given dependencies.
 
 [20250317]: https://github.com/astral-sh/python-build-standalone/releases/tag/20250317
 

python/private/pypi/BUILD.bazel

@@ -212,15 +212,6 @@ bzl_library(
     ],
 )
 
-bzl_library(
-    name = "pep508_bzl",
-    srcs = ["pep508.bzl"],
-    deps = [
-        ":pep508_env_bzl",
-        ":pep508_evaluate_bzl",
-    ],
-)
-
 bzl_library(
     name = "pep508_deps_bzl",
     srcs = ["pep508_deps.bzl"],
@@ -378,13 +369,12 @@ bzl_library(
         ":attrs_bzl",
         ":deps_bzl",
         ":generate_whl_library_build_bazel_bzl",
-        ":parse_whl_name_bzl",
         ":patch_whl_bzl",
-        ":pep508_deps_bzl",
+        ":pep508_requirement_bzl",
         ":pypi_repo_utils_bzl",
         ":whl_metadata_bzl",
-        ":whl_target_platforms_bzl",
         "//python/private:auth_bzl",
+        "//python/private:bzlmod_enabled_bzl",
         "//python/private:envsubst_bzl",
         "//python/private:is_standalone_interpreter_bzl",
         "//python/private:repo_utils_bzl",

python/private/pypi/attrs.bzl

@@ -123,6 +123,9 @@ Warning:
     "experimental_target_platforms": attr.string_list(
         default = [],
         doc = """\
+*NOTE*: This will be removed in the next major version, so please consider migrating
+to `bzlmod` and rely on {attr}`pip.parse.requirements_by_platform` for this feature.
+
 A list of platforms that we will generate the conditional dependency graph for
 cross platform wheels by parsing the wheel metadata. This will generate the
 correct dependencies for packages like `sphinx` or `pylint`, which include

python/private/pypi/config.bzl.tmpl.bzlmod

@@ -0,0 +1,9 @@
+"""Extra configuration values that are exposed from the hub repository for spoke repositories to access.
+
+NOTE: This is internal `rules_python` API and if you would like to depend on it, please raise an issue
+with your usecase. This may change in between rules_python versions without any notice.
+
+@generated by rules_python pip.parse bzlmod extension.
+"""
+
+target_platforms = %%TARGET_PLATFORMS%%

python/private/pypi/extension.bzl

@@ -32,7 +32,6 @@ load(":simpleapi_download.bzl", "simpleapi_download")
 load(":whl_config_setting.bzl", "whl_config_setting")
 load(":whl_library.bzl", "whl_library")
 load(":whl_repo_name.bzl", "pypi_repo_name", "whl_repo_name")
-load(":whl_target_platforms.bzl", "whl_target_platforms")
 
 def _major_minor_version(version):
     version = semver(version)
@@ -68,7 +67,6 @@ def _create_whl_repos(
         *,
         pip_attr,
         whl_overrides,
-        evaluate_markers = evaluate_markers,
         available_interpreters = INTERPRETER_LABELS,
         get_index_urls = None):
     """create all of the whl repositories
@@ -77,7 +75,6 @@ def _create_whl_repos(
         module_ctx: {type}`module_ctx`.
         pip_attr: {type}`struct` - the struct that comes from the tag class iteration.
         whl_overrides: {type}`dict[str, struct]` - per-wheel overrides.
-        evaluate_markers: the function to use to evaluate markers.
         get_index_urls: A function used to get the index URLs
         available_interpreters: {type}`dict[str, Label]` The dictionary of available
             interpreters that have been registered using the `python` bzlmod extension.
@@ -162,14 +159,12 @@ def _create_whl_repos(
             requirements_osx = pip_attr.requirements_darwin,
             requirements_windows = pip_attr.requirements_windows,
             extra_pip_args = pip_attr.extra_pip_args,
+            # TODO @aignas 2025-04-15: pass the full version into here
             python_version = major_minor,
             logger = logger,
         ),
         extra_pip_args = pip_attr.extra_pip_args,
         get_index_urls = get_index_urls,
-        # NOTE @aignas 2025-02-24: we will use the "cp3xx_os_arch" platform labels
-        # for converting to the PEP508 environment and will evaluate them in starlark
-        # without involving the interpreter at all.
         evaluate_markers = evaluate_markers,
         logger = logger,
     )
@@ -191,7 +186,6 @@ def _create_whl_repos(
             enable_implicit_namespace_pkgs = pip_attr.enable_implicit_namespace_pkgs,
             environment = pip_attr.environment,
             envsubst = pip_attr.envsubst,
-            experimental_target_platforms = pip_attr.experimental_target_platforms,
             group_deps = group_deps,
             group_name = group_name,
             pip_data_exclude = pip_attr.pip_data_exclude,
@@ -244,6 +238,12 @@ def _create_whl_repos(
         },
         extra_aliases = extra_aliases,
         whl_libraries = whl_libraries,
+        target_platforms = {
+            plat: None
+            for reqs in requirements_by_platform.values()
+            for req in reqs
+            for plat in req.target_platforms
+        },
     )
 
 def _whl_repos(*, requirement, whl_library_args, download_only, netrc, auth_patterns, multiple_requirements_for_whl = False, python_version):
@@ -274,20 +274,11 @@ def _whl_repos(*, requirement, whl_library_args, download_only, netrc, auth_patt
         args["urls"] = [distribution.url]
         args["sha256"] = distribution.sha256
         args["filename"] = distribution.filename
-        args["experimental_target_platforms"] = requirement.target_platforms
 
         # Pure python wheels or sdists may need to have a platform here
         target_platforms = None
         if distribution.filename.endswith(".whl") and not distribution.filename.endswith("-any.whl"):
-            parsed_whl = parse_whl_name(distribution.filename)
-            whl_platforms = whl_target_platforms(
-                platform_tag = parsed_whl.platform_tag,
-            )
-            args["experimental_target_platforms"] = [
-                p
-                for p in requirement.target_platforms
-                if [None for wp in whl_platforms if p.endswith(wp.target_platform)]
-            ]
+            pass
         elif multiple_requirements_for_whl:
             target_platforms = requirement.target_platforms
 
@@ -416,6 +407,7 @@ You cannot use both the additive_build_content and additive_build_content_file a
     hub_group_map = {}
     exposed_packages = {}
     extra_aliases = {}
+    target_platforms = {}
     whl_libraries = {}
 
     for mod in module_ctx.modules:
@@ -498,6 +490,7 @@ You cannot use both the additive_build_content and additive_build_content_file a
             for whl_name, aliases in out.extra_aliases.items():
                 extra_aliases[hub_name].setdefault(whl_name, {}).update(aliases)
             exposed_packages.setdefault(hub_name, {}).update(out.exposed_packages)
+            target_platforms.setdefault(hub_name, {}).update(out.target_platforms)
             whl_libraries.update(out.whl_libraries)
 
             # TODO @aignas 2024-04-05: how do we support different requirement
@@ -535,6 +528,10 @@ You cannot use both the additive_build_content and additive_build_content_file a
             }
             for hub_name, extra_whl_aliases in extra_aliases.items()
         },
+        target_platforms = {
+            hub_name: sorted(p)
+            for hub_name, p in target_platforms.items()
+        },
         whl_libraries = {
             k: dict(sorted(args.items()))
             for k, args in sorted(whl_libraries.items())
@@ -626,15 +623,13 @@ def _pip_impl(module_ctx):
             },
             packages = mods.exposed_packages.get(hub_name, []),
             groups = mods.hub_group_map.get(hub_name),
+            target_platforms = mods.target_platforms.get(hub_name, []),
         )
 
     if bazel_features.external_deps.extension_metadata_has_reproducible:
-        # If we are not using the `experimental_index_url feature, the extension is fully
-        # deterministic and we don't need to create a lock entry for it.
-        #
-        # In order to be able to dogfood the `experimental_index_url` feature before it gets
-        # stabilized, we have created the `_pip_non_reproducible` function, that will result
-        # in extra entries in the lock file.
+        # NOTE @aignas 2025-04-15: this is set to be reproducible, because the
+        # results after calling the PyPI index should be reproducible on each
+        # machine.
         return module_ctx.extension_metadata(reproducible = True)
     else:
         return None

python/private/pypi/generate_whl_library_build_bazel.bzl

@@ -21,42 +21,56 @@ _RENDER = {
     "copy_files": render.dict,
     "data": render.list,
     "data_exclude": render.list,
-    "dependencies": render.list,
-    "dependencies_by_platform": lambda x: render.dict(x, value_repr = render.list),
     "entry_points": render.dict,
+    "extras": render.list,
     "group_deps": render.list,
+    "requires_dist": render.list,
     "srcs_exclude": render.list,
-    "tags": render.list,
+    "target_platforms": lambda x: render.list(x) if x else "target_platforms",
 }
 
 # NOTE @aignas 2024-10-25: We have to keep this so that files in
 # this repository can be publicly visible without the need for
 # export_files
 _TEMPLATE = """\
-load("@rules_python//python/private/pypi:whl_library_targets.bzl", "whl_library_targets")
+{loads}
 
 package(default_visibility = ["//visibility:public"])
 
-whl_library_targets(
+whl_library_targets_from_requires(
 {kwargs}
 )
 """
 
 def generate_whl_library_build_bazel(
         *,
         annotation = None,
+        default_python_version = None,
         **kwargs):
     """Generate a BUILD file for an unzipped Wheel
 
     Args:
         annotation: The annotation for the build file.
+        default_python_version: The python version to use to parse the METADATA.
         **kwargs: Extra args serialized to be passed to the
             {obj}`whl_library_targets`.
 
     Returns:
         A complete BUILD file as a string
     """
 
+    loads = [
+        """load("@rules_python//python/private/pypi:whl_library_targets.bzl", "whl_library_targets_from_requires")""",
+    ]
+    if not kwargs.setdefault("target_platforms", None):
+        dep_template = kwargs["dep_template"]
+        loads.append(
+            "load(\"{}\", \"{}\")".format(
+                dep_template.format(name = "", target = "config.bzl"),
+                "target_platforms",
+            ),
+        )
+
     additional_content = []
     if annotation:
         kwargs["data"] = annotation.data
@@ -66,10 +80,13 @@ def generate_whl_library_build_bazel(
         kwargs["srcs_exclude"] = annotation.srcs_exclude_glob
         if annotation.additive_build_content:
             additional_content.append(annotation.additive_build_content)
+    if default_python_version:
+        kwargs["default_python_version"] = default_python_version
 
     contents = "\n".join(
         [
             _TEMPLATE.format(
+                loads = "\n".join(loads),
                 kwargs = render.indent("\n".join([
                     "{} = {},".format(k, _RENDER.get(k, repr)(v))
                     for k, v in sorted(kwargs.items())

python/private/pypi/hub_repository.bzl

@@ -45,7 +45,14 @@ def _impl(rctx):
     macro_tmpl = "@@{name}//{{}}:{{}}".format(name = rctx.attr.name)
 
     rctx.file("BUILD.bazel", _BUILD_FILE_CONTENTS)
-    rctx.template("requirements.bzl", rctx.attr._template, substitutions = {
+    rctx.template(
+        "config.bzl",
+        rctx.attr._config_template,
+        substitutions = {
+            "%%TARGET_PLATFORMS%%": render.list(rctx.attr.target_platforms),
+        },
+    )
+    rctx.template("requirements.bzl", rctx.attr._requirements_bzl_template, substitutions = {
         "%%ALL_DATA_REQUIREMENTS%%": render.list([
             macro_tmpl.format(p, "data")
             for p in bzl_packages
@@ -80,14 +87,21 @@ The list of packages that will be exposed via all_*requirements macros. Defaults
             mandatory = True,
             doc = "The apparent name of the repo. This is needed because in bzlmod, the name attribute becomes the canonical name.",
         ),
+        "target_platforms": attr.string_list(
+            mandatory = True,
+            doc = "All of the target platforms for the hub repo",
+        ),
         "whl_map": attr.string_dict(
             mandatory = True,
             doc = """\
 The wheel map where values are json.encoded strings of the whl_map constructed
 in the pip.parse tag class.
 """,
         ),
-        "_template": attr.label(
+        "_config_template": attr.label(
+            default = ":config.bzl.tmpl.bzlmod",
+        ),
+        "_requirements_bzl_template": attr.label(
             default = ":requirements.bzl.tmpl.bzlmod",
         ),
     },