refactor(pypi): move the platform config to MODULE.bazel

MODULE.bazel

@@ -60,6 +60,62 @@ register_toolchains("@pythons_hub//:all")
 # Install twine for our own runfiles wheel publishing and allow bzlmod users to use it.
 
 pip = use_extension("//python/extensions:pip.bzl", "pip")
+
+# NOTE @aignas 2025-07-06: we define these platforms to keep backwards compatibility with the
+# current `experimental_index_url` implementation. Whilst we stabilize the API this list may be
+# updated with a mention in the CHANGELOG.
+[
+    pip.default(
+        arch_name = cpu,
+        config_settings = [
+            "@platforms//cpu:{}".format(cpu),
+            "@platforms//os:linux",
+        ],
+        env = {"platform_version": "0"},
+        os_name = "linux",
+        platform = "linux_{}".format(cpu),
+    )
+    for cpu in [
+        "x86_64",
+        "aarch64",
+        # TODO @aignas 2025-05-19: only leave tier 0-1 cpus when stabilizing the
+        # `pip.default` extension. i.e. drop the below values - users will have to
+        # define themselves if they need them.
+        "arm",
+        "ppc",
+        "s390x",
+    ]
+]
+
+[
+    pip.default(
+        arch_name = cpu,
+        config_settings = [
+            "@platforms//cpu:{}".format(cpu),
+            "@platforms//os:osx",
+        ],
+        # We choose the oldest non-EOL version at the time when we release `rules_python`.
+        # See https://endoflife.date/macos
+        env = {"platform_version": "14.0"},
+        os_name = "osx",
+        platform = "osx_{}".format(cpu),
+    )
+    for cpu in [
+        "aarch64",
+        "x86_64",
+    ]
+]
+
+pip.default(
+    arch_name = "x86_64",
+    config_settings = [
+        "@platforms//cpu:x86_64",
+        "@platforms//os:windows",
+    ],
+    env = {"platform_version": "0"},
+    os_name = "windows",
+    platform = "windows_x86_64",
+)
 pip.parse(
     # NOTE @aignas 2024-10-26: We have an integration test that depends on us
     # being able to build sdists for this hub, so explicitly set this to False.

python/private/pypi/extension.bzl

@@ -393,64 +393,6 @@ def _configure(config, *, platform, os_name, arch_name, config_settings, env = {
     else:
         config["platforms"].pop(platform)
 
-def _create_config(defaults):
-    if defaults["platforms"]:
-        return struct(**defaults)
-
-    # NOTE: We have this so that it is easier to maintain unit tests assuming certain
-    # defaults
-    for cpu in [
-        "x86_64",
-        "aarch64",
-        # TODO @aignas 2025-05-19: only leave tier 0-1 cpus when stabilizing the
-        # `pip.default` extension. i.e. drop the below values - users will have to
-        # define themselves if they need them.
-        "arm",
-        "ppc",
-        "s390x",
-    ]:
-        _configure(
-            defaults,
-            arch_name = cpu,
-            os_name = "linux",
-            platform = "linux_{}".format(cpu),
-            config_settings = [
-                "@platforms//os:linux",
-                "@platforms//cpu:{}".format(cpu),
-            ],
-            env = {"platform_version": "0"},
-        )
-    for cpu in [
-        "aarch64",
-        "x86_64",
-    ]:
-        _configure(
-            defaults,
-            arch_name = cpu,
-            # We choose the oldest non-EOL version at the time when we release `rules_python`.
-            # See https://endoflife.date/macos
-            os_name = "osx",
-            platform = "osx_{}".format(cpu),
-            config_settings = [
-                "@platforms//os:osx",
-                "@platforms//cpu:{}".format(cpu),
-            ],
-            env = {"platform_version": "14.0"},
-        )
-
-    _configure(
-        defaults,
-        arch_name = "x86_64",
-        os_name = "windows",
-        platform = "windows_x86_64",
-        config_settings = [
-            "@platforms//os:windows",
-            "@platforms//cpu:x86_64",
-        ],
-        env = {"platform_version": "0"},
-    )
-    return struct(**defaults)
-
 def parse_modules(
         module_ctx,
         _fail = fail,
@@ -527,7 +469,7 @@ You cannot use both the additive_build_content and additive_build_content_file a
                 # for what. We could also model the `cp313t` freethreaded as separate platforms.
             )
 
-    config = _create_config(defaults)
+    config = struct(**defaults)
 
     # TODO @aignas 2025-06-03: Merge override API with the builder?
     _overriden_whl_set = {}