[aignas]

Extract each wheel that is downloaded by the Bazel downloader once and reuse
the extracted repository across Python versions and hub repositories.

Before this change each whl_library repository downloaded and extracted the
wheel, so a pure Python wheel used by 5 Python versions was extracted 5 times.
Now each unique (URL, filename, integrity) combination is extracted once into a
whl_<name>_<version>_<tags> repository, and the original whl_library
repository names become whl_deps_repo repositories that read the METADATA
from the extracted repository and wire the dependencies for the hub. The hub
repositories still point to the same repository names.

Details:

• The download arguments (index_url, envsubst, netrc, auth_patterns)
  are taken from the first registration of the wheel. The URLs are compared
  using the unresolved index_url, so the credentials that envsubst may
  inject never end up in the repository arguments.
• If the same wheel is extracted with different arguments (e.g.
  pip_data_exclude), then the later registrations fall back to a regular
  whl_library.
• Wheels with whl_patches, annotations (whl_modifications) or
  extra_hub_aliases are not shared, because the extra targets would not be
  available in the whl_deps_repo.
• whl_deps_repo now also aliases the srcs and whl_file targets that the
  hub references.
• The resolved experimental_index_url is no longer passed to
  simpleapi_download and whl_library, only the unresolved template is.

Fixes #2948
Work towards #2530

[gemini-code-assist]

Code Review

This pull request implements an optimized mode for whl_library (gated by the RULES_PYTHON_WHL_LIBRARY_OPTIMIZED environment variable) to allow wheel reuse across different Python versions by omitting the Python version from spoke repository names, generating per-extra targets, and creating explicit aliases in the hub repository. The code review identified several critical issues with this implementation: static aliases in render_pkg_aliases.bzl break multi-version/multi-platform setups, and iterating over extras_info causes aliases to overwrite each other. Additionally, a naming mismatch in extension.bzl between the unified hub alias and the hub repository package name will result in broken aliases, and skipping pkg__extra target generation when there are no extra dependencies leads to build failures.

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[gemini-code-assist]

The _render_extra_alias function generates a static alias pointing to a single spoke repository. However, in a multi-version or multi-platform setup, there are multiple spoke repositories. We should replace this with a multiplatform alias generator that uses select to choose the correct spoke repository based on the active configuration.

def _render_extra_alias_multiplatform(*, name, repo_mapping, target_suffix):
    if type(repo_mapping) == type(""):
        actual_expr = repr("@{}//:{}".format(repo_mapping, target_suffix))
        load_statement = ""
    else:
        actual_dict = {}
        for config_setting, repo_name in repo_mapping.items():
            key = _repr_config_setting(config_setting)
            actual_dict[key] = repr("@{}//:{}".format(repo_name, target_suffix))

        if len(actual_dict) == 1 and list(actual_dict.keys())[0] == repr("//conditions:default"):
            actual_expr = list(actual_dict.values())[0]
        else:
            sorted_pairs = sorted(actual_dict.items())
            actual_expr = "select({\n"
            for k, v in sorted_pairs:
                actual_expr += "        {}: {},\n".format(k, v)
            actual_expr += "    })"

        needs_load = any(["whl_config_setting" in k for k in actual_dict.keys()])
        load_statement = ""
        if needs_load:
            load_statement = 'load("@rules_python//python/private/pypi:whl_config_setting.bzl", "whl_config_setting")\n'

    return """\
{load_statement}package(default_visibility = ["//visibility:public"])

alias(
    name = "pkg",
    actual = {actual_expr},
)

alias(
    name = "whl",
    actual = {actual_expr},
)
""".format(
        load_statement = load_statement,
        actual_expr = actual_expr,
    )

[gemini-code-assist]

In a multi-version or multi-platform setup, whl_extras contains multiple spoke repositories for the same wheel. Iterating over extras_info.items() and writing directly to files causes the alias for one spoke to overwrite the others, breaking multi-version/multi-platform support for extras. We should use the multiplatform alias generator to create a single select-based alias that correctly routes to the appropriate spoke repository.

    # Generate extra alias directories for optimized mode extras.
    for name, extras_info in whl_extras.items():
        normalized = normalize_name(name)
        pkg_aliases = aliases.get(normalized)
        if not pkg_aliases:
            continue

        # Find all unique extras across all repos for this wheel
        unique_extras = {}
        for extra_names in extras_info.values():
            for extra in extra_names:
                unique_extras[extra] = True

        for extra in unique_extras:
            extra_pkg = "{}_{}".format(normalized, extra)
            files["{}/BUILD.bazel".format(extra_pkg)] = _render_extra_alias_multiplatform(
                name = extra_pkg,
                repo_mapping = pkg_aliases,
                target_suffix = "{}__{}".format(normalized, extra),
            )

        # Also create pkg__ alias (no extras)
        no_extras_pkg = "{}__".format(normalized)
        files["{}/BUILD.bazel".format(no_extras_pkg)] = _render_extra_alias_multiplatform(
            name = no_extras_pkg,
            repo_mapping = pkg_aliases,
            target_suffix = normalized,
        )

[gemini-code-assist]

There is a naming mismatch between the unified hub alias name and the hub repository package name. The unified hub alias is generated with double underscores __ (e.g., requests__security), whereas render_pkg_aliases.bzl generates the hub repository package with a single underscore _ (e.g., requests_security). This mismatch will cause the unified hub aliases to point to non-existent packages. Update this to use a single underscore to match the hub repository package naming.

Suggested change

	alias_name = "%s__%s" % (norm_pkg, extra)
	alias_name = "%s_%s" % (norm_pkg, extra)

[gemini-code-assist]

Skipping the generation of the pkg__extra target when there are no extra dependencies (or when all extra dependencies are already present in the base dependencies) will cause the hub repository's alias to point to a non-existent target, leading to build failures. We should always generate the pkg__extra target, even if it only depends on ":pkg", to ensure that the hub aliases remain valid.

[rickeylev]

saw this was draft, so didn't look too thoroughly, just for things that looked like the bot was obviously wrong

[aignas]

Again, ran out of free tokens, so will postpone for another day.

[aignas]

• 2 types of whl_library repos - one with extracted files, one wiring the deps.

[aignas]

So it seems that it is much better to just separate the repositories - one with extracted whl sources, one with the parsed METADATA. This way the change is surgical and very easy to reason about. This was spiked by hand and then vibed and debugged. The build should work but there are many things missing.

TODO:

• split the new repo into a separate file.
• Create a separate function for the BUILD.bazel file generation and add unit tests.
• Update existing hub_builder.bzl unit tests.
• Remove the confabulated "fixes" to make the code easier to read.

[rickeylev]

/review

[aignas]

This should now work.

EDIT: just realized that merging main into this branch should not have affected it.

[aignas]

/review

[aignas]

Given the recent refactors, I've did it again in a more surgical way.