Support repository name mappings in extension_metadata

[malt3]

Allow root_module_direct_deps and root_module_direct_dev_deps to accept dicts mapping module-local names to extension-exported names, in addition to the existing list format. This enables modules to import repositories under different names than those created by the extension.

When specified as a dict (e.g., {"my_foo": "ext_foo"}), bazel mod tidy will generate use_repo commands with the mapping syntax (my_foo = "ext_foo").

Context: https://bazelbuild.slack.com/archives/C09E58X3AQ7/p1764934858912079

Stacked on https://github.com/bazelbuild/buildtools/pull/1427. I'll add some more tests in mod_command_test.py once the buildozer change is merged and available for bazel mod tidy.

RELNOTES: module_ctx.extension_metadata now accepts dictionary mappings in the root_module_direct_deps and root_module_direct_dev_deps parameters. Keys are the module‑local repository names and values are the names exported by the extension. When such a mapping is provided, bazel mod tidy generates use_repo calls with the mapping syntax (e.g., my_foo = "ext_foo"), letting modules import an extension’s repositories under custom local names.

[gemini-code-assist[bot]]

Summary of Changes

Hello @malt3, I'm Gemini Code Assist[^1]! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances Bazel's Bzlmod system by introducing support for flexible repository name mappings within module extension metadata. It allows module extensions to define how their exported repositories are named when imported by the root module, enabling custom local names for dependencies. This change improves the bazel mod tidy command's ability to generate precise use_repo commands, adapting to user-defined naming conventions and preventing conflicts.

Highlights

• Repository Name Mappings: The root_module_direct_deps and root_module_direct_dev_deps parameters in extension_metadata now support dictionary inputs, allowing modules to import repositories under different names than those exported by the extension.
• Flexible use_repo Generation: When dictionaries are used for dependency declarations, bazel mod tidy will generate use_repo commands with the mapping syntax (e.g., my_foo = "ext_foo"), providing greater control over module-local repository names.
• Enhanced Validation: Validation logic has been updated to correctly handle dictionary mappings, ensuring disjointness of both module-local names and extension-exported names between direct and dev dependencies, and validating repository names for both keys and values in the dictionary.

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[malt3]

/gemini review

[malt3]

/gemini review

[malt3]

/gemini review

[malt3]

/gemini review

[malt3]

@Wyverald and @meteorcloudy if we all agree that this is a good idea, could we get some help to get the buildozer PR merged and released so that this can still make it in time for Bazel 9?

As @fmeum mentioned, this can help solve many of the reasons why people would want isolated extensions (and subsequently could potentially allow us to get rid of true isolated extensions).

[fmeum]

@bazel-io fork 9.0.0