feat(extensions): Custom Rule Source Provider

[JamyDev]

The CustomRuleSourceConfig extension point allows plugins to specify which attributes contain sources for custom rule types. This is useful when you have custom Bazel rules that have custom source attributes beyond the standard srcs (as per #8140

Checklist

• I have filed an issue about this change and discussed potential changes with the maintainers.
• I have received the approval from the maintainers to make this change.
• This is not a stylistic, refactoring, or cleanup change.

Discussion thread for this change

Issue number: #8140

Description of this change

• Modifies (cc|java|python)_info aspect templates to support code generator
• Adds CUSTOM_RULE_SOURCES to code_generator_info.bzl
• Adds CustomRuleSources extension point that lets external plugin provide the getSourceAttributes value.
  • This value gets used in aspect/intellij_info_impl.bzl to provide the updated sources, then passes that to the relevant ide_info struct.

[gemini-code-assist]

Summary of Changes

Hello @JamyDev, I'm Gemini Code Assist¹! 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 the Bazel plugin's ability to integrate with custom Bazel rules by providing a flexible mechanism for defining and collecting non-standard source attributes. By introducing a new extension point and updating the aspect generation logic, the IDE can now better understand and provide language support for projects utilizing custom rule types, improving the overall development experience and reducing manual configuration needs for specialized build setups.

Highlights

• New Extension Point: Introduced a new extension point, CustomRuleSourceConfig, allowing plugins to define custom source attributes for Bazel rules. This enables the IDE to correctly identify and process source files from non-standard attributes.
• Aspect Template Updates: Modified code_generator_info.bzl to include a CUSTOM_RULE_SOURCES struct, which stores configurations for custom rule source attributes. intellij_info_impl.bzl now uses this information to collect sources and populate language-specific IDE info (Go, Python, C/C++).
• Documentation: Added comprehensive documentation (docs/extension_points/custom_rule_source.md) explaining how to implement and register CustomRuleSourceConfig extensions, including examples for custom Go rules.

Changelog

• aspect/cc_info.bzl
  • Adjusted indentation for template include blocks.
• aspect/code_generator_info.bzl
  • Added CUSTOM_RULE_SOURCES struct to hold custom rule source configurations.
  • Introduced get_custom_rule_source_config function to retrieve configurations by rule kind.
• aspect/intellij_info_impl.bzl
  • Imported CcInfoCompat and get_custom_rule_source_config.
  • Added collect_custom_rule_info function to process custom rule sources based on configurations.
  • Integrated collect_custom_rule_info into the main intellij_info_aspect_impl to handle custom rule source collection.
• aspect/java_info.bzl
  • Adjusted indentation for template include blocks.
• aspect/python_info.bzl
  • Adjusted indentation for template include blocks.
• aspect/scala_info.bzl
  • Adjusted indentation for template include blocks.
• base/src/META-INF/blaze-base.xml
  • Registered the new com.google.idea.blaze.CustomRuleSourceConfig extension point.
• base/src/com/google/idea/blaze/base/sync/aspects/CustomRuleSourceConfig.java
  • Added new interface CustomRuleSourceConfig for defining custom rule source attributes, including methods for getRuleKind, getLanguageClass, and getSourceAttributes.
• base/src/com/google/idea/blaze/base/sync/aspects/storage/AspectTemplateWriter.kt
  • Imported CustomRuleSourceConfig.
  • Modified to collect all registered CustomRuleSourceConfig extensions.
  • Passed customRuleSourceConfigs to the code_generator_info.bzl template for dynamic generation.
  • Added CustomRuleSourceConfigInfo data class to model custom rule source configurations for template generation.
• docs/extension_points/custom_rule_source.md
  • Added new documentation file detailing the CustomRuleSourceConfig extension point.
  • Provided an overview, how-to guide, example for custom Go rules, supported languages, and implementation details.

Activity

• The author has filed an issue (Support gen2gen Rules (CustomRuleSourceConfig, ArtifactLocationTransformer) #8140) and discussed potential changes with maintainers, indicating a planned and collaborative approach to this feature.
• The pull request introduces a new feature, not a stylistic, refactoring, or cleanup change, aligning with the project's development goals.
• The changes aim to support custom Bazel rules with non-standard source attributes, directly addressing the problem outlined in issue Support gen2gen Rules (CustomRuleSourceConfig, ArtifactLocationTransformer) #8140.

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[gemini-code-assist]

Code Review

This pull request introduces a new extension point CustomRuleSourceConfig to allow plugins to specify source attributes for custom Bazel rules. This is a great feature for improving IDE support. The implementation looks mostly good, with new extension points in Java, updates to aspect template writers in Kotlin, and new documentation.

However, I've found a couple of critical issues in the Starlark aspect implementation (intellij_info_impl.bzl). The logic for collecting sources from custom attributes doesn't handle single-item attributes, and more importantly, the ide_info data structures created for custom rules are inconsistent with the existing ones, which will likely break parsing on the IDE side. I've provided suggestions to fix these issues.