feat: gapic centralization into api core

[hebaalazzeh]

Update and Release google-api-core

This PR introduces centralized helper functions into google.api_core.gapic_v1. The goal of this centralization is to reduce package size, improve maintainability, and boost import performance of generated GAPIC clients by moving redundant, service-agnostic boilerplate logic into google-api-core.

Key Changes

• Centralized GAPIC Helpers: Extracted logic previously repeated across generated clients into focused, domain-specific modules within google.api_core.gapic_v1:
  • _routing.py (get_default_mtls_endpoint, get_api_endpoint, get_universe_domain)
  • _client_cert.py (use_client_cert_effective, get_client_cert_source)
  • _config_helpers.py (read_environment_variables)
  • _method_helpers.py (setup_request_id)
• Public Method Exposure: Removed the _ prefix from these functions so they can be securely imported and utilized by external generated clients.
• Backward Compatibility: Added internal aliases (e.g., _use_client_cert_effective = use_client_cert_effective) to prevent breaking changes for existing GAPIC clients (over 2,400+ repos) that have not yet been regenerated.
• Comprehensive Test Coverage: Added exhaustive unit tests for all helper functions in dedicated, domain-specific test files (test_routing.py, test_client_cert.py, test_config_helpers.py, test_method_helpers.py).
• CI Environment Hardening:
  • Handled grpc optional dependencies gracefully to ensure tests pass in install_grpc=False environments.
  • Ensured older versions of google-auth (e.g. <=2.14.1) pass in the CI test matrix by safely validating should_use_client_cert availability.

Next Steps (Phase 2)

Once this PR is merged and a new minor version of google-api-core (e.g. 2.18.0) is released, we can update the GAPIC generator to utilize these centralized helpers and stop emitting the redundant logic.

Note

Full details and baseline metrics are available in the attached Design Document.

[gemini-code-assist]

Code Review

This pull request introduces a new client_helpers module in google-api-core containing helper functions for GAPIC client initialization, and adds global lazy imports control (__lazy_modules__) to google-cloud-compute. The review feedback suggests optimizing performance by compiling the mTLS endpoint regular expression at the module level rather than inside the function. Additionally, it recommends correcting the type annotations in get_api_endpoint to use Optional[Any] for client_cert_source and Optional[str] for the return type.

[hebaalazzeh]

/gemini

[ohmayr]

Could we open a draft PR for gapic-generator with the template updates, temporarily pointing its test google-api-core dependency to this git branch?

Running the gapic-generator-python CI (showcase and unit tests) on that draft PR will give us end-to-end verification that this branch integrates cleanly with generated code before we merge.

[parthea]

Converting to draft as it appears there are unrelated changes to bigframes. If that's not the case, move it back to ready for review