[AI] Update empty parts check for urlContextMetadata

[paulb777]

Follow on to #15262 now that urlContext tool support has been added

Summary of Changes

This pull request refines the isEmpty logic within the Candidate struct of the Firebase AI SDK. It specifically updates the isEmpty computed property to account for urlContextMetadata, preventing Candidate objects from being incorrectly identified as empty when they contain relevant URL context information. This change ensures more accurate content generation responses and is accompanied by new unit tests to validate the updated behavior.

Highlights

• Candidate.isEmpty logic update: The isEmpty computed property in the Candidate struct has been updated to include urlContextMetadata in its evaluation, ensuring that candidates with this metadata are no longer considered empty.
• Test coverage for Candidate.isEmpty: New unit tests have been added to verify the correctness of the Candidate.isEmpty property, specifically covering scenarios where urlContextMetadata is present or absent.
• @testable import for testing: The test file GenerateContentResponseTests.swift now uses @testable import FirebaseAI to allow access to internal types for comprehensive testing.

Changelog

• FirebaseAI/Sources/GenerateContentResponse.swift
  • Modified the isEmpty computed property in the Candidate struct to include urlContextMetadata in its check.
• FirebaseAI/Tests/Unit/Types/GenerateContentResponseTests.swift
  • Added @testable import FirebaseAI to enable testing of internal types.
  • Introduced new test cases (testCandidateIsEmpty_allEmpty_isTrue and testCandidateIsEmpty_withURLContextMetadata_isFalse) to thoroughly validate the updated Candidate.isEmpty logic.

Activity

• gemini-code-assist[bot] provided information regarding its usage.
• google-oss-bot issued a warning about a missing changelog entry.
• paulb777 requested a review from Gemini Code Assist.
• gemini-code-assist[bot] provided a review comment suggesting the use of try XCTUnwrap for robust URL handling in tests.
• paulb777 requested a summary from Gemini Code Assist.

[gemini-code-assist]

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[google-oss-bot]

	1 Warning
⚠️	Did you forget to add a changelog entry? (Add #no-changelog to the PR description to silence this warning.)

Generated by 🚫 Danger

[paulb777]

/gemini review

[gemini-code-assist]

Code Review

This pull request correctly updates the Candidate.isEmpty check to also consider urlContextMetadata. The logic is sound, and the change is accompanied by new unit tests that validate the updated behavior. The code quality is good. I have one minor suggestion to improve the robustness of the new test case.

[paulb777]

/gemini summary