[VertexAI] Add Swift 6 testing to CI

[paulb777]

• Add Swift 6 testing to CI
• Update unit tests to build in Swift
• Add Changelog note
• Workaround remaining warning(s) see below
• A first pass at fixing the warning is in [Vertex AI] Refactor generateContentStream to fix Swift 6 warning #14504

[gemini-code-assist]

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[andrewheard]

/gemini review

[gemini-code-assist]

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[paulb777]

/gemini review

[gemini-code-assist]

Code Review

This pull request adds Swift 6 testing to the CI, updates unit tests, and adds a changelog note. The changes are well-structured and address the intended purpose. However, there are a few minor suggestions that could improve the code quality and maintainability.

Summary of Findings

• TODO comment in workflow file: The workflow file contains a TODO comment indicating a remaining warning in GenerativeAIService. It's important to address this warning and remove the --allow-warnings flag to ensure code quality and prevent potential issues from being overlooked.
• Swift version update in podspec: The pull request includes a step to set the Swift version in the FirebaseVertexAI.podspec file. While this is necessary for Swift 6 testing, it's important to ensure that the change is correctly implemented and doesn't introduce any unintended side effects.
• @preconcurrency import: The @preconcurrency import in VertexComponentTests.swift seems like a workaround. It would be good to understand why this is needed and whether there's a better way to address the underlying issue.

Assessment

The pull request introduces Swift 6 testing to the CI and updates unit tests to build in Swift. The changes look good overall, but there are a few minor suggestions for improvement. Please address the comments before merging, and ensure that another reviewer approves this code as well.

[paulb777]

Gemini:

• TODO work is underway in [Vertex AI] Refactor generateContentStream to fix Swift 6 warning #14504
• The podspec version cannot be updated until we drop Xcode 15 support
• The @preconcurrency workaround is not a priority in the unit tests.

[gemini-code-assist]

Thanks for the update, @paulb777. It's helpful to know the context behind the TODOs and other decisions in this PR. This information clarifies the reasoning behind the current state of the code and helps to avoid unnecessary back-and-forth.