feat(core): add partUtils module with unit tests

[kamja44]

Refactors part-related helper functions into a new partUtils.ts module and adds comprehensive unit tests.

Extracted partToString and getResponseText from summarizer.ts into packages/core/src/utils/partUtils.ts. This improves code organization and reusability.

Added a new test file partUtils.test.ts with thorough unit tests for both functions, covering various cases including invalid inputs and edge cases.

Renamed the module from partHelpers.ts to partUtils.ts to align with the project's naming conventions.

TLDR
This PR extracts partToString and getResponseText into a new partUtils.ts module and adds dedicated unit tests for these utility functions. This improves code organization, reusability, and test coverage.

Dive Deeper
Previously, partToString and getResponseText were co-located within summarizer.ts. While functional, this placement was not ideal for reusability and clear separation of concerns. This PR moves these general-purpose utility functions into their own dedicated module, partUtils.ts, under packages/core/src/utils/.

Furthermore, comprehensive unit tests have been added in partUtils.test.ts to ensure the correctness and robustness of these functions. The tests cover various scenarios, including:

Handling null and undefined inputs for partToString.

Correctly concatenating string and object parts.

Extracting text from GenerateContentResponse objects, including cases with no candidates, no content, or mixed part types.

Adherence to the project's Array linting rule for array types in the test mock.

The module was initially named partHelpers.ts but was renamed to partUtils.ts to maintain consistency with existing utility file naming conventions within the project.

Testing Matrix

	🍏	🪟	🐧
npm run	❓	❓	✅
npx	❓	❓	✅
Docker	❓	❓	✅
Podman	❓	-	-
Seatbelt	❓	-	-

Linked issues / bugs

• Closes Refactor: Extract Part Utilities and Add Unit Tests #4583

[gemini-code-assist]

Summary of Changes

Hello @kamja44, 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 improves the codebase's organization and testability by refactoring common utility functions related to content parts into their own module. This move not only enhances code reusability but also ensures the reliability of these critical functionalities through the addition of dedicated and thorough unit tests.

Highlights

• Code Organization & Refactoring: I've extracted the partToString and getResponseText helper functions from summarizer.ts into a new, dedicated module: packages/core/src/utils/partUtils.ts. This improves separation of concerns and enhances reusability of these core utility functions.
• Improved Test Coverage: Comprehensive unit tests have been added for both partToString and getResponseText in a new file, packages/core/src/utils/partUtils.test.ts. These tests cover various scenarios, including invalid inputs, edge cases, and different content part types, ensuring the robustness of these utilities.
• Naming Convention Alignment: The new utility module was initially named partHelpers.ts but was renamed to partUtils.ts to maintain consistency with existing naming conventions within the project.

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[gemini-code-assist]

Code Review

This pull request effectively refactors part-related utility functions into a new partUtils.ts module, accompanied by a solid set of unit tests. This is a great improvement for code organization and reusability.

My main feedback is on the implementation of getResponseText, where I've identified a correctness issue related to how text parts are filtered and a behavioral inconsistency in its return values. I've provided a suggestion to make the function more robust and predictable.

Overall, this is a valuable change, and with the suggested fix, it will be even better.

[jacob314]

there is a somewhat similar helper method in
geminiRequest.ts

gemini-cli/packages/core/src/core/geminiRequest.ts

Line 16 in 9bdcdf9

export function partListUnionToString(value: PartListUnion): string {

Would it be feasible to unify these two similar util methods?
Ideally geminiRequest.ts could just call the partToString method from partsUtil.ts

[gemini-code-assist]

That's an excellent observation, @jacob314! Unifying similar utility methods across the codebase, especially by leveraging the newly introduced partToString in partUtils.ts, would indeed further enhance code reusability and maintainability.

@kamja44, this is a valuable suggestion for a follow-up improvement. If it's a straightforward change, you might consider incorporating it into this PR, or creating a separate issue to track this refactoring in geminiRequest.ts.

[kamja44]

Hi @jacob314 ,

Thank you for your valuable feedback and for suggesting the unification of the partToString and partListUnionToString methods. I've implemented the changes accordingly, and I believe this results in a cleaner and more robust solution.

Here's a summary of the changes:

1. Unified partToString Function:
   The partToString function in packages/core/src/utils/partUtils.ts has been enhanced to support both pure text extraction and detailed summary generation. It now accepts an optional options parameter with a verbose flag:

   • When verbose: true is passed, the function returns human-readable summary strings (e.g., [Video Metadata], [Function Call: myFunction]), integrating the behavior previously found in partListUnionToString.
   • When verbose is false or omitted, it preserves the original behavior of extracting only the plain text.

2. geminiRequest.ts Wrapper:
   The partListUnionToString function in packages/core/src/core/geminiRequest.ts now acts as a thin wrapper that simply delegates to partToString(value, { verbose: true }), preserving existing behavior and API compatibility.

3. Consolidated Tests:
   All unit tests related to part string conversion have been consolidated into partUtils.test.ts, covering both default and verbose modes. The redundant geminiRequest.test.ts file has been removed.

This approach centralizes the logic, improves reusability, and maintains compatibility with existing interfaces—all while aligning with project conventions.

Please let me know if you have any questions or further suggestions.

Thanks again!

[jacob314]

Good idea adding a verbose option to enable supporting this as a refactor that didn't change any logic!