fix: prevent infinite growth of links in relations

[MinCrohn]

No description provided.

[gemini-code-assist]

Summary of Changes

Hello @MinCrohn, 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 resolves an issue where the graphical representation of relations could continuously grow due to an additive update mechanism. The change ensures that the Relations component's update method now explicitly replaces all existing relation data with the new input, preventing an infinite accumulation of links and maintaining a clean, accurate display of relationships.

Highlights

• Prevent Infinite Link Growth: The core change introduces a mergeStrategy: 'replace' option to the update method within the Relations class. This is crucial for preventing an unintended accumulation or 'infinite growth' of links when relations data is updated.
• Data Update Strategy: By explicitly setting the merge strategy to 'replace', the system now ensures that existing relations data is completely overwritten with new changes, rather than being merged additively. This guarantees that the displayed relations accurately reflect the latest state without duplication.

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[gemini-code-assist]

Code Review

This pull request aims to fix an issue where the links array in Relations elements grows indefinitely with each update. The proposed solution is to enforce a 'replace' merge strategy for all updates on Relations elements. While this correctly changes the behavior for the links array, it unfortunately introduces a critical side effect, breaking partial style updates. Additionally, the tests that verify the links update behavior have not been updated to reflect the change, and will fail. My review includes a detailed comment on the problematic code with suggestions for a more robust solution.

[gemini-code-assist]

While this change to use mergeStrategy: 'replace' correctly fixes the issue of the links array growing on each update, it introduces two significant problems:

1. Broken Style Updates: This change causes a side effect where partial style updates no longer work. The _applyRelationstyle handler also uses mergeStrategy. With 'replace', it will replace the entire style on the underlying graphics object, instead of merging. For instance, updating just the width of a link will cause its color to be reset. This is a critical bug.

2. Failing Tests: This change alters the behavior of links updates from merging to replacement. However, the existing tests in src/tests/render/Relations.test.js and src/tests/undo-redo/Relations.test.js still expect the old merging behavior (e.g., expect(updatedLinks.length).toBe(2)). These tests will now fail and need to be updated to reflect the new intended behavior.

A more targeted fix is needed. One approach is to refactor _applyRelationstyle to not depend on mergeStrategy. Alternatively, you could explore ways to apply the replace strategy only to the links array without affecting other properties during the update process.

Please address the style update bug and update the relevant tests.