[derive] Automatically bless output test output

[joshlf]

Closes #2903

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• 👉 [derive] Automatically bless output test output #2905

Latest Update: v5 — Compare vs v4

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[gemini-code-assist]

Summary of Changes

Hello @joshlf, 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 developer experience for maintaining zerocopy-derive tests by implementing an automated 'blessing' system. This system allows developers to easily regenerate and update the expected output of derive macros, eliminating the need for manual updates and reducing the chance of errors when macro expansions change. The change centralizes the update process for various test outputs into a single, more descriptive script.

Highlights

• Automated Test Output Blessing: Introduced a new mechanism to automatically 'bless' (update) the expected output files for zerocopy-derive tests. This is similar to how trybuild handles UI tests, simplifying the process of updating expected macro expansion output.
• Script Renaming and Expansion: The tools/update-ui-test-files.sh script has been renamed to tools/update-expected-test-output.sh and its functionality expanded to include the blessing of zerocopy-derive output tests in addition to UI tests.
• Documentation Update: The agent_docs/ui_tests.md documentation has been updated to reflect the new script name and its broader scope, now covering both UI and derive output tests.
• Code Formatting Consistency: Several .expected.rs files in zerocopy-derive/src/output_tests/expected/ received minor whitespace and formatting adjustments, likely as a result of the new pretty-printing logic applied during the blessing process.

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[gemini-code-assist]

Code Review

This pull request introduces a valuable enhancement to the testing workflow by adding a "blessing" mechanism for derive macro output tests. The changes are well-implemented, using an environment variable (ZEROCOPY_BLESS) to toggle between test execution and updating expected output files. The use of prettyplease to normalize both actual and expected outputs is a great practice that makes the tests more robust and less brittle to formatting changes. The related documentation and scripts have been updated accordingly. Overall, this is a solid improvement that will enhance developer productivity and test maintainability.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.90%. Comparing base (05ae8da) to head (49e1b08).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2905   +/-   ##
=======================================
  Coverage   91.90%   91.90%           
=======================================
  Files          20       20           
  Lines        5877     5877           
=======================================
  Hits         5401     5401           
  Misses        476      476           

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