[derive] Improve hygiene testing

[joshlf]

In zerocopy-derive tests, import zerocopy as zerocopy_renamed so
that references to ::zerocopy fail to resolve. This ensures that no
generated code hard-codes zerocopy or ::zerocopy, and instead all
references make use of the provided custom crate name.

---

• 　 [WIP][derive] Factor out unsafe impl block building #2893
• 👉 [derive] Improve hygiene testing #2898

Latest Update: v13 — Compare vs v12

📚 Full Patch History

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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 enhances the hygiene testing within the zerocopy-derive crate. The core purpose is to guarantee that the procedural macros generate code that is resilient to crate renaming, ensuring that all references to the zerocopy crate are dynamic and configurable. This is achieved through systematic renaming of the crate in test environments and updating the macro's internal mechanisms to respect these renames, thereby preventing unintended dependencies on specific crate names.

Highlights

• Improved Hygiene Testing: The zerocopy-derive crate now includes more robust hygiene testing to ensure that generated procedural macro code correctly references the zerocopy crate, even when it's renamed.
• Crate Renaming in Tests: All relevant test files have been updated to import zerocopy as zerocopy_renamed and explicitly use #[zerocopy(crate = "zerocopy_renamed")] in derived types. This setup ensures that any hard-coded references to ::zerocopy or zerocopy in generated code will cause compilation failures, thus validating macro hygiene.
• Dynamic Crate Path Resolution: The internal logic of the derive macros has been modified to use a dynamic zerocopy_crate variable, passed via a context object, for all trait implementations. This prevents hard-coding the crate name and allows for flexible renaming.
• Absolute Path Enforcement for Custom Crate Names: The parsing of the #[zerocopy(crate = "...")] attribute in src/util.rs has been enhanced to ensure that the provided custom crate name is always treated as an absolute path (prefixed with ::), improving consistency and preventing potential resolution issues.

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[gemini-code-assist]

Code Review

This pull request improves hygiene testing for the derive macros by renaming the zerocopy dev-dependency to zerocopy_renamed. This forces all generated code to respect the #[zerocopy(crate = "...")] attribute instead of using hardcoded paths. The changes are extensive but systematic, covering the derive logic itself and all test cases. The implementation appears correct and robust. I have no specific comments on the code changes.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.90%. Comparing base (f905feb) to head (75c1680).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2898   +/-   ##
=======================================
  Coverage   91.90%   91.90%           
=======================================
  Files          20       20           
  Lines        5877     5877           
=======================================
  Hits         5401     5401           
  Misses        476      476           

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