fix(adapter): improve error propagation in Express-style handler

[ReneWerner87]

No description provided.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: d187018f-186c-4a19-80b6-7a82dc56289c

📥 Commits

Reviewing files that changed from the base of the PR and between e0cac19 and 12acb9e.

📒 Files selected for processing (1)

• adapter_test.go

✅ Files skipped from review due to trivial changes (1)

• adapter_test.go

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Walkthrough

The Express-style three-parameter handler adapter (func(Req, Res, func() error) error) now captures the result of c.Next() into a local nextErr and returns the handler's error if non-nil; otherwise it returns nextErr. Two tests were added to verify both precedence and propagation behavior.

Changes

Express Handler Error Propagation

Layer / File(s)	Summary
Core Logic adapter.go	In the Express-style (Req, Res, func() error) adapter, the provided next callback assigns c.Next() to a local nextErr and returns it. The adapter returns the handler's error immediately if non-nil; if the handler returns nil, the adapter returns nextErr.
Tests adapter_test.go	Added two tests: one asserting the handler's returned error is preferred over a next() error (while still invoking next()), and one asserting a next() error is propagated when the handler returns nil.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• 🔥 feat: Add support for Express.js style req/res handlers #3809: Touches the same Express-style three-parameter adapter behavior and related tests.
• 🔥 feat: Support Express-style next callback handlers #4029: Modifies adaptExpressHandler error propagation and precedence between handler return and next() errors.

Suggested reviewers

• sixcolors
• efectn

Poem

🐰 I hopped through middleware, careful and spry,
I caught the next() whisper before it could fly,
If the handler shouts, I hand that reply,
Else I pass along what next lets slip by. 🥕

🚥 Pre-merge checks | ✅ 3 | ❌ 2

❌ Failed checks (2 warnings)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The pull request description is completely missing. The repository requires a detailed description covering changes, type of change, and a comprehensive checklist.	Add a complete pull request description following the template, including details of the changes, type of change classification, and completion of the required checklist items.
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically describes the main change: improving error propagation in Express-style handler, which matches the code changes in adapter.go.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/adapter-case5-next-error-propagation

Warning

There were issues while running some tools. Please review the errors and either fix the tool's configuration or disable the tool if it's a critical failure.

🔧 golangci-lint (2.11.4)

level=error msg="[linters_context] typechecking error: pattern ./...: directory prefix . does not contain main module or its selected dependencies"

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[Copilot]

Pull request overview

This PR fixes error propagation for Express-style handlers adapted through toFiberHandler, ensuring Fiber returns the handler's own error when both the handler and next() fail. It keeps adapter behavior consistent with the other Express-style adapter variants.

Changes:

• Update the func(Req, Res, func() error) error adapter path to capture next() errors separately and only return them when the handler itself returns nil.
• Add regression tests covering handler-error precedence over next() errors.
• Add regression tests covering propagation of next() errors when the handler returns nil.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
adapter.go	Adjusts Express-style adapter error propagation for the error-returning next variant.
adapter_test.go	Adds tests validating handler-vs-next error precedence and next error propagation.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.25%. Comparing base (3e610ae) to head (12acb9e).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4250      +/-   ##
==========================================
+ Coverage   91.20%   91.25%   +0.05%     
==========================================
  Files         127      127              
  Lines       12551    12556       +5     
==========================================
+ Hits        11447    11458      +11     
+ Misses        692      687       -5     
+ Partials      412      411       -1     

Flag	Coverage Δ
unittests	91.25% <100.00%> (+0.05%)	⬆️

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[gemini-code-assist]

Code Review

This pull request modifies the adaptExpressHandler function in adapter.go to correctly handle error propagation for Express-style handlers. It ensures that errors from the next callback are returned if the handler itself returns nil, while prioritizing errors returned by the handler if both occur. Two new test cases have been added to adapter_test.go to validate these scenarios. I have no feedback to provide.