fix(middleware): guard typed-nil *fiber.Error matched by errors.As by fredcamaral · Pull Request #48 · LerianStudio/lib-observability

fredcamaral · 2026-08-10T20:39:05Z

What

errors.As matches a typed-nil *fiber.Error inside a joined chain (errors.Join((*fiber.Error)(nil), ...)) and leaves the target nil. Reading .Code then panics with a nil-pointer dereference, inside WithHTTPErrorHandling, the middleware whose purpose is closing exactly this defect class. Found by a downstream consumption review in Matcher (one of the six rows of its own typed-nil test table), confirmed by execution against the released version.

Because errors.As stops at the first type match, a bare nil guard was not enough: a typed-nil *fiber.Error joined before a valid fiber.NewError(400, ...) would shadow it and downgrade the mapped status to a generic 500. The fix is a shared extractor that mirrors errors.As traversal but skips nil matches and keeps searching, used both in the substitution branch of WithHTTPErrorHandling and in httpStatusCode:

func asFiberError(err error) *fiber.Error {
	if err == nil {
		return nil
	}
	if fiberErr, ok := err.(*fiber.Error); ok && fiberErr != nil {
		return fiberErr
	}
	// ... As(any) bool, then Unwrap() error / Unwrap() []error,
	// depth-first in join order, skipping nil matches ...
}

Regression tests cover joined/delegating typed-nil shapes against Fiber's default ErrorHandler, including a typed-nil *fiber.Error preceding a valid one (flat and nested in an earlier subtree).

Affects both released lines: this PR fixes v3; the identical fix for the v2.1.x maintenance line is pushed on fix/typed-nil-fiber-error-substitution-v2 (cut from the v2.1.2 tag, needs a v2.1.3 tag on that branch, since main is now the /v3 module path).

errors.As matches a typed-nil *fiber.Error inside a joined chain (errors.Join((*fiber.Error)(nil), ...)) and leaves the target nil; reading .Code then panics with a nil-pointer dereference - inside the finalizer whose purpose is closing exactly this defect class. Confirmed by execution on the released line. Same fix shipped for the v2 maintenance line on fix/typed-nil-fiber-error-substitution-v2. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_019J6AsXF9EbWtJ7CV7WtSdD

coderabbitai · 2026-08-10T20:39:28Z

No actionable comments were generated in the recent review. 🎉

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middleware/error_handling.go

📝 Walkthrough

Walkthrough

The middleware now traverses wrapped and joined errors safely. Typed-nil *fiber.Error values no longer cause panics or mask later valid Fiber errors. Regression tests cover HTTP handling and status extraction.

Changes

HTTP error handling

Layer / File(s)	Summary
Fiber error traversal and integrations `middleware/error_handling.go`, `middleware/logging.go`	`asFiberError` traverses direct, custom, wrapped, and joined errors. HTTP error handling and logging use it to ignore typed-nil matches and preserve valid mapped errors.
Unsafe error-chain regression coverage `middleware/error_handling_regression_test.go`	Tests cover typed-nil errors, nil-cause wrappers, nested joined chains, panic-free handling, internal-server-error fallback, and valid later Fiber errors.

Possibly related PRs

LerianStudio/lib-observability#45: Both changes modify HTTP error normalization and Fiber error-chain handling.
LerianStudio/lib-observability#46: Both changes update typed-nil-safe handling in the same middleware files.
LerianStudio/lib-observability#47: Both changes update chained Fiber error handling in the same middleware files.

✨ Finishing Touches

✨ Simplify code

Create PR with simplified code
Commit simplified code in branch fix/typed-nil-fiber-error-substitution

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lerian-studio · 2026-08-10T20:40:27Z

⚠️ Invalid Source Branch

Pull requests to main can only come from:

develop
release-candidate
hotfix/*

Your source branch: fix/typed-nil-fiber-error-substitution

Please change the base branch or create a PR from an allowed branch.

lerian-studio · 2026-08-10T20:40:57Z

🔍 PR Validation Summary

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Check	Status	Blocking
Source Branch	✅ success	yes
PR Title	✅ success	yes
PR Description	✅ success	yes
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Auto Labels	✅ success	no
PR Metadata	✅ success	no

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lerian-studio · 2026-08-10T20:41:24Z

🔒 Security Scan Results — `lib-observability`

✅ PR Mergeable — no blocking findings

Stage	Status	Blocking?
Filesystem Scan	✅ Clean	—
Docker Image Scan	➖ Skipped	—
Docker Hub Health Score	➖ Skipped	—
Pre-release Version Check	✅ Clean	—

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✅ No unstable version pins found.

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coderabbitai

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@middleware/error_handling.go`:
- Around line 100-108: The error handling must skip typed-nil *fiber.Error
values and continue searching for a later valid Fiber error. Add a shared
extractor that traverses joined and wrapped error trees, returns only non-nil
*fiber.Error values, and reuse it in this normalization branch and
httpStatusCode; add regression coverage for a typed-nil Fiber error preceding a
valid one.

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Create a new PR with the fixes

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Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: 810ed5b2-1c98-4ee6-8bdd-e796e598e488

📥 Commits

Reviewing files that changed from the base of the PR and between f540cf0 and a1aba12.

📒 Files selected for processing (2)

middleware/error_handling.go
middleware/error_handling_regression_test.go

lerian-studio · 2026-08-10T20:43:47Z

📊 Unit Test Coverage Report: `lib-observability`

Metric	Value
Overall Coverage	`87.6%` ✅ PASS
Threshold	`80%`

Coverage by Package

Package	Coverage
`github.com/LerianStudio/lib-observability/v3/assert`	98.2%
`github.com/LerianStudio/lib-observability/v3/constants`	83.3%
`github.com/LerianStudio/lib-observability/v3/grpcmiddleware`	78.7%
`github.com/LerianStudio/lib-observability/v3/httpobs`	77.8%
`github.com/LerianStudio/lib-observability/v3/log`	90.7%
`github.com/LerianStudio/lib-observability/v3/messagingobs`	89.4%
`github.com/LerianStudio/lib-observability/v3/metrics`	91.4%
`github.com/LerianStudio/lib-observability/v3/middleware`	84.1%
`github.com/LerianStudio/lib-observability/v3/redaction`	95.8%
`github.com/LerianStudio/lib-observability/v3/redisobs`	63.1%
`github.com/LerianStudio/lib-observability/v3/runtime`	80.9%
`github.com/LerianStudio/lib-observability/v3/sqlobs`	64.2%
`github.com/LerianStudio/lib-observability/v3/telemetrycore`	84.2%
`github.com/LerianStudio/lib-observability/v3/tracing`	88.0%
`github.com/LerianStudio/lib-observability/v3/zap`	96.1%
`github.com/LerianStudio/lib-observability/v3`	91.5%

Generated by Go PR Analysis workflow

… joined chains X-Lerian-Ref: 0x1 Co-authored-by: Codesmith <codesmith-bot@users.noreply.github.com>

coderabbitai

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@middleware/error_handling.go`:
- Around line 134-145: Update asFiberError to resolve the reported errorlint and
inamedparam violations while preserving its manual traversal and typed-nil
handling. Rename the parameter in the local As interface to satisfy inamedparam,
and add narrow linter suppressions for the intentional direct type assertions
and inspection in the fiber.Error checks. Run golangci-lint run ./... and
confirm no configured violations remain.

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Fix all unresolved CodeRabbit comments on this PR:

Push a commit to this branch (recommended)
Create a new PR with the fixes

ℹ️ Review info

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Run ID: e747f629-e48f-4e23-833e-c85bd63ae3db

📥 Commits

Reviewing files that changed from the base of the PR and between a1aba12 and 7103562.

📒 Files selected for processing (3)

middleware/error_handling.go
middleware/error_handling_regression_test.go
middleware/logging.go

X-Lerian-Ref: 0x1 Co-authored-by: Codesmith <codesmith-bot@users.noreply.github.com>

fredcamaral changed the base branch from main to develop August 10, 2026 20:41

coderabbitai Bot requested changes Aug 10, 2026

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Comment thread middleware/error_handling.go Outdated

lerian-studio assigned fredcamaral Aug 10, 2026

lerian-studio added size/S PR changes 50–199 lines middleware HTTP/gRPC observability middleware tests Unit, integration and end-to-end tests labels Aug 10, 2026

fix(middleware): skip typed-nil *fiber.Error shadowing a valid one in…

7103562

… joined chains X-Lerian-Ref: 0x1 Co-authored-by: Codesmith <codesmith-bot@users.noreply.github.com>

lerian-studio added size/M PR changes 200–499 lines and removed size/S PR changes 50–199 lines labels Aug 10, 2026

coderabbitai Bot requested changes Aug 10, 2026

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Comment thread middleware/error_handling.go Outdated

fix(middleware): satisfy errorlint and inamedparam in asFiberError

7cefe45

X-Lerian-Ref: 0x1 Co-authored-by: Codesmith <codesmith-bot@users.noreply.github.com>

coderabbitai Bot approved these changes Aug 10, 2026

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fredcamaral merged commit f61444c into develop Aug 10, 2026
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github-actions Bot deleted the fix/typed-nil-fiber-error-substitution branch August 10, 2026 21:02

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fix(middleware): guard typed-nil *fiber.Error matched by errors.As - #48

fix(middleware): guard typed-nil *fiber.Error matched by errors.As#48
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