fix(async-retryer): preserve non-Error message and cause in normalized errors

[theBGuy]

🎯 Changes

• Fix AsyncRetryer error normalization for non-Error throws.
• Preserve readable message when a plain object with a string message field is thrown.
• Attach the original thrown value as Error.cause.
• Add regression coverage to ensure:
  • message is preserved as "readable error"
  • cause equals the original thrown object

✅ Checklist

• I have followed the steps in the Contributing guide.
• I have tested this code locally with pnpm run test:pr.

🚀 Release Impact

• This change affects published code, and I have generated a changeset.
• This change is docs/CI/dev-only (no release).

Summary by CodeRabbit

• Bug Fixes
  • Improved error handling during retry operations by better normalizing non-Error thrown values. Error messages from plain objects are now properly preserved, and the original thrown value is accessible via the error cause property. This enables superior error tracking and debugging capabilities.

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR fixes error normalization in AsyncRetryer.execute(). When a retried function rejects with a non-Error value, it is now converted to an Error whose message is derived from the thrown value's message property or string representation, and the original value is attached as the error's cause for later inspection.

Changes

AsyncRetryer Error Normalization

Layer / File(s)	Summary
Error normalization implementation and validation packages/pacer/src/async-retryer.ts, packages/pacer/tests/async-retryer.test.ts	When handling exceptions in execute, non-Error throws are converted into Error objects with messages derived from a value's message field (if available) or String(error), and the original thrown value is attached as cause. A test validates that plain-object rejections are normalized and the original object is preserved.
Patch release documentation .changeset/big-bikes-wash.md	Changeset entry documents the @tanstack/pacer patch bump and describes the AsyncRetryer error-normalization behavior change.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

A retryer once threw and caught plain object messiness,
Now errors wrap gently, preserving the cause with faithfulness,
Where message flows clear and the cause keeps truth,
A patch brings precision to async pursuits. 🐰✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the primary change: fixing AsyncRetryer error normalization to preserve non-Error message and cause.
Description check	✅ Passed	The PR description follows the template with all required sections completed. Changes are clearly documented, checklist items are checked, release impact is noted, and a changeset was generated.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
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 unit tests (beta)

• Create PR with unit tests

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[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

This PR improves AsyncRetryer error normalization so that when a non-Error value (e.g., a plain object) is thrown, the normalized Error preserves a readable message and retains the original thrown value via cause.

Changes:

• Normalize non-Error thrown values by extracting a message field when present and attaching the original value as Error.cause.
• Add a regression test ensuring plain-object error message and cause are preserved.
• Add a changeset to publish the fix as a patch.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
packages/pacer/src/async-retryer.ts	Updates error normalization to preserve plain-object messages and attach the original thrown value as cause.
packages/pacer/tests/async-retryer.test.ts	Adds a test covering thrown plain objects and verifying message/cause behavior.
.changeset/big-bikes-wash.md	Documents the patch release for the error-normalization fix.

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[coderabbitai]

🧹 Nitpick comments (1)

packages/pacer/tests/async-retryer.test.ts (1)

391-407: 💤 Low value

Consider adding test coverage for additional edge cases.

The current test validates the main use case (plain object with string message), and existing tests cover string, null, and undefined. For completeness, you might consider adding tests for:

• Plain object without a message property (should fall back to String(error))
• Plain object with non-string message property (e.g., { message: 123 })

These would ensure the fallback logic is thoroughly validated.

🤖 Prompt for 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.

In `@packages/pacer/tests/async-retryer.test.ts` around lines 391 - 407, Add two
new tests in packages/pacer/tests/async-retryer.test.ts next to the existing
"should preserve plain object error message and cause" test to cover edge cases:
(1) a plain object error without a message property (e.g., { code: 'E002' }) and
assert that AsyncRetryer.execute() produces an Error whose message falls back to
String(error) and whose cause is the original object; (2) a plain object with a
non-string message (e.g., { message: 123 }) and assert that execute() converts
that message to a string for Error.message and sets cause to the original
object; reference the AsyncRetryer class and its execute() method when locating
where to add these tests.

🤖 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.

Nitpick comments:
In `@packages/pacer/tests/async-retryer.test.ts`:
- Around line 391-407: Add two new tests in
packages/pacer/tests/async-retryer.test.ts next to the existing "should preserve
plain object error message and cause" test to cover edge cases: (1) a plain
object error without a message property (e.g., { code: 'E002' }) and assert that
AsyncRetryer.execute() produces an Error whose message falls back to
String(error) and whose cause is the original object; (2) a plain object with a
non-string message (e.g., { message: 123 }) and assert that execute() converts
that message to a string for Error.message and sets cause to the original
object; reference the AsyncRetryer class and its execute() method when locating
where to add these tests.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 60b245f8-b810-48ce-aed3-227146820f8a

📥 Commits

Reviewing files that changed from the base of the PR and between a894009 and 4a83cc6.

📒 Files selected for processing (3)

• .changeset/big-bikes-wash.md
• packages/pacer/src/async-retryer.ts
• packages/pacer/tests/async-retryer.test.ts