fix(core): Account for readonly properties when replacing circular references

[ivov]

Summary

With runners enabled, a Code node that tries to log an object with a readonly property errors out, because of the assignment when replacing circular references when serializing for the RPC call. This can be reproduced with this Code node script:

const testObj = {};
Object.defineProperty(testObj, 'toString', {
 value: function() { return '[readonly]'; },
 writable: false,
 enumerable: true,
 configurable: false
});

console.log(testObj);

return [];

⚠️ Note on testing: Spent a reasonable amount of time trying to write a Vitest test case that reproduces this scenario, but all my attempts either always pass (before and after fix) or always fail (before and after fix). Let me know if you find a way to test this. Else let's move forward as this is a rare case.

Related Linear tickets, Github issues, and Community forum posts

#18328

Review / Merge checklist

• PR title and summary are descriptive. (conventions)
• Docs updated or follow-up ticket created.
• Tests included.
• PR Labeled with release/backport (if the PR is an urgent fix that needs to be backported)

[cubic-dev-ai]

cubic analysis

No issues found across 1 file. Review in cubic

[codecov]

Codecov Report

❌ Patch coverage is 28.57143% with 10 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
packages/workflow/src/utils.ts	28.57%	10 Missing ⚠️

📢 Thoughts on this report? Let us know!

[tomi]

🚀

[currents-bot]

✅

E2E Tests: n8n tests passed after 4m 20.1s

🟢 519 · 🔴 0 · ⚪️ 0

View Run Details

Run Details

• Project: n8n

• Groups: 3

• Framework: Playwright

• Run Status: Passed

• Commit: 615015f

• Spec files: 108

• Overall tests: 519

• Duration: 4m 20.1s

• Parallelization: 3

Groups

GroupId	Results	Spec Files Progress
ui	🟢 44 · 🔴 0 · ⚪️ 0	14 / 14
ui:isolated	🟢 6 · 🔴 0 · ⚪️ 0	2 / 2
No name	🟢 469 · 🔴 0 · ⚪️ 0	92 / 92

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[janober]

Got released with n8n@1.108.0