fix: callback detection logic for IIFEs in max-nested-callbacks by DMartens · Pull Request #20979 · eslint/eslint

DMartens · 2026-06-12T15:45:36Z

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I have read the contributing guidelines.

AI acknowledgment

I did not use AI to generate this PR.
(If the above is not checked) I have reviewed the AI-generated content before submitting.

What is the purpose of this pull request? (put an "X" next to an item)

[ ] Documentation update
[] Bug fix (template)
[ ] New rule (template)
[x] Changes an existing rule (template)
[ ] Add autofix to a rule
[ ] Add a CLI option
[ ] Add something to the core
[ ] Other, please explain:

What rule do you want to change?

max-nested-callbacks

What change do you want to make (place an "X" next to just one item)?

[x] Generate more warnings
[ ] Generate fewer warnings
[ ] Implement autofix
[ ] Implement suggestions

How will the change be implemented (place an "X" next to just one item)?

[ ] A new option
[x] A new default behavior
[ ] Other

Please provide some example code that this change will affect:

new Promise(() => {});
(() => {})();

What does the rule currently do for this code?
Ignores the callback passed to the constructor and counts an IIFE.

What will the rule do after it's changed?
Count the callback to the constructor and ignore IIFEs.

What changes did you make? (Give an overview)

Improve the callback detection of max-nested-callbacks:

Does not count IIFEs as a callback ((() => {})())
Counts functions passed to a constructor call as a callback (new Promise(() => {}))

Is there anything you'd like reviewers to focus on?

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mdjermanovic · 2026-06-14T09:52:48Z

Ignores the callback passed to the constructor and counts an IIFE.

I agree the IIFE case is a bug, but I don't think functions passed to constructors are usually considered callbacks.

DMartens · 2026-06-15T21:38:38Z

I included constructor calls as they are basically a special kind of function call.
While they rarely take functions as an argument, the DOM observers do (MDN documents the parameter as a "callback").

mdjermanovic · 2026-06-17T09:30:11Z

I included constructor calls as they are basically a special kind of function call.

Indeed they can be considered a special kind of function calls, but since this rule is about preferences, users could argue that the new behavior is not what they were expecting, so I think including constructor calls by default would be a breaking change for this rule rather than a bug fix, and I'm not sure if we want to add an option since this rule is frozen.

mdjermanovic · 2026-06-17T10:53:17Z

Actually, this rule isn't frozen, so we could discuss adding an option, separately from the IIFE bug fix.

DMartens · 2026-06-18T21:07:40Z

I updated the PR accordingly and added a valid test case for a callback passed to a constructor call and create an issue for including constructor calls.

mdjermanovic

LGTM, thanks!

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DMartens requested a review from a team as a code owner June 12, 2026 15:45

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DMartens added 2 commits June 18, 2026 23:01

feat: fix callback detection logic in max-nested-callbacks

cb7060f

fix: do not check callbacks of constructor calls

2198a1d

DMartens force-pushed the max-nested-callbacks-callback-detection branch from 4852491 to 2198a1d Compare June 18, 2026 21:06

chore: formatting

cf54a87

mdjermanovic approved these changes Jun 19, 2026

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mdjermanovic changed the title ~~feat: fix callback detection logic in max-nested-callbacks~~ fix: callback detection logic for IIFEs in max-nested-callbacks Jun 19, 2026

eslint-github-bot Bot added the bug ESLint is working incorrectly label Jun 19, 2026

mdjermanovic added accepted There is consensus among the team that this change meets the criteria for inclusion and removed feature This change adds a new feature to ESLint labels Jun 19, 2026

mdjermanovic moved this from Triaging to Implementing in Triage Jun 19, 2026

mdjermanovic merged commit 7feaff0 into eslint:main Jun 19, 2026
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