What rule do you want to change?

no-nested-ternary

What change do you want to make?

Generate more warnings

How do you think the change should be implemented?

A new default behavior

Example code

/* eslint no-nested-ternary: "error" */

// JavaScript code with nested ternary operators

const thing = foo ? bar : baz === qux ? quxx : foobar;
foo ? (baz === qux ? quxx() : foobar()) : bar();

// TypeScript code with nested ternary operators

type KindOf<T> = T extends string
  ? 'string'
  : T extends number
    ? 'number'
    : T extends boolean
      ? 'boolean'
      : T extends any[]
        ? 'array'
        : 'other';

What does the rule currently do for this code?

The no-nested-ternary rule currently doesn’t understand TypeScript syntax, so it fails to flag errors when nested conditional types are used.

That’s because the TypeScript AST differs slightly from the JavaScript AST for ternary operations.

TypeScript AST

What will the rule do after it's changed?

For the reasons mentioned above, I’d like to request adding TypeScript syntax support to the no-nested-ternary rule.

Participation

• I am willing to submit a pull request to implement this change.

Additional comments

This issue is follow-up to #19173