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Rslint

    no-unsafe-optional-chaining

    Configuration

    PresetConfigured Value
    ✅ js.configs.recommended"error"
    rslint.config.ts
    import { defineConfig, js } from '@rslint/core';

export default defineConfig([
  js.configs.recommended,
  {
    rules: {
      'no-unsafe-optional-chaining': 'error',
    },
  },
]);

    Rule Details

    Disallows using optional chaining in contexts where the undefined value is not allowed. Optional chaining (?.) can short-circuit to undefined. When the result is used in a position where undefined causes a TypeError or unexpected behavior, this rule reports it.

    Examples of incorrect code for this rule:

    (obj?.foo)(); // TypeError if obj?.foo is undefined
(obj?.foo).bar; // TypeError
new (obj?.foo)(); // TypeError
const { a } = obj?.foo; // TypeError (destructuring undefined)
[...obj?.foo]; // TypeError (spreading undefined)
for (const x of obj?.foo) {
} // TypeError (iterating undefined)
'foo' in obj?.bar; // TypeError
foo instanceof obj?.bar; // TypeError
class Foo extends obj?.bar {} // TypeError

    Examples of correct code for this rule:

    obj?.foo; // standalone is fine
obj?.foo(); // optional call is fine
(obj?.foo ?? bar)(); // fallback via ??
(obj?.foo || bar).baz; // fallback via ||
obj?.foo?.bar; // chaining is fine

    Options

    disallowArithmeticOperators

    When set to true, also reports arithmetic operations on optional chaining results, which can produce NaN. Default is false.

    Examples of incorrect code with { "disallowArithmeticOperators": true }:

    obj?.foo + bar; // may be NaN
+obj?.foo; // may be NaN
-obj?.foo; // may be NaN
obj?.foo * bar; // may be NaN

    Original Documentation