#prefer-optional-chain

#Configuration

import { defineConfig, ts } from '@rslint/core';

export default defineConfig([
  ts.configs.recommended,
  {
    rules: {
      '@typescript-eslint/prefer-optional-chain': 'error',
    },
  },
]);

#Rule Details

Enforce using concise optional chain expressions instead of chained logical ANDs, negated logical ORs, or empty object coalescing patterns.

TypeScript 3.7 introduced optional chaining (?.) which provides a more concise and readable way to access deeply nested properties that may be null or undefined.

Examples of incorrect code for this rule:

foo && foo.bar;
foo && foo.bar && foo.bar.baz;
foo && foo.bar();
foo != null && foo.bar;
foo !== undefined && foo.bar;
typeof foo !== 'undefined' && foo.bar;
!foo || !foo.bar;
(foo || {}).bar;
(foo ?? {}).bar;

Examples of correct code for this rule:

foo?.bar;
foo?.bar?.baz;
foo?.bar();
foo?.bar;
foo?.bar;
foo?.bar;
!foo?.bar;
foo?.bar;
foo?.bar;

#Options

#allowPotentiallyUnsafeFixesThatModifyTheReturnTypeIKnowWhatImDoing

Type: boolean, default: false

When set to true, the rule will provide auto-fixes even when the fix may change the return type of the expression. By default, such cases are reported as suggestions only.

#checkAny

Type: boolean, default: true

When set to true, the rule will check operands typed as any when inspecting boolean expressions.

#checkUnknown

Type: boolean, default: true

When set to true, the rule will check operands typed as unknown when inspecting boolean expressions.

#checkString

Type: boolean, default: true

When set to true, the rule will check operands typed as string when inspecting boolean expressions.

#checkNumber

Type: boolean, default: true

When set to true, the rule will check operands typed as number when inspecting boolean expressions.

#checkBoolean

Type: boolean, default: true

When set to true, the rule will check operands typed as boolean when inspecting boolean expressions.

#checkBigInt

Type: boolean, default: true

When set to true, the rule will check operands typed as bigint when inspecting boolean expressions.

#requireNullish

Type: boolean, default: false

When set to true, the rule will only report on expressions where at least one operand has a type that includes null or undefined. This prevents false positives when the expression uses truthy checks for non-nullable types like string or number.

#Original Documentation

• typescript-eslint prefer-optional-chain