sort-type-union-intersection-members

Enforce members of a type union/intersection to be sorted alphabetically.

Sorting union (|) and intersection (&) types can help:

• keep your codebase standardized
• find repeated types
• reduce diff churn

Attributes

• Included in configs
  • ✅ Recommended
  • 🔒 Strict
• Fixable
  • 🔧 Automated Fixer
  • 💡 Suggestion Fixer
• 💭 Requires type information

Rule Details

Sorting within each group is done using the following code:

const collator = new Intl.Collator('en', {
  sensitivity: 'base',
  numeric: true,
});

function compare(a, b) {
  return collator.compare(a, b) || (a < b ? -1 : a > b ? 1 : 0);
}

In other words, the types are sorted alphabetically, case-insensitively and treating numbers like a human would, falling back to character code sorting in case of ties.

Examples of code for this rule:

❌ Incorrect

type T1 = B | A;

type T2 = { b: string } & { a: string };

type T3 = [1, 2, 4] & [1, 2, 3];

type T4 =
  | [1, 2, 4]
  | [1, 2, 3]
  | { b: string }
  | { a: string }
  | (() => void)
  | (() => string)
  | 'b'
  | 'a'
  | 'b'
  | 'a'
  | readonly string[]
  | readonly number[]
  | string[]
  | number[]
  | B
  | A
  | string
  | any;

✅ Correct

type T1 = A | B;

type T2 = { a: string } & { b: string };

type T3 = [1, 2, 3] & [1, 2, 4];

type T4 =
  | any
  | string
  | A
  | B
  | number[]
  | string[]
  | readonly number[]
  | readonly string[]
  | 'a'
  | 'b'
  | 'a'
  | 'b'
  | (() => string)
  | (() => void)
  | { a: string }
  | { b: string }
  | [1, 2, 3]
  | [1, 2, 4];

.eslintrc.cjs

module.exports = {
  "rules": {
    "@typescript-eslint/sort-type-union-intersection-members": "warn"
  }
};

Options

This rule accepts an options object with the following properties:

interface Options {
  /**
   * Whether to check intersection types.
   */
  checkIntersections?: boolean;
  /**
   * Whether to check union types.
   */
  checkUnions?: boolean;
  /**
   * Ordering of the groups.
   */
  groupOrder?: (
    | "conditional"
    | "function"
    | "import"
    | "intersection"
    | "keyword"
    | "nullish"
    | "literal"
    | "named"
    | "object"
    | "operator"
    | "tuple"
    | "union"
  )[];
}

const defaultOptions: Options = [
  {
    checkIntersections: true,
    checkUnions: true,
    groupOrder: [
      "named",
      "keyword",
      "operator",
      "literal",
      "function",
      "import",
      "conditional",
      "object",
      "tuple",
      "intersection",
      "union",
      "nullish",
    ],
  },
];

groupOrder

Each member of the type is placed into a group, and then the rule sorts alphabetically within each group. The ordering of groups is determined by this option.

• conditional - Conditional types (A extends B ? C : D)
• function - Function and constructor types (() => void, new () => type)
• import - Import types (import('path'))
• intersection - Intersection types (A & B)
• keyword - Keyword types (any, string, etc)
• literal - Literal types (1, 'b', true, etc)
• named - Named types (A, A['prop'], B[], Array<C>)
• object - Object types ({ a: string }, { [key: string]: number })
• operator - Operator types (keyof A, typeof B, readonly C[])
• tuple - Tuple types ([A, B, C])
• union - Union types (A | B)
• nullish - null and undefined

Resources

• Rule source
• Test source