@lint-suite/eslint-plugin-no-inline-object-types

An ESLint rule for TypeScript that keeps object type literals in named type aliases. It prevents inline object types in parameters, properties, generic arguments, and other nested positions while allowing a type alias's direct object body.

Compatibility

Requires ESLint ^10.9.1 and TypeScript >=6.0.3. The package is built and tested with Node.js 24.

Installation

pnpm add -D @lint-suite/eslint-plugin-no-inline-object-types eslint@^10.9.1 typescript@^6.0.3 typescript-eslint@^8.69.0

Configuration

The plugin does not configure a parser. This flat config parses the TypeScript examples below:

import plugin from '@lint-suite/eslint-plugin-no-inline-object-types';
import tseslint from 'typescript-eslint';

export default [
  {
    files: ['**/*.ts'],
    languageOptions: { parser: tseslint.parser },
    plugins: { 'no-inline-object-types': plugin },
    rules: { 'no-inline-object-types/no-inline-object-types': 'error' }
  }
];

Options

This rule has no options.

Scope and exemptions

The only exempt object type literal is the direct right-hand side of a type alias. The rule still reports object type literals nested in a type alias's union, intersection, property, array element, or generic argument. Interfaces are not exempt: their inline member object types are reported.

Examples

Each snippet below is checked by this rule alone, not by an entire ESLint configuration.

Valid examples

1. Direct type-alias object body

type User = { readonly name: string };

2. Generic type-alias object body

type Result<T> = { readonly value: T };

3. Alias that references a named type

type Session = User;

4. Array type alias

type Users = User[];

5. Mapped type alias

type Flags = { [Key in 'open' | 'closed']: boolean };

Invalid examples

1. Nested property object type

type Order = { customer: { name: string } };

Extract { name: string } into its own named alias.

2. Object array element type

type Order = { lines: { sku: string }[] };

Name the array element object type.

3. Union member object type

type Result = { value: { id: string } | null };

Name the object member before using it in the union.

4. Intersection object types

type Model = { id: string } & { updatedAt: Date };

Both object literals are nested in the intersection and are reported.

5. Function parameter object type

function save(input: { title: string }): void {}

Declare a named input type instead.

6. Generic object argument

type State = Readonly<{ open: boolean }>;

Declare the object shape as a named type before passing it to Readonly.