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consistent-type-imports

Enforce consistent usage of type imports.

🔧

Some problems reported by this rule are automatically fixable by the --fix ESLint command line option.

TypeScript allows specifying a type keyword on imports to indicate that the export exists only in the type system, not at runtime. This allows transpilers to drop imports without knowing the types of the dependencies.

.eslintrc.cjs
module.exports = {
  "rules": {
    "@typescript-eslint/consistent-type-imports": "warn"
  }
};

Options​

This rule accepts an options object with the following properties:

interface Options {
  prefer?: "type-imports" | "no-type-imports";
  disallowTypeAnnotations?: boolean;
  fixStyle?: "separate-type-imports" | "inline-type-imports";
}

const defaultOptions: Options = [
  {
    prefer: "type-imports",
    disallowTypeAnnotations: true,
    fixStyle: "separate-type-imports",
  },
];

prefer​

This option defines the expected import kind for type-only imports. Valid values for prefer are:

  • type-imports will enforce that you always use import type Foo from '...' except referenced by metadata of decorators. It is the default.
  • no-type-imports will enforce that you always use import Foo from '...'.

Examples of correct code with {prefer: 'type-imports'}, and incorrect code with {prefer: 'no-type-imports'}.

import type { Foo } from 'Foo';
import type Bar from 'Bar';
type T = Foo;
const x: Bar = 1;

Examples of incorrect code with {prefer: 'type-imports'}, and correct code with {prefer: 'no-type-imports'}.

import { Foo } from 'Foo';
import Bar from 'Bar';
type T = Foo;
const x: Bar = 1;

fixStyle​

This option defines the expected type modifier to be added when an import is detected as used only in the type position. Valid values for fixStyle are:

  • separate-type-imports will add the type keyword after the import keyword import type { A } from '...'. It is the default.
  • inline-type-imports will inline the type keyword import { type A } from '...' and is only available in TypeScript 4.5 and onwards. See documentation here.
import { Foo } from 'Foo';
import Bar from 'Bar';
type T = Foo;
const x: Bar = 1;

disallowTypeAnnotations​

If true, type imports in type annotations (import()) are not allowed. Default is true.

Examples of incorrect code with {disallowTypeAnnotations: true}:

type T = import('Foo').Foo;
const x: import('Bar') = 1;

Usage with emitDecoratorMetadata​

The emitDecoratorMetadata compiler option changes the code the TypeScript emits. In short - it causes TypeScript to create references to value imports when they are used in a type-only location. If you are using emitDecoratorMetadata then our tooling will require additional information in order for the rule to work correctly.

If you are using type-aware linting, then you just need to ensure that the tsconfig.json you've configured for parserOptions.project has emitDecoratorMetadata turned on. Otherwise you can explicitly tell our tooling to analyze your code as if the compiler option was turned on by setting parserOptions.emitDecoratorMetadata to true.

When Not To Use It​

  • If you specifically want to use both import kinds for stylistic reasons, you can disable this rule.

Resources​