no-duplicate-imports

Disallow duplicate module imports

Using a single import statement per module will make the code clearer because you can see everything being imported from that module on one line.

In the following example the module import on line 1 is repeated on line 3. These can be combined to make the list of imports more succinct.

import { merge } from 'module';
import something from 'another-module';
import { find } from 'module';

Rule Details

This rule requires that all imports from a single module that can be merged exist in a single import statement.

Example of incorrect code for this rule:

/*eslint no-duplicate-imports: "error"*/

import { merge } from 'module';
import something from 'another-module';
import { find } from 'module';

Example of correct code for this rule:

/*eslint no-duplicate-imports: "error"*/

import { merge, find } from 'module';
import something from 'another-module';

Example of correct code for this rule:

/*eslint no-duplicate-imports: "error"*/

// not mergeable
import { merge } from 'module';
import * as something from 'module';

Options

This rule has an object option:

• "includeExports": true (default false) checks for exports in addition to imports.
• "allowSeparateTypeImports": true (default false) allows a type import alongside a value import from the same module in TypeScript files.

includeExports

If re-exporting from an imported module, you should add the imports to the import-statement, and export that directly, not use export ... from.

Example of incorrect code for this rule with the { "includeExports": true } option:

/*eslint no-duplicate-imports: ["error", { "includeExports": true }]*/

import { merge } from 'module';

export { find } from 'module';

Example of correct code for this rule with the { "includeExports": true } option:

/*eslint no-duplicate-imports: ["error", { "includeExports": true }]*/

import { merge, find } from 'module';

export { find };

Example of correct code for this rule with the { "includeExports": true } option:

/*eslint no-duplicate-imports: ["error", { "includeExports": true }]*/

import { merge, find } from 'module';

// cannot be merged with the above import
export * as something from 'module';

// cannot be written differently
export * from 'module';

allowSeparateTypeImports

TypeScript allows importing types using import type. By default, this rule flags instances of import type that have the same specifier as import. The allowSeparateTypeImports option allows you to override this behavior.

Example of incorrect TypeScript code for this rule with the default { "allowSeparateTypeImports": false } option:

/*eslint no-duplicate-imports: ["error", { "allowSeparateTypeImports": false }]*/

import { someValue } from 'module';
import type { SomeType } from 'module';

Example of correct TypeScript code for this rule with the default { "allowSeparateTypeImports": false } option:

/*eslint no-duplicate-imports: ["error", { "allowSeparateTypeImports": false }]*/

import { someValue, type SomeType } from 'module';

Example of incorrect TypeScript code for this rule with the { "allowSeparateTypeImports": true } option:

/*eslint no-duplicate-imports: ["error", { "allowSeparateTypeImports": true }]*/

import { someValue } from 'module';
import type { SomeType } from 'module';
import type { AnotherType } from 'module';

Example of correct TypeScript code for this rule with the { "allowSeparateTypeImports": true } option:

/*eslint no-duplicate-imports: ["error", { "allowSeparateTypeImports": true }]*/

import { someValue } from 'module';
import type { SomeType, AnotherType } from 'module';

Version

This rule was introduced in ESLint v2.5.0.

Resources

• Rule source
• Tests source