no-useless-rename.md

Disallow renaming import, export, and destructured assignments to the same name (no-useless-rename)

ES2015 allows for the renaming of references in import and export statements as well as destructuring assignments. This gives programmers a concise syntax for performing these operations while renaming these references:

import { foo as bar } from "baz";
export { foo as bar };
let { foo: bar } = baz;

With this syntax, it is possible to rename a reference to the same name. This is a completely redundant operation, as this is the same as not renaming at all. For example, this:

import { foo as foo } from "bar";
export { foo as foo };
let { foo: foo } = bar;

is the same as:

import { foo } from "bar";
export { foo };
let { foo } = bar;

Rule Details

This rule disallows the renaming of import, export, and destructured assignments to the same name.

Options

This rule allows for more fine-grained control with the following options:

• ignoreImport: When set to true, this rule does not check imports
• ignoreExport: When set to true, this rule does not check exports
• ignoreDestructuring: When set to true, this rule does not check destructuring assignments

By default, all options are set to false:

"no-useless-rename": ["error", {
    "ignoreDestructuring": false,
    "ignoreImport": false,
    "ignoreExport": false
}]

Examples of incorrect code for this rule by default:

/*eslint no-useless-rename: "error"*/

import { foo as foo } from "bar";
import { "foo" as foo } from "bar";
export { foo as foo };
export { foo as "foo" };
export { foo as foo } from "bar";
export { "foo" as "foo" } from "bar";
let { foo: foo } = bar;
let { 'foo': foo } = bar;
function foo({ bar: bar }) {}
({ foo: foo }) => {}

Examples of correct code for this rule by default:

/*eslint no-useless-rename: "error"*/

import * as foo from "foo";
import { foo } from "bar";
import { foo as bar } from "baz";
import { "foo" as bar } from "baz";

export { foo };
export { foo as bar };
export { foo as "bar" };
export { foo as bar } from "foo";
export { "foo" as "bar" } from "foo";

let { foo } = bar;
let { foo: bar } = baz;
let { [foo]: foo } = bar;

function foo({ bar }) {}
function foo({ bar: baz }) {}

({ foo }) => {}
({ foo: bar }) => {}

Examples of correct code for this rule with { ignoreImport: true }:

/*eslint no-useless-rename: ["error", { ignoreImport: true }]*/

import { foo as foo } from "bar";

Examples of correct code for this rule with { ignoreExport: true }:

/*eslint no-useless-rename: ["error", { ignoreExport: true }]*/

export { foo as foo };
export { foo as foo } from "bar";

Examples of correct code for this rule with { ignoreDestructuring: true }:

/*eslint no-useless-rename: ["error", { ignoreDestructuring: true }]*/

let { foo: foo } = bar;
function foo({ bar: bar }) {}
({ foo: foo }) => {}

When Not To Use It

You can safely disable this rule if you do not care about redundantly renaming import, export, and destructuring assignments.

Related Rules

• object-shorthand which can enforce this behavior for properties in object literals.

Compatibility

• JSCS: disallowIdenticalDestructuringNames