import/extensions

import "./user" and import "./user.js" can name the same file. Browsers and Node.js only accept the second in ES modules, while bundlers and Bun accept both. This rule keeps a project on one style, for all files or per extension.

It checks import, export ... from, import() and require(). Built-in modules and bare package names such as "react" or "@babel/core" are never checked.

Configure#

Off by default. To turn it on:

bunfig.toml

[lint.rules]
"import/extensions" = "error" # or "warn"

Every option, set to its default:

bunfig.toml

[lint.rules]
"import/extensions" = [
  "error",
  "never", # "always", "ignorePackages", "never" or object
  {
    pattern = {},
    ignorePackages = false,
    checkTypeImports = false,
    pathGroupOverrides = [], # list of objects
  },
]

Examples#

Reported:

export function createUser(name) {
  return { name };
}

import { createUser } from "./user";

Not reported:

export function createUser(name) {
  return { name };
}

import { createUser } from "./user.js";
import { join } from "node:path";
import { useState } from "react";

Options#

bunfig.toml

[lint.rules]
"import/extensions" = ["error", "never", { json = "always" }]

The first option sets the style for every extension:

Option	What it does
`"never"` (default)	Report an extension that the path doesn't need, such as `./user.js` where `./user` finds the same file.
`"always"`	Report a path without an extension.
`"ignorePackages"`	Like `"always"`, but paths into packages such as `"lodash/fp/map"` aren't checked.

export function createUser(name) {
  return { name };
}

import { createUser } from "./user.js";

import map from "lodash/fp/map";

import map from "lodash/fp/map";

An object after it, or instead of it, holds exceptions and more settings:

Option	Default	What it does
an extension, such as `js` or `json`	the first option	`"always"` or `"never"` for files with that extension.
`pattern`	`{}`	The same extension entries, in their own object. If you set `ignorePackages` or `checkTypeImports`, put the entries in here. Entries written next to those two options are ignored.
`ignorePackages`	`false`	Don't require an extension in paths into packages.
`checkTypeImports`	`false`	Also require extensions in `import type` and `export type`.
`pathGroupOverrides`	`[]`	A list of `{ pattern, action }`. A path that matches the glob `pattern` is skipped if `action` is `"ignore"`. With `"enforce"` it's checked even if it looks like a package. It's ignored unless you also set `pattern`, `ignorePackages` or `checkTypeImports`.

import { createUser } from "./user";
import settings from "./settings.json";

import type { User } from "./user";

import type { User } from "./user";

import { routes } from "~/generated/routes";

import { routes } from "~/generated/routes";

The rule looks up which file ./user stands for, the way Bun and TypeScript do, so it knows that it's ./user.ts:

export function createUser(name: string) {
  return { name };
}

import { createUser } from "./user.ts";

export function createUser(name: string) {
  return { name };
}

import { createUser } from "./user";

With an ESLint config it only tries .mjs, .js, .json and .node, like Node.js does, unless settings["import/resolver"] says otherwise.