import-js/eslint-plugin-import

`import/no-duplicates` and const enum-s

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#3149 opened on Jan 23, 2025

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bughelp wantedtypescript

Description

I'm using using eslint-plugin-import v2.31.0, eslint v9.18.0 and typescript v5.5.4 configuration for the plugin: import/no-duplicates is ['error', { 'prefer-inline': true }].

I have an npm package that has both type definitions (type or interfaces) and const enum-s, for example:

export const enum SomeEnum {
  Foo = 'foo',
  Bar = 'bar',
}

export interface Something {
  baz:string
}

When I am trying to import both, an interface and enum - eslint complains that it must be in one line, like this:

import { type Something, SomeEnum } from 'some-package';

but typescript can't compile such typescript file, fails with error: "Error: Module not found: Error: Can't resolve 'some-package'" there is an issue in typescript repo about this problem, but it is very old and it seems it will not be resolved in near future: https://github.com/microsoft/TypeScript/issues/40344

for now I will have to have such imports in 2 lines:

import type { Something } from 'some-package';
import { SomeEnum } from 'some-package';

and I will have to set 'prefer-inline' to false, but would be cool to be able to have those 2 lines only for the const enum-s and not for all other imports.

Contributor guide

Tech stack
javascripttypescriptnodejs
Domain
toolingdeveloper experience
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
TypeScripteslint plugin import internalsconst enum behavior
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50
Research direction
The issue requests an enhancement to the `import/no duplicates` rule when `prefer inline` is true. The rule currently forces combining type and const enum imports into one line, but TypeScript cannot compile such combined imports due to a known limitation (TypeScript#40344). To implement this, examine the rule's source code in `src/rules/no duplicates.js` (or similar) to understand how it merges imports. Look for existing logic that handles `type` imports and `prefer inline`. The fix should allow separate lines for imports that include const enums while still enforcing inlining for other imports. Consider checking if a configuration option like `allowConstEnum` or a similar mechanism is feasible. Also review comments and linked issues for prior discussion.