import-js/eslint-plugin-import

[BUG] `no-unused-modules` doesn't support the export-default-from syntax

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#1938 opened on Nov 8, 2020

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bughelp wanted

Description

When using the version 2.22.1, the syntax described in the ECMAScript Proposal export default from doesn't seem to be supported by the rule no-unused-modules:

// index.js
export Component from './Component';

$ eslint .
Oops! Something went wrong! :(

ESLint: 7.12.1

TypeError: Cannot read property 'name' of undefined
Occurred while linting /Users/me/project/src/components/index.js:2
    at /Users/me/project/node_modules/eslint-plugin-import/lib/rules/no-unused-modules.js:675:46
    at Array.forEach (<anonymous>)
    at /Users/me/project/node_modules/eslint-plugin-import/lib/rules/no-unused-modules.js:671:32
    at Array.forEach (<anonymous>)
    at updateImportUsage (/Users/me/project/node_modules/eslint-plugin-import/lib/rules/no-unused-modules.js:664:17)
    at Program:exit (/Users/me/project/node_modules/eslint-plugin-import/lib/rules/no-unused-modules.js:895:9)
    at /Users/me/project/node_modules/babel-eslint/node_modules/eslint/lib/linter/safe-emitter.js:45:58
    at Array.forEach (<anonymous>)
    at Object.emit (/Users/me/project/node_modules/babel-eslint/node_modules/eslint/lib/linter/safe-emitter.js:45:38)
    at NodeEventGenerator.applySelector (/Users/me/project/node_modules/babel-eslint/node_modules/eslint/lib/linter/node-event-generator.js:254:26)

As a workaround, we could use this syntax to achieve the same goal:

// index.js
export { default as Component } from './Component';

Contributor guide

Tech stack
javascriptnodejs
Domain
toolingdeveloper experience
Issue type
bug
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
JavaScriptESLint plugin structureAST
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
75
Research direction
Focus on the file `lib/rules/no unused modules.js`, specifically the `updateImportUsage` function around lines 664-675. The error occurs because the code expects a `source` property on an export declaration, but the `export default from` syntax produces a different AST structure. Investigate the AST node for `export default from` (likely an `ExportNamedDeclaration` with a different `source` shape) and update the logic to handle it, possibly by checking for the new syntax or using a different property to get the exported name.