import.meta.resolve doesn't provide a file extension while require.resolve does.

[hmidmrii]

Node.js Version

v20.14.0

NPM Version

v10.7.0

Operating System

Windows 11

Subsystem

Other

Description

I have an ESM file that have the following import statement:

import keyBy from 'lodash-es/keyBy';

which is throwing an error about not being able to find the file:

Error [ERR_MODULE_NOT_FOUND]: Cannot find module '\node_modules\lodash-es\keyBy' imported from file.mjs
Did you mean to import "lodash-es/keyBy.js"?

same code in CJS env was working (obviously using lodash instead of lodash-es),

after investigating I tried resolving instead of importing to check, and here's the result:

// CJS
require.resolve('lodash');
// "node_modules/lodash/index.js"

require.resolve('lodash/keyBy');
// "node_modules/lodash/keyBy.js"

// ------------------------------

// ESM
import.meta.resolve('lodash-es');
// "node_modules/lodash-es/lodash.js"

import.meta.resolve('lodash-es/keyBy');
// "node_modules/lodash-es/keyBy"

as you can see only lodash-es/keyBy doesn't have a file extension 🤕

is this an expected behavior or did I catch a big fish (jk)?

please correct me I'm missing something here 🙏

Minimal Reproduction

import keyBy from 'lodash-es/keyBy';

Output

Error [ERR_MODULE_NOT_FOUND]: Cannot find module '\node_modules\lodash-es\keyBy' imported from file.mjs
Did you mean to import "lodash-es/keyBy.js"?

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[hmidmrii]

it's not urgent at all, since I can use import { keyBy } from 'lodash-es'; and it will work perfectly fine,

but it would be good to learn the behaviors of import

[ljharb]

That's because require uses the CJS algorithm, which automatically fills in file extensions for you - ESM does not.

Neither lodash nor lodash-es provide an exports field, so you are required to use the full path, including extension, for import.