Missed true dependencies

[OfekShilon]

Bug Description

I'm trying to use depcheck on compiler-explorer. I get:

Unused dependencies
* buffer
* eslint-plugin-header
* events
* pug
* ts-node
Unused devDependencies
* @babel/preset-typescript
* @types/chai-as-promised
* @types/tar-fs
* @types/webpack-env
* cheerio
* css-loader
* eslint-formatter-github
* eslint-import-resolver-typescript
* file-loader
* lint-staged
* sass
* sass-loader
* sinon
* source-map-loader
* supervisor
* ts-loader

but many of these seem to be real dependencies. Specifically:

1. The compiler-explorer TypeScript source contains:

import {Buffer} from 'buffer';
...
import EventEmitter from 'events';
...
import * as cheerio from 'cheerio';

2. The js file parsed_pug_file.js contains:

const pug = require('pug');

3. The file webpack.config.esm.ts contains 'sass-loader', 'source-map-loader', 'css-loader' and 'ts-loader'
4. Makefile includes 'supervisor' (this might be outside your scope, I get it)
5. pre-commit includes 'lint-staged' (ditto)
6. .eslint-license-header.yml includes 'eslint-plugin-header'

etc. I stopped there.

Code snippets

For a complete repro with context:

$ clone --depth=1 https://github.com/compiler-explorer/compiler-explorer
$ cd compiler-explorer
$ npm install # or `make`
$ depcheck .

I'll be happy to help collect more info or debug, if that would be helpful.

Versions

• node -v: v18.17.1
• npm -v: 10.2.0
• depcheck --version: 1.4.7

[OfekShilon]

Regarding the first two, buffer and events: they fail to be count as used despite being part of an import directive because they're classified as core modules. They are, but here (and in many other projects) they're used in the front end - and so must be installed in package.json and are not unused.

Perhaps there's a way to refine the 'core module' criterion?

[znarf]

The parsed-pug folder is ignored because it contains a package.json.

See: https://github.com/depcheck/depcheck/blob/main/src/check.js#L232