peerDepdencies of a used package not considered

Bug Description

A package that’s only in peerDependencies of a used package is still marked as unused even though it really is used.

Code snippets

Where the dependency is used:

const jsdomGlobal = require('jsdom-global');

Where the dependency is listed in package.json:

{
  "name": "test_depcheck",
  "license": "PUBLIC DOMAIN",
  "dependencies": {
    "jsdom": "~11.11.0",
    "jsdom-global": "~3.0.2"
  }
}

Versions

• node -v: v10.15.2
• npm -v: 6.4.1
• depcheck --version: 0.7.2

Extra info

If you remove jsdom from package.json, then yarn install gives the following error and the code doesn’t work:

yarn install v1.13.0
warning package.json: License should be a valid SPDX license expression
warning test_depcheck: License should be a valid SPDX license expression
[1/4] 🔍  Resolving packages...
[2/4] 🚚  Fetching packages...
[3/4] 🔗  Linking dependencies...
warning " > jsdom-global@3.0.2" has unmet peer dependency "jsdom@>=10.0.0".
[4/4] 🔨  Building fresh packages...

success Saved lockfile.
✨  Done in 0.70s.

json output:

{"dependencies":[],"devDependencies":[],"missing":{},"using":{"jsdom-global":["/Users/dlj/temp/index.js"],"jsdom":["/Users/dlj/temp/index.js"]},"invalidFiles":{},"invalidDirs":{}}

[rumpl]

@robross0606 could you open a new issue and provide a repository reproducing this error please?

[robross0606]

This still appears to be a problem. My project has a peer dependency on prom-client:

npm WARN prometheus-gc-stats@0.5.1 requires a peer of prom-client@>= 10 < 12 but none is installed. You must install peer dependencies yourself.

However, depcheck lists it as unused after installation:

C:\Code\code>depcheck --version
1.4.0

C:\Code\code>depcheck
Unused dependencies
* prom-client