What is the difference between unmet and incorrect peer dependency?

Question

I believe I understand what "unmet peer dependency" means. For example "package-a" depends on "package-b@^2.1.5" but no version of [email protected] (>=2.1.5) is installed.

But "incorrect dependency" baffles me. It would make no sense to say "package-a is asking for an incorrect dependency". Is it saying that the dependency listed in package-lock.json or yarn.lock doesn't match what package-a says it needs? If this is correct, then how would this be resolved?

When I search for specific discussion about "incorrect dependency" on Github, it seems to show up on issues in the yarn or npm repos. And the resolution usually seems to be a fix to yarn or npm. Is this message for bugs in yarn/npm?

If I search https://docs.npmjs.com/ for "incorrect peer dependency", I get no results.

Answer 1

• Unmet peer dependency means the dependency has not been installed at all.
• Incorrect peer dependency means it has been installed, but in the wrong version.

Given these package.json

{
  name: "app"
  dependencies: {
    "package-a": "*"
  }
}

{
  name: "package-a",
  peerDependencies: {
    "package-b": "^2.1.5"
  }
}

A yarn install will give you an unmet peer dependency, since app does not make sure package-b gets installed.

If you add it as a dependency, but in a wrong version

{
  name: "app"
  dependencies: {
    "package-a": "*",
    "package-b": "~2.0.0"
  }
}

you will get an incorrect peer dependency.