[manzoorwanijk]

With auto-install-peers=false, npm stops adding a package only to satisfy a dependency's required peer, and instead reports every package that depends on a package with a required peer without declaring that peer itself.
Reports are EPEERUNDECLARED warnings; under strict-peer-deps, violations by the root or a workspace fail the install unless --force is set.

• Placement skips such peers in #problemEdges and #loadPeerSet, and prunes ones already locked (build-ideal-tree.js).
• The rule reads manifests, so all install strategies report the same result (peer-declarations.js).
• npm ci rejects a lockfile that still contains auto-installed peers.
• Third-party violations can be fixed with packageExtensions or .npm-extension.
• An optional peer of the root does not install a required peer, and a present optional peer counts as a declaration.
• A dependent that declares a peer it does not install passes that peer's own peers to its consumer, so any declaration of them counts.

References

Implements npm/rfcs#926