About

A Phantom Dependency is dependency used in a project:

• that is resolved (found)
• but is not declared as dependency in the project itself.

Example

If your project uses a dependency A that depends on B. The code of B is available.

If your project uses B without declaring it, B is a phantom dependency.

Technically, you shouldn't be able to use B without adding it to your project dependency but dependency manager may have a dependency resolution mechanism that allows it.

For instance:

• node require default function will search in all parent/sub directory
• the node manager puts all dependency under the same directory (node_modules)