Yarn on dependency conflicts

alice.package.json

{
  "name": "alice",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "underscore": "1.7.x"
  }
}

bob.package.json

{
  "name": "bob",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "underscore": "1.7.x"
  }
}

foo.package.json

{
  "name": "foo",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "underscore": "1.5.x"
  }
}

main.package.json

{
  "dependencies": {
    "alice": "file:../alice",
    "bob": "file:../bob",
    "foo": "file:../foo"
  }
}

npm.txt

~/Dev/s/main » npm i                                                                                                                                   otakustay@Gray-MacBook-Pro
/Users/otakustay/Dev/s/main
├─┬ alice@1.0.0
│ └── underscore@1.7.0
├── bob@1.0.0
└─┬ foo@1.0.0
  └── underscore@1.5.2

npm WARN main No description
npm WARN main No repository field.
npm WARN main No license field.
------------------------------------------------------------
~/Dev/s/main » tree -L 3 node_modules                                                                                                                  otakustay@Gray-MacBook-Pro
node_modules
├── alice
│   └── package.json
├── bob
│   └── package.json
├── foo
│   ├── node_modules
│   │   └── underscore
│   └── package.json
└── underscore
    ├── LICENSE
    ├── README.md
    ├── package.json
    ├── underscore-min.js
    └── underscore.js

6 directories, 8 files

yarn.txt

~/Dev/s/main » yarn install                                                                                                                            otakustay@Gray-MacBook-Pro
yarn install v0.15.1
warning No license field
[1/4] 🔍  Resolving packages...
[2/4] 🚚  Fetching packages...
[3/4] 🔗  Linking dependencies...
[4/4] 📃  Building fresh packages...
success Saved lockfile.
✨  Done in 0.20s.
------------------------------------------------------------
~/Dev/s/main » ls node_modules/                                                                                                                        otakustay@Gray-MacBook-Pro
------------------------------------------------------------
~/Dev/s/main » tree -L 3 node_modules                                                                                                                  otakustay@Gray-MacBook-Pro
node_modules
├── alice
│   ├── node_modules
│   │   └── underscore
│   └── package.json
├── bob
│   ├── node_modules
│   │   └── underscore
│   └── package.json
├── foo
│   ├── node_modules
│   │   └── underscore
│   └── package.json
└── underscore
    ├── LICENSE
    ├── README.md
    ├── package.json
    ├── underscore-min.js
    └── underscore.js

10 directories, 8 files