NPM doesn't install module dependencies

This is my package.json for the module that I'm including in the parent project:

{
  "version": "0.0.1",
  "name": "module-name",
  "dependencies": {
    "express": "3.3.4",
    "grunt": "0.4.1",
    "grunt-contrib-compass": "0.4.0",
    "grunt-contrib-copy": "0.4.1",
    "grunt-contrib-cssmin": "0.4.1",
    "grunt-contrib-jshint": "0.6.3",
    "grunt-contrib-requirejs": "0.4.1",
    "grunt-contrib-uglify": "0.2.2",
    "grunt-contrib-watch": "0.5.1",
    "grunt-express-server": "0.4.1",
    "grunt-karma": "0.4.5",
    "grunt-regex-replace": "0.2.5",
    "request": "2.25.0"
  },
  "scripts": {
    "postinstall": "grunt install"
  }
}

One thing to note is that this module is contained in a private repo and I include it in the parent package.json like: "module-name": "git+ssh://git@myserver:user/module-name.git"

Solution

It looks like you hit a bug that has existed for quite a while and doesn't have solution yet. There are several open issues for this case in the npm repository:

npm install should recursively check/install dependencies https://github.com/npm/npm/issues/1341 (closed)
local private module dependencies https://github.com/npm/npm/issues/2442 (closed)

In the first one people list several workarounds that you may try.

An alternative solution may be (a little hackish) to explicitly list the dependencies as first level dependents. This requires you to maintain the list but practically it has to be done very infrequently.