Grunt and NPM, package all production dependencies - node.js

Question

I am unsure when the way the NPM installs dependencies changed.
In the past I remember that if in my project.json I had a dependency on "abc", which in turn would depend on "xyz", a npm install would result in something like:
package.json
node_modules/
abc/
node_modules/
xyz/
some-dev-dep/
When packaging my node project to be used by AWS Lambda, I would have to include that node_modules structure (less any dev-dependencies that were there). I would use Grunt for my packaging, so I wrote this handy thing to help me get all production dependencies into this zip (extracting part of my gruntfile.js):
function getDependencies(pkg) {
return Object.keys(pkg.dependencies)
.map(function(val) { return val + '/**'; });
}
var config = {
compress: {
prod: {
options: {
archive: 'public/lambda.zip'
},
files: [
{ src: 'index.js', dest: '/' },
{ expand: true, cwd: 'node_modules/', src: getDependencies(pkg), dest: '/node_modules' }
]
}
}
};
This would work because dependencies of my dependencies were nested.
Recently (or maybe not-so-recently) this has changed (I am unsure when as I was using very old version of NPM and updated it recently).
Now if I depend on "abc" which in turn depends on "xyz" I will get:
node_modules/
abc/
xyz/
some-dev-dep/
As you can see, my way of getting only production dependencies just won't work.
Is there any easy way to get only list of production dependencies (together with sub-dependencies) within grunt job?
I could do it using recursive function scanning for my dependencies, and then checking project.json files of those and then searching for sub-dependencies etc. This approach seems like a lot of hassle that is possibly a common scenario for many projects...

Answer 1

Here is a function that returns an array of the production dependency module names. (Note: you might need to have the 'npm' module installed locally in your project for this to work.)
/**
* Returns an array of the node dependencies needed for production.
* See https://docs.npmjs.com/cli/ls for info on the 'npm ls' command.
*/
var getProdDependencies = function(callback) {
require('child_process').exec('npm ls --prod=true --parseable=true', undefined,
function(err, stdout, stderr) {
var array = stdout.split('\n');
var nodeModuleNames = [];
array.forEach(function(line) {
var index = line.indexOf('node_modules');
if (index > -1) {
nodeModuleNames.push(line.substr(index + 13));
}
});
callback(nodeModuleNames);
});
};

Answer 2

This change was introduced with the release of npm 3 (see npm v3 Dependency Resolution).
It's not exactly clear why you need to use Grunt at all. If what you want to do is get only production dependencies you can simply run:
npm install --production
With the --production flag, all dev dependencies will be ignored. The same is also true if the NODE_ENV environment variable is set to 'production'.