Ignore "Local NPM module not found" warning in Grunt - gruntjs

Question

I'm using matchdep to read dependencies from my package.json file into grunt.
require('matchdep').filterAll('grunt-*').forEach(grunt.loadNpmTasks);
I have my dependencies split between dependencies (for everyone) and devDependencies (for front-end developers.)
Our back-end devs will run the following to get a build of the static assets without requiring jasmine, phantomJS, etc (things that will be run by front-end devs and the CI server)
$ npm install --production
$ grunt build
However, when using the --production build, grunt.loadNpmTasks() will emit a warning for any missing packages.
>> Local Npm module "grunt-contrib-watch" not found. Is it installed?
Is there a way to supress this warning?

Answer 1

You have to question why your "back-end devs" would have to actually build your package - put otherwise, why do they need grunt but NOT devDependencies. This is kind of backwards (requiring users to build your package is certainly an anti-pattern).
That being said, using matchdep, you can / should use:
require('matchdep').filter inside your "production" target
require('matchdep').filterAll inside your "development" target
Certainly, that would require you to specialize your grunt build (eg: have grunt builddev and grunt buildproduction - or maybe use environment variables) - but again, see above...

Answer 2

You can use CLI flags to pass options into grunt. For consistency, I am using a --production flag, just as I do with npm.
So, from the CLI:
$ grunt build --production
And then in the Gruntfile:
var dependencies;
// test for the production flag
if (grunt.option('production')) {
// scan dependencies but ignore dev
dependencies = require('matchdep').filter('grunt-*');
} else {
// scan all dependencies
dependencies = require('matchdep').filterAll('grunt-*');
}
// load only relevant dependencies
dependencies.forEach(grunt.loadNpmTasks);
This is done at the top of the module before any custom tasks are registered.