Webpack plugin for rails assets compatible manifest - ruby-on-rails

Question

I'm trying to fully replace the rails asset pipeline with a webpack based pipeline. I've got the dev setup with the webpack-dev-server and hot reloading etc all working beautifully. Now what I'm trying to achieve is a compilation step for production that would mimic how rails compiles assets (digesting / generating a compatible manifest.json file) such that I can still use helpers like javascript_include_tag etc. This is where I'm stuck.
I've read lots of tutorials on using webpack with rails, but they all end up writing their own view helpers to load the assets. I'm trying to avoid this because I don't want extra overhead or for devs to need to understand a different pipeline. I also want config like asset_host= to work out of the box for using a CDN etc.
Ultimately, what I want is something similar to gulp-rev-rails-manifest that generates a rails-asset-pipeline compatible manifest file on compilation, but I haven't found a plugin (yet) that exists for Webpack. So...
is it possible to run a webpack build through a gulp stream using webpack only (ie not using gulp-webpack) so I can use the above gulp plugin. The reason I don't want to use gulp-webpack is that it takes over your entries / output etc and I find that whole setup confusing since this all already exists in webpack.config
Or
Does anyone have any decent resources on writing plugins for Webpack. It seems a bit of a black box to me and the official site has a menu section for "How to write a plugin" but it's not actually a link to anything.
Or
Is there actually a plugin that will do exactly this and I don't know how to search properly on the interwebs.
Any help is greatly appreciated :)

Answer 1

Running webpack in a gulp task is very simple:
var webpack = require('webpack');
var webpackConfig = require('./webpack.config');
gulp.task('webpack', function(done) {
webpack(webpackConfig, function(err, stats) {
done(err);
});
});
Note that the stats object provided to the webpack callback contains information about all assets emitted by webpack, so you could potentially use it to generate your own manifest.
Here are a few webpack plugins you might find useful:
https://github.com/sporto/assets-webpack-plugin
https://github.com/danethurber/webpack-manifest-plugin
https://github.com/diurnalist/chunk-manifest-webpack-plugin
While there is no official tutorial on how to create a plugin, there's still a Plugin API doc that describes the different interfaces your plugins can hook into. The webpack source and github contain a lot of webpack plugin examples.
Here's a very simple plugin that just logs assets:
module.exports = function() {
this.plugin('done', function(stats) {
console.log(stats.toJson().assets);
});
};