webpack/lib/optimize/AggressiveMergingPlugin.js

Packs CommonJs/AMD modules for the browser. Allows to split your codebase into multiple bundles, which can be loaded on demand. Support loaders to preprocess files, i.e. json, jade, coffee, css, less, ... and your custom stuff.

/*
	MIT License http://www.opensource.org/licenses/mit-license.php
	Author Tobias Koppers @sokra
*/
function AggressiveMergingPlugin(options) {
	this.options = options || {};
}
module.exports = AggressiveMergingPlugin;

AggressiveMergingPlugin.prototype.apply = function(compiler) {
	var options = this.options;
	var minSizeReduce = options.minSizeReduce || 1.5;
	function getParentsWeight(chunk) {
		return chunk.parents.map(function(p) {
			return p.initial ? options.entryChunkMultiplicator || 10 : 1;
		}).reduce(function(a, b) {
			return a + b;
		}, 0);
	}
	compiler.plugin("compilation", function(compilation) {
		compilation.plugin("optimize-chunks", function(chunks) {
			var combinations = [];
			chunks.forEach(function(a, idx) {
				if(a.initial) return;
				for(var i = 0; i < idx; i++) {
					var b = chunks[i];
					if(b.initial) continue;
					combinations.push([b, a]);
				}
			});

			combinations.forEach(function(pair) {
				var a = pair[0].size({chunkOverhead: 0});
				var b = pair[1].size({chunkOverhead: 0});
				var ab = pair[0].integratedSize(pair[1], {chunkOverhead: 0});
				pair.push({ a: a, b: b, ab: ab });
				if(ab === false) {
					pair.unshift(false);
				} else if(options.moveToParents) {
					var aOnly = ab - b;
					var bOnly = ab - a;
					var common = a + b - ab;
					var newSize = common + getParentsWeight(pair[0]) * aOnly + getParentsWeight(pair[1]) * bOnly;
					pair.push({ aOnly: aOnly, bOnly: bOnly, common: common, newSize: newSize });
				} else {
					var newSize = ab;
				}

				pair.unshift((a + b) / newSize);
			});
			combinations = combinations.filter(function(pair) {
				return pair[0] !== false;
			});
			combinations.sort(function(a,b) {
				return b[0] - a[0];
			});

			var pair = combinations[0];

			if(!pair) return;
			if(pair[0] < minSizeReduce) return;

			if(options.moveToParents) {
				var commonModules = pair[1].modules.filter(function(m) {
					return pair[2].modules.indexOf(m) >= 0;
				});
				var aOnlyModules = pair[1].modules.filter(function(m) {
					return commonModules.indexOf(m) < 0;
				});
				var bOnlyModules = pair[2].modules.filter(function(m) {
					return commonModules.indexOf(m) < 0;
				});
				aOnlyModules.forEach(function(m) {
					pair[1].removeModule(m);
					m.removeChunk(pair[1]);
					pair[1].parents.forEach(function(c) {
						c.addModule(m);
						m.addChunk(c);
					});
				});
				bOnlyModules.forEach(function(m) {
					pair[2].removeModule(m);
					m.removeChunk(pair[2]);
					pair[2].parents.forEach(function(c) {
						c.addModule(m);
						m.addChunk(c);
					});
				});
			}
			if(pair[1].integrate(pair[2], "aggressive-merge")) {
				chunks.splice(chunks.indexOf(pair[2]), 1);
				this.restartApplyPlugins();
			}
		});
	});
};