steal-tools/lib/stream/filter_bundle_graph.js

var through = require("through2");
var omit = require("lodash/omit");
var keys = require("lodash/keys");
var assign = require("lodash/assign");
var multimatch = require("multimatch");

module.exports = function() {
	return through.obj(function(data, enc, done) {
		try {
			done(null, filterGraph(data));
		} catch (err) {
			done(err);
		}
	});
};

function getGlobPattern(data) {
	var options = data.options;

	return options.filter || "**";
}

function filterGraph(data) {
	var visited = {};
	var filtered = {};
	var graph = data.graph;
	var baseUrl = data.loader.baseURL;

	keys(graph).forEach(function visit(name) {
		// don't visit a node twice
		if (visited[name]) return;

		visited[name] = true;
		var node = graph[name];

		if (node) {
			var address = node.load.address;
			var pattern = getGlobPattern(data);
			var relative = address.replace(baseUrl, "");

			if (multimatch(relative, pattern).length) {
				node.dependencies.forEach(visit);
				filtered[name] = node;
			}
		}
	});

	return assign({}, omit(data, "graph"), { graph: filtered });
}