webpack
Version:
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, jsx, es7, css, less, ... and your custom stuff.
230 lines (212 loc) • 6.11 kB
JavaScript
/*
MIT License http://www.opensource.org/licenses/mit-license.php
Author Tobias Koppers @sokra
*/
"use strict";
const NO_MARKER = 0;
const IN_PROGRESS_MARKER = 1;
const DONE_MARKER = 2;
const DONE_MAYBE_ROOT_CYCLE_MARKER = 3;
const DONE_AND_ROOT_MARKER = 4;
/**
* @template T
*/
class Node {
/**
* @param {T} item the value of the node
*/
constructor(item) {
this.item = item;
/** @type {Set<Node<T>>} */
this.dependencies = new Set();
this.marker = NO_MARKER;
/** @type {Cycle<T> | undefined} */
this.cycle = undefined;
this.incoming = 0;
}
}
/**
* @template T
*/
class Cycle {
constructor() {
/** @type {Set<Node<T>>} */
this.nodes = new Set();
}
}
/**
* @template T
* @typedef {Object} StackEntry
* @property {Node<T>} node
* @property {Node<T>[]} openEdges
*/
/**
* @template T
* @param {Iterable<T>} items list of items
* @param {function(T): Iterable<T>} getDependencies function to get dependencies of an item (items that are not in list are ignored)
* @returns {Iterable<T>} graph roots of the items
*/
module.exports = (items, getDependencies) => {
/** @type {Map<T, Node<T>>} */
const itemToNode = new Map();
for (const item of items) {
const node = new Node(item);
itemToNode.set(item, node);
}
// early exit when there is only a single item
if (itemToNode.size <= 1) return items;
// grab all the dependencies
for (const node of itemToNode.values()) {
for (const dep of getDependencies(node.item)) {
const depNode = itemToNode.get(dep);
if (depNode !== undefined) {
node.dependencies.add(depNode);
}
}
}
// Set of current root modules
// items will be removed if a new reference to it has been found
/** @type {Set<Node<T>>} */
const roots = new Set();
// Set of current cycles without references to it
// cycles will be removed if a new reference to it has been found
// that is not part of the cycle
/** @type {Set<Cycle<T>>} */
const rootCycles = new Set();
// For all non-marked nodes
for (const selectedNode of itemToNode.values()) {
if (selectedNode.marker === NO_MARKER) {
// deep-walk all referenced modules
// in a non-recursive way
// start by entering the selected node
selectedNode.marker = IN_PROGRESS_MARKER;
// keep a stack to avoid recursive walk
/** @type {StackEntry<T>[]} */
const stack = [
{
node: selectedNode,
openEdges: Array.from(selectedNode.dependencies)
}
];
// process the top item until stack is empty
while (stack.length > 0) {
const topOfStack = stack[stack.length - 1];
// Are there still edges unprocessed in the current node?
if (topOfStack.openEdges.length > 0) {
// Process one dependency
const dependency = topOfStack.openEdges.pop();
switch (dependency.marker) {
case NO_MARKER:
// dependency has not be visited yet
// mark it as in-progress and recurse
stack.push({
node: dependency,
openEdges: Array.from(dependency.dependencies)
});
dependency.marker = IN_PROGRESS_MARKER;
break;
case IN_PROGRESS_MARKER: {
// It's a in-progress cycle
let cycle = dependency.cycle;
if (!cycle) {
cycle = new Cycle();
cycle.nodes.add(dependency);
dependency.cycle = cycle;
}
// set cycle property for each node in the cycle
// if nodes are already part of a cycle
// we merge the cycles to a shared cycle
for (
let i = stack.length - 1;
stack[i].node !== dependency;
i--
) {
const node = stack[i].node;
if (node.cycle) {
if (node.cycle !== cycle) {
// merge cycles
for (const cycleNode of node.cycle.nodes) {
cycleNode.cycle = cycle;
cycle.nodes.add(cycleNode);
}
}
} else {
node.cycle = cycle;
cycle.nodes.add(node);
}
}
// don't recurse into dependencies
// these are already on the stack
break;
}
case DONE_AND_ROOT_MARKER:
// This node has be visited yet and is currently a root node
// But as this is a new reference to the node
// it's not really a root
// so we have to convert it to a normal node
dependency.marker = DONE_MARKER;
roots.delete(dependency);
break;
case DONE_MAYBE_ROOT_CYCLE_MARKER:
// This node has be visited yet and
// is maybe currently part of a completed root cycle
// we found a new reference to the cycle
// so it's not really a root cycle
// remove the cycle from the root cycles
// and convert it to a normal node
rootCycles.delete(dependency.cycle);
dependency.marker = DONE_MARKER;
break;
// DONE_MARKER: nothing to do, don't recurse into dependencies
}
} else {
// All dependencies of the current node has been visited
// we leave the node
stack.pop();
topOfStack.node.marker = DONE_MARKER;
}
}
const cycle = selectedNode.cycle;
if (cycle) {
for (const node of cycle.nodes) {
node.marker = DONE_MAYBE_ROOT_CYCLE_MARKER;
}
rootCycles.add(cycle);
} else {
selectedNode.marker = DONE_AND_ROOT_MARKER;
roots.add(selectedNode);
}
}
}
// Extract roots from root cycles
// We take the nodes with most incoming edges
// inside of the cycle
for (const cycle of rootCycles) {
let max = 0;
/** @type {Set<Node<T>>} */
const cycleRoots = new Set();
const nodes = cycle.nodes;
for (const node of nodes) {
for (const dep of node.dependencies) {
if (nodes.has(dep)) {
dep.incoming++;
if (dep.incoming < max) continue;
if (dep.incoming > max) {
cycleRoots.clear();
max = dep.incoming;
}
cycleRoots.add(dep);
}
}
}
for (const cycleRoot of cycleRoots) {
roots.add(cycleRoot);
}
}
// When roots were found, return them
if (roots.size > 0) {
return Array.from(roots, r => r.item);
} else {
throw new Error("Implementation of findGraphRoots is broken");
}
};