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watchEventSource.js
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Wed, Nov 13, 04:34

watchEventSource.js
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/*
MIT License http://www.opensource.org/licenses/mit-license.php
Author Tobias Koppers @sokra
*/
"use strict";
const fs = require("fs");
const path = require("path");
const { EventEmitter } = require("events");
const reducePlan = require("./reducePlan");
const IS_OSX = require("os").platform() === "darwin";
const IS_WIN = require("os").platform() === "win32";
const SUPPORTS_RECURSIVE_WATCHING = IS_OSX || IS_WIN;
const watcherLimit =
+process.env.WATCHPACK_WATCHER_LIMIT || (IS_OSX ? 2000 : 10000);
const recursiveWatcherLogging = !!process.env
.WATCHPACK_RECURSIVE_WATCHER_LOGGING;
let isBatch = false;
let watcherCount = 0;
/** @type {Map<Watcher, string>} */
const pendingWatchers = new Map();
/** @type {Map<string, RecursiveWatcher>} */
const recursiveWatchers = new Map();
/** @type {Map<string, DirectWatcher>} */
const directWatchers = new Map();
/** @type {Map<Watcher, RecursiveWatcher | DirectWatcher>} */
const underlyingWatcher = new Map();
class DirectWatcher {
constructor(filePath) {
this.filePath = filePath;
this.watchers = new Set();
this.watcher = undefined;
try {
const watcher = fs.watch(filePath);
this.watcher = watcher;
watcher.on("change", (type, filename) => {
for (const w of this.watchers) {
w.emit("change", type, filename);
}
});
watcher.on("error", error => {
for (const w of this.watchers) {
w.emit("error", error);
}
});
} catch (err) {
process.nextTick(() => {
for (const w of this.watchers) {
w.emit("error", err);
}
});
}
watcherCount++;
}
add(watcher) {
underlyingWatcher.set(watcher, this);
this.watchers.add(watcher);
}
remove(watcher) {
this.watchers.delete(watcher);
if (this.watchers.size === 0) {
directWatchers.delete(this.filePath);
watcherCount--;
if (this.watcher) this.watcher.close();
}
}
getWatchers() {
return this.watchers;
}
}
class RecursiveWatcher {
constructor(rootPath) {
this.rootPath = rootPath;
/** @type {Map<Watcher, string>} */
this.mapWatcherToPath = new Map();
/** @type {Map<string, Set<Watcher>>} */
this.mapPathToWatchers = new Map();
this.watcher = undefined;
try {
const watcher = fs.watch(rootPath, {
recursive: true
});
this.watcher = watcher;
watcher.on("change", (type, filename) => {
if (!filename) {
if (recursiveWatcherLogging) {
process.stderr.write(
`[watchpack] dispatch ${type} event in recursive watcher (${
this.rootPath
}) to all watchers\n`
);
}
for (const w of this.mapWatcherToPath.keys()) {
w.emit("change", type);
}
} else {
const dir = path.dirname(filename);
const watchers = this.mapPathToWatchers.get(dir);
if (recursiveWatcherLogging) {
process.stderr.write(
`[watchpack] dispatch ${type} event in recursive watcher (${
this.rootPath
}) for '${filename}' to ${
watchers ? watchers.size : 0
} watchers\n`
);
}
if (watchers === undefined) return;
for (const w of watchers) {
w.emit("change", type, path.basename(filename));
}
}
});
watcher.on("error", error => {
for (const w of this.mapWatcherToPath.keys()) {
w.emit("error", error);
}
});
} catch (err) {
process.nextTick(() => {
for (const w of this.mapWatcherToPath.keys()) {
w.emit("error", err);
}
});
}
watcherCount++;
if (recursiveWatcherLogging) {
process.stderr.write(
`[watchpack] created recursive watcher at ${rootPath}\n`
);
}
}
add(filePath, watcher) {
underlyingWatcher.set(watcher, this);
const subpath = filePath.slice(this.rootPath.length + 1) || ".";
this.mapWatcherToPath.set(watcher, subpath);
const set = this.mapPathToWatchers.get(subpath);
if (set === undefined) {
const newSet = new Set();
newSet.add(watcher);
this.mapPathToWatchers.set(subpath, newSet);
} else {
set.add(watcher);
}
}
remove(watcher) {
const subpath = this.mapWatcherToPath.get(watcher);
if (!subpath) return;
this.mapWatcherToPath.delete(watcher);
const set = this.mapPathToWatchers.get(subpath);
set.delete(watcher);
if (set.size === 0) {
this.mapPathToWatchers.delete(subpath);
}
if (this.mapWatcherToPath.size === 0) {
recursiveWatchers.delete(this.rootPath);
watcherCount--;
if (this.watcher) this.watcher.close();
if (recursiveWatcherLogging) {
process.stderr.write(
`[watchpack] closed recursive watcher at ${this.rootPath}\n`
);
}
}
}
getWatchers() {
return this.mapWatcherToPath;
}
}
class Watcher extends EventEmitter {
close() {
if (pendingWatchers.has(this)) {
pendingWatchers.delete(this);
return;
}
const watcher = underlyingWatcher.get(this);
watcher.remove(this);
underlyingWatcher.delete(this);
}
}
const createDirectWatcher = filePath => {
const existing = directWatchers.get(filePath);
if (existing !== undefined) return existing;
const w = new DirectWatcher(filePath);
directWatchers.set(filePath, w);
return w;
};
const createRecursiveWatcher = rootPath => {
const existing = recursiveWatchers.get(rootPath);
if (existing !== undefined) return existing;
const w = new RecursiveWatcher(rootPath);
recursiveWatchers.set(rootPath, w);
return w;
};
const execute = () => {
/** @type {Map<string, Watcher[] | Watcher>} */
const map = new Map();
const addWatcher = (watcher, filePath) => {
const entry = map.get(filePath);
if (entry === undefined) {
map.set(filePath, watcher);
} else if (Array.isArray(entry)) {
entry.push(watcher);
} else {
map.set(filePath, [entry, watcher]);
}
};
for (const [watcher, filePath] of pendingWatchers) {
addWatcher(watcher, filePath);
}
pendingWatchers.clear();
// Fast case when we are not reaching the limit
if (!SUPPORTS_RECURSIVE_WATCHING || watcherLimit - watcherCount >= map.size) {
// Create watchers for all entries in the map
for (const [filePath, entry] of map) {
const w = createDirectWatcher(filePath);
if (Array.isArray(entry)) {
for (const item of entry) w.add(item);
} else {
w.add(entry);
}
}
return;
}
// Reconsider existing watchers to improving watch plan
for (const watcher of recursiveWatchers.values()) {
for (const [w, subpath] of watcher.getWatchers()) {
addWatcher(w, path.join(watcher.rootPath, subpath));
}
}
for (const watcher of directWatchers.values()) {
for (const w of watcher.getWatchers()) {
addWatcher(w, watcher.filePath);
}
}
// Merge map entries to keep watcher limit
// Create a 10% buffer to be able to enter fast case more often
const plan = reducePlan(map, watcherLimit * 0.9);
// Update watchers for all entries in the map
for (const [filePath, entry] of plan) {
if (entry.size === 1) {
for (const [watcher, filePath] of entry) {
const w = createDirectWatcher(filePath);
const old = underlyingWatcher.get(watcher);
if (old === w) continue;
w.add(watcher);
if (old !== undefined) old.remove(watcher);
}
} else {
const filePaths = new Set(entry.values());
if (filePaths.size > 1) {
const w = createRecursiveWatcher(filePath);
for (const [watcher, watcherPath] of entry) {
const old = underlyingWatcher.get(watcher);
if (old === w) continue;
w.add(watcherPath, watcher);
if (old !== undefined) old.remove(watcher);
}
} else {
for (const filePath of filePaths) {
const w = createDirectWatcher(filePath);
for (const watcher of entry.keys()) {
const old = underlyingWatcher.get(watcher);
if (old === w) continue;
w.add(watcher);
if (old !== undefined) old.remove(watcher);
}
}
}
}
}
};
exports.watch = filePath => {
const watcher = new Watcher();
// Find an existing watcher
const directWatcher = directWatchers.get(filePath);
if (directWatcher !== undefined) {
directWatcher.add(watcher);
return watcher;
}
let current = filePath;
for (;;) {
const recursiveWatcher = recursiveWatchers.get(current);
if (recursiveWatcher !== undefined) {
recursiveWatcher.add(filePath, watcher);
return watcher;
}
const parent = path.dirname(current);
if (parent === current) break;
current = parent;
}
// Queue up watcher for creation
pendingWatchers.set(watcher, filePath);
if (!isBatch) execute();
return watcher;
};
exports.batch = fn => {
isBatch = true;
try {
fn();
} finally {
isBatch = false;
execute();
}
};
exports.getNumberOfWatchers = () => {
return watcherCount;
};

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