add logging

lib/watchEventSource.js

@@ -16,6 +16,9 @@ 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;
 
@@ -93,12 +96,28 @@ class RecursiveWatcher {
 			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));
@@ -118,6 +137,11 @@ class RecursiveWatcher {
 			});
 		}
 		watcherCount++;
+		if (recursiveWatcherLogging) {
+			process.stderr.write(
+				`[watchpack] created recursive watcher at ${rootPath}\n`
+			);
+		}
 	}
 
 	add(filePath, watcher) {
@@ -147,6 +171,11 @@ class RecursiveWatcher {
 			recursiveWatchers.delete(this.rootPath);
 			watcherCount--;
 			if (this.watcher) this.watcher.close();
+			if (recursiveWatcherLogging) {
+				process.stderr.write(
+					`[watchpack] closed recursive watcher at ${this.rootPath}\n`
+				);
+			}
 		}
 	}