add cache.idleTimeout option to delay cache storing

declarations/WebpackOptions.d.ts

@@ -431,6 +431,10 @@ export interface FileCacheOptions {
 	 * Algorithm used for generation the hash (see node.js crypto package)
 	 */
 	hashAlgorithm?: string;
+	/**
+	 * Time in ms after which idle period cache storing should happen (only for store: 'pack' or 'idle')
+	 */
+	idleTimeout?: number;
 	/**
 	 * Display log info. (debug: all access and errors with stack trace, verbose: all access, info: all write access, warning: only failed serialization)
 	 */

lib/cache/FileCachePlugin.js

@@ -126,6 +126,7 @@ class FileCachePlugin {
 			? { debug: 4, verbose: 3, info: 2, warning: 1 }[this.options.loglevel]
 			: 0;
 		const store = this.options.store || "pack";
+		const idleTimeout = this.options.idleTimeout || 0;
 
 		const resolvedPromise = Promise.resolve();
 
@@ -364,11 +365,19 @@ class FileCachePlugin {
 				}
 			}
 		};
+		let idleTimer = undefined;
 		compiler.cache.hooks.beginIdle.tap("FileCachePlugin", () => {
-			isIdle = true;
-			resolvedPromise.then(processIdleTasks);
+			idleTimer = setTimeout(() => {
+				idleTimer = undefined;
+				isIdle = true;
+				resolvedPromise.then(processIdleTasks);
+			}, idleTimeout);
 		});
 		compiler.cache.hooks.endIdle.tap("FileCachePlugin", () => {
+			if (idleTimer) {
+				clearTimeout(idleTimer);
+				idleTimer = undefined;
+			}
 			isIdle = false;
 		});
 	}

schemas/WebpackOptions.json

@@ -168,6 +168,11 @@
           "description": "Algorithm used for generation the hash (see node.js crypto package)",
           "type": "string"
         },
+        "idleTimeout": {
+          "description": "Time in ms after which idle period cache storing should happen (only for store: 'pack' or 'idle')",
+          "type": "number",
+          "minimum": 0
+        },
         "loglevel": {
           "description": "Display log info. (debug: all access and errors with stack trace, verbose: all access, info: all write access, warning: only failed serialization)",
           "enum": ["debug", "verbose", "info", "warning"]