Merge pull request #12915 from webpack/bugfix/multi-compiler-dependen…

…cies

fix race condition in MultiCompiler queueing

lib/MultiCompiler.js

@@ -318,7 +318,18 @@ module.exports = class MultiCompiler {
 	 * @returns {SetupResult[]} result of setup
 	 */
 	_runGraph(setup, run, callback) {
-		/** @typedef {{ compiler: Compiler, result: Stats, state: "blocked" | "queued" | "running" | "done", children: Node[], parents: Node[] }} Node */
+		/** @typedef {{ compiler: Compiler, result: Stats, state: "pending" | "blocked" | "queued" | "running" | "running-outdated" | "done", children: Node[], parents: Node[] }} Node */
+
+		// State transitions for nodes:
+		// -> blocked (initial)
+		// blocked -> queued [add to queue] (when all parents done)
+		// queued -> running [running++] (when processing the queue)
+		// running -> done [running--] (when compilation is done)
+		// done -> pending (when invalidated from file change)
+		// pending -> blocked (when invalidated from aggregated changes)
+		// done -> blocked (when invalidated, from parent invalidation)
+		// running -> running-outdated (when invalidated, either from change or parent invalidation)
+		// running-outdated -> blocked [running--] (when compilation is done)
 
 		/** @type {Node[]} */
 		const nodes = this.compilers.map(compiler => ({
@@ -376,26 +387,41 @@ module.exports = class MultiCompiler {
 			running--;
 			if (node.state === "running") {
 				node.state = "done";
-			}
-			for (const child of node.children) {
-				if (child.state !== "blocked") continue;
-				if (child.parents.every(p => p.state === "done")) {
-					child.state = "queued";
-					queue.enqueue(child);
+				for (const child of node.children) {
+					checkUnblocked(child);
 				}
+			} else if (node.state === "running-outdated") {
+				node.state = "blocked";
+				checkUnblocked(node);
 			}
 			process.nextTick(processQueue);
 		};
 		/**
 		 * @param {Node} node node
 		 * @returns {void}
 		 */
-		const nodeInvalid = node => {
-			if (node.state === "done" || node.state === "running") {
+		const nodeInvalidFromParent = node => {
+			if (node.state === "done") {
 				node.state = "blocked";
+			} else if (node.state === "running") {
+				node.state = "running-outdated";
 			}
 			for (const child of node.children) {
-				nodeInvalid(child);
+				nodeInvalidFromParent(child);
+			}
+		};
+		/**
+		 * @param {Node} node node
+		 * @returns {void}
+		 */
+		const nodeInvalid = node => {
+			if (node.state === "done") {
+				node.state = "pending";
+			} else if (node.state === "running") {
+				node.state = "running-outdated";
+			}
+			for (const child of node.children) {
+				nodeInvalidFromParent(child);
 			}
 		};
 		/**
@@ -404,23 +430,34 @@ module.exports = class MultiCompiler {
 		 */
 		const nodeChange = node => {
 			nodeInvalid(node);
+			if (node.state === "pending") {
+				node.state = "blocked";
+			}
+			checkUnblocked(node);
+			processQueue();
+		};
+		/**
+		 * @param {Node} node node
+		 * @returns {void}
+		 */
+		const checkUnblocked = node => {
 			if (
 				node.state === "blocked" &&
 				node.parents.every(p => p.state === "done")
 			) {
 				node.state = "queued";
 				queue.enqueue(node);
-				processQueue();
 			}
 		};
+
 		const setupResults = [];
 		nodes.forEach((node, i) => {
 			setupResults.push(
 				setup(
 					node.compiler,
 					i,
 					nodeDone.bind(null, node),
-					() => node.state === "blocked" || node.state === "queued",
+					() => node.state !== "running",
 					() => nodeChange(node),
 					() => nodeInvalid(node)
 				)
@@ -434,7 +471,11 @@ module.exports = class MultiCompiler {
 				node.state = "running";
 				run(node.compiler, nodeDone.bind(null, node));
 			}
-			if (!errored && running === 0) {
+			if (
+				!errored &&
+				running === 0 &&
+				nodes.every(node => node.state === "done")
+			) {
 				const stats = [];
 				for (const node of nodes) {
 					const result = node.result;

test/MultiCompiler.test.js

@@ -363,4 +363,50 @@ describe("MultiCompiler", function () {
 			}
 		});
 	});
+	it("shouldn't hang when invalidating during build", done => {
+		const compiler = webpack(
+			Object.assign([
+				{
+					name: "a",
+					mode: "development",
+					context: path.join(__dirname, "fixtures"),
+					entry: "./a.js"
+				},
+				{
+					name: "b",
+					mode: "development",
+					context: path.join(__dirname, "fixtures"),
+					entry: "./b.js",
+					dependencies: ["a"]
+				}
+			])
+		);
+		compiler.outputFileSystem = createFsFromVolume(new Volume());
+		const watchCallbacks = [];
+		const watchCallbacksUndelayed = [];
+		let firstRun = true;
+		compiler.watchFileSystem = {
+			watch(
+				files,
+				directories,
+				missing,
+				startTime,
+				options,
+				callback,
+				callbackUndelayed
+			) {
+				watchCallbacks.push(callback);
+				watchCallbacksUndelayed.push(callbackUndelayed);
+				if (firstRun && files.has(path.join(__dirname, "fixtures", "a.js"))) {
+					process.nextTick(() => {
+						callback(null, new Map(), new Map(), new Set(), new Set());
+					});
+					firstRun = false;
+				}
+			}
+		};
+		compiler.watch({}, (err, stats) => {
+			done(err);
+		});
+	});
 });