fix bug where module size is added multiple times to the split chunk …

…info

fixes webpack#12307

lib/optimize/SplitChunksPlugin.js

@@ -523,10 +523,14 @@ module.exports = class SplitChunksPlugin {
 								})
 							);
 						}
+						const oldSize = info.modules.size;
 						info.modules.add(module);
-						info.size += module.size();
-						if (!info.chunksKeys.has(selectedChunksKey)) {
-							info.chunksKeys.add(selectedChunksKey);
+						if (info.modules.size !== oldSize) {
+							info.size += module.size();
+						}
+						const oldChunksKeysSize = info.chunksKeys.size;
+						info.chunksKeys.add(selectedChunksKey);
+						if (oldChunksKeysSize !== info.chunksKeys.size) {
 							for (const chunk of selectedChunks) {
 								info.chunks.add(chunk);
 							}

test/ConfigTestCases.test.js

@@ -207,6 +207,7 @@ describe("ConfigTestCases", () => {
 												expect,
 												jest,
 												_globalAssign: { expect },
+												__STATS__: jsonStats,
 												nsObj: m => {
 													Object.defineProperty(m, Symbol.toStringTag, {
 														value: "Module"

test/configCases/split-chunks/issue-12307/a.js

@@ -0,0 +1,2 @@
+import "./a-only-module";
+import "./shared-module";

test/configCases/split-chunks/issue-12307/b.js

@@ -0,0 +1 @@
+import(/* webpackChunkName: "shared-module" */ "./shared-module");

test/configCases/split-chunks/issue-12307/index.js

@@ -0,0 +1,4 @@
+it("should not split the shared-modules into a separate chunk", () => {
+	const shared = __STATS__.modules.find(m => m.name.includes("shared-module"));
+	expect(shared.chunks).toEqual(["a", "shared-module"]);
+});

test/configCases/split-chunks/issue-12307/shared-module.js

@@ -0,0 +1 @@
+// content content content content content content content content content

test/configCases/split-chunks/issue-12307/webpack.config.js

@@ -0,0 +1,27 @@
+/** @type {import("../../../../").Configuration} */
+module.exports = {
+	entry: {
+		bundle0: "./index",
+		a: "./a",
+		b: "./b"
+	},
+	output: {
+		filename: "[name].js"
+	},
+	optimization: {
+		chunkIds: "named",
+		sideEffects: false,
+		splitChunks: {
+			cacheGroups: {
+				default: false,
+				defaultVendors: false,
+				test: {
+					test: /shared/,
+					minChunks: 1,
+					chunks: "initial",
+					minSize: 100
+				}
+			}
+		}
+	}
+};