From 3554793b4ba23d1173685b8cfa277b5bbadd0d74 Mon Sep 17 00:00:00 2001
From: Tobias Koppers <tobias.koppers@googlemail.com>
Date: Thu, 7 Jan 2021 16:51:08 +0100
Subject: [PATCH 1/2] fix bug where module size is added multiple times to the
 split chunk info

fixes #12307
---
 lib/optimize/SplitChunksPlugin.js             | 12 +++++---
 .../split-chunks/issue-12307/a-only-module.js |  0
 .../configCases/split-chunks/issue-12307/a.js |  2 ++
 .../configCases/split-chunks/issue-12307/b.js |  1 +
 .../split-chunks/issue-12307/index.js         |  4 +++
 .../split-chunks/issue-12307/shared-module.js |  1 +
 .../issue-12307/webpack.config.js             | 29 +++++++++++++++++++
 7 files changed, 45 insertions(+), 4 deletions(-)
 create mode 100644 test/configCases/split-chunks/issue-12307/a-only-module.js
 create mode 100644 test/configCases/split-chunks/issue-12307/a.js
 create mode 100644 test/configCases/split-chunks/issue-12307/b.js
 create mode 100644 test/configCases/split-chunks/issue-12307/index.js
 create mode 100644 test/configCases/split-chunks/issue-12307/shared-module.js
 create mode 100644 test/configCases/split-chunks/issue-12307/webpack.config.js

diff --git a/lib/optimize/SplitChunksPlugin.js b/lib/optimize/SplitChunksPlugin.js
index edca93f24..ba04347c0 100644
--- a/lib/optimize/SplitChunksPlugin.js
+++ b/lib/optimize/SplitChunksPlugin.js
@@ -1113,12 +1113,16 @@ module.exports = class SplitChunksPlugin {
 								})
 							);
 						}
+						const oldSize = info.modules.size;
 						info.modules.add(module);
-						for (const type of module.getSourceTypes()) {
-							info.sizes[type] = (info.sizes[type] || 0) + module.size(type);
+						if (info.modules.size !== oldSize) {
+							for (const type of module.getSourceTypes()) {
+								info.sizes[type] = (info.sizes[type] || 0) + module.size(type);
+							}
 						}
-						if (!info.chunksKeys.has(selectedChunksKey)) {
-							info.chunksKeys.add(selectedChunksKey);
+						const oldChunksKeysSize = info.chunksKeys.size;
+						info.chunksKeys.add(selectedChunksKey);
+						if (oldChunksKeysSize !== info.chunksKeys.size) {
 							for (const chunk of selectedChunks) {
 								info.chunks.add(chunk);
 							}
diff --git a/test/configCases/split-chunks/issue-12307/a-only-module.js b/test/configCases/split-chunks/issue-12307/a-only-module.js
new file mode 100644
index 000000000..e69de29bb
diff --git a/test/configCases/split-chunks/issue-12307/a.js b/test/configCases/split-chunks/issue-12307/a.js
new file mode 100644
index 000000000..62ba2bbb4
--- /dev/null
+++ b/test/configCases/split-chunks/issue-12307/a.js
@@ -0,0 +1,2 @@
+import "./a-only-module";
+import "./shared-module";
diff --git a/test/configCases/split-chunks/issue-12307/b.js b/test/configCases/split-chunks/issue-12307/b.js
new file mode 100644
index 000000000..181dd93c0
--- /dev/null
+++ b/test/configCases/split-chunks/issue-12307/b.js
@@ -0,0 +1 @@
+import("./shared-module");
diff --git a/test/configCases/split-chunks/issue-12307/index.js b/test/configCases/split-chunks/issue-12307/index.js
new file mode 100644
index 000000000..4ca0b89ec
--- /dev/null
+++ b/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_js"]);
+});
diff --git a/test/configCases/split-chunks/issue-12307/shared-module.js b/test/configCases/split-chunks/issue-12307/shared-module.js
new file mode 100644
index 000000000..9cc8c7e2f
--- /dev/null
+++ b/test/configCases/split-chunks/issue-12307/shared-module.js
@@ -0,0 +1 @@
+// content content content content content content content content content
diff --git a/test/configCases/split-chunks/issue-12307/webpack.config.js b/test/configCases/split-chunks/issue-12307/webpack.config.js
new file mode 100644
index 000000000..9b3b9ad5d
--- /dev/null
+++ b/test/configCases/split-chunks/issue-12307/webpack.config.js
@@ -0,0 +1,29 @@
+/** @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,
+					usedExports: false,
+					chunks: "initial",
+					minSize: 100,
+					minRemainingSize: 0
+				}
+			}
+		}
+	}
+};

From 35c7801b5e5320b0830e84ca10a3dfdab0999847 Mon Sep 17 00:00:00 2001
From: Tobias Koppers <tobias.koppers@googlemail.com>
Date: Thu, 7 Jan 2021 21:47:08 +0100
Subject: [PATCH 2/2] fix bug where cacheGroup index was inverted

---
 lib/optimize/SplitChunksPlugin.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/optimize/SplitChunksPlugin.js b/lib/optimize/SplitChunksPlugin.js
index ba04347c0..9b1ae3399 100644
--- a/lib/optimize/SplitChunksPlugin.js
+++ b/lib/optimize/SplitChunksPlugin.js
@@ -232,7 +232,7 @@ const compareEntries = (a, b) => {
 	const diffSizeReduce = aSizeReduce - bSizeReduce;
 	if (diffSizeReduce) return diffSizeReduce;
 	// 4. by cache group index
-	const indexDiff = a.cacheGroupIndex - b.cacheGroupIndex;
+	const indexDiff = b.cacheGroupIndex - a.cacheGroupIndex;
 	if (indexDiff) return indexDiff;
 	// 5. by number of modules (to be able to compare by identifier)
 	const modulesA = a.modules;