enable optimization.sideEffects by default

lib/WebpackOptionsDefaulter.js

@@ -363,9 +363,7 @@ class WebpackOptionsDefaulter extends OptionsDefaulter {
 			if (options.mode === "development") return "named";
 			return "natural";
 		});
-		this.set("optimization.sideEffects", "make", options =>
-			isProductionLikeMode(options)
-		);
+		this.set("optimization.sideEffects", true);
 		this.set("optimization.providedExports", true);
 		this.set("optimization.usedExports", "make", options =>
 			isProductionLikeMode(options)

test/WebpackOptionsDefaulter.unittest.js

@@ -141,7 +141,7 @@ describe("WebpackOptionsDefaulter", () => {
 		    "removeAvailableModules": false,
 		    "removeEmptyChunks": true,
 		    "runtimeChunk": undefined,
-		    "sideEffects": false,
+		    "sideEffects": true,
 		    "splitChunks": Object {
 		      "automaticNameDelimiter": "-",
 		      "cacheGroups": Object {
@@ -289,9 +289,6 @@ describe("WebpackOptionsDefaulter", () => {
 		+     "moduleIds": "deterministic",
 		+     "noEmitOnErrors": true,
 		+     "nodeEnv": "production",
-		@@ -76,1 +76,1 @@
-		-     "sideEffects": false,
-		+     "sideEffects": true,
 		@@ -94,3 +94,3 @@
 		-       "hidePathInfo": false,
 		-       "maxAsyncRequests": Infinity,
@@ -345,9 +342,6 @@ describe("WebpackOptionsDefaulter", () => {
 		+     "moduleIds": "deterministic",
 		+     "noEmitOnErrors": true,
 		+     "nodeEnv": "production",
-		@@ -76,1 +76,1 @@
-		-     "sideEffects": false,
-		+     "sideEffects": true,
 		@@ -94,3 +94,3 @@
 		-       "hidePathInfo": false,
 		-       "maxAsyncRequests": Infinity,