improved tree shaking for star exports

fixes #3415

lib/MainTemplate.js

@@ -120,6 +120,8 @@ function MainTemplate(outputOptions) {
 		buf.push("// define getter function for harmory exports");
 		buf.push(this.requireFn + ".d = function(exports, name, getter) {");
 		buf.push(this.indent([
+			"if(!" + this.requireFn + ".o(exports, name)) {",
+			this.indent([
 				"Object.defineProperty(exports, name, {",
 				this.indent([
 					"configurable: false,",
@@ -127,6 +129,8 @@ function MainTemplate(outputOptions) {
 					"get: getter"
 				]),
 				"});"
+			]),
+			"}"
 		]));
 		buf.push("};");
 

lib/dependencies/HarmonyExportImportedSpecifierDependency.js

@@ -30,7 +30,7 @@ HarmonyExportImportedSpecifierDependency.prototype.getReference = function() {
 		// export *
 		if(Array.isArray(this.originModule.usedExports)) {
 			// reexport * with known used exports
-			var activeExports = HarmonyModulesHelpers.getActiveExports(this.originModule);
+			var activeExports = HarmonyModulesHelpers.getActiveExports(this.originModule, this);
 			if(Array.isArray(m.providedExports)) {
 				return {
 					module: m,
@@ -108,6 +108,14 @@ HarmonyExportImportedSpecifierDependency.prototype.getExports = function() {
 };
 
 HarmonyExportImportedSpecifierDependency.prototype.describeHarmonyExport = function() {
+	var importedModule = this.importDependency.module;
+	if(!this.name && importedModule && Array.isArray(importedModule.providedExports)) {
+		// for a star export and when we know which exports are provided, we can tell so
+		return {
+			exportedName: importedModule.providedExports,
+			precedence: 3
+		}
+	}
 	return {
 		exportedName: this.name,
 		precedence: this.name ? 2 : 3
@@ -149,7 +157,7 @@ HarmonyExportImportedSpecifierDependency.Template.prototype.apply = function(dep
 	} else if(dep.name) { // we want to reexport the module object as named export
 		content = "/* harmony reexport (module object) */ " + getReexportStatement(JSON.stringify(used), "");
 	} else if(Array.isArray(dep.originModule.usedExports)) { // we know which exports are used
-		activeExports = HarmonyModulesHelpers.getActiveExports(dep.originModule);
+		activeExports = HarmonyModulesHelpers.getActiveExports(dep.originModule, dep);
 		items = dep.originModule.usedExports.map(function(id) {
 			if(id === "default") return;
 			if(activeExports.indexOf(id) >= 0) return;
@@ -164,7 +172,7 @@ HarmonyExportImportedSpecifierDependency.Template.prototype.apply = function(dep
 			}).join("");
 		} else content = "/* unused harmony namespace reexport */\n";
 	} else if(dep.originModule.usedExports && importedModule && Array.isArray(importedModule.providedExports)) { // not sure which exports are used, but we know which are provided
-		activeExports = HarmonyModulesHelpers.getActiveExports(dep.originModule);
+		activeExports = HarmonyModulesHelpers.getActiveExports(dep.originModule, dep);
 		items = importedModule.providedExports.map(function(id) {
 			if(id === "default") return;
 			if(activeExports.indexOf(id) >= 0) return;
@@ -178,7 +186,7 @@ HarmonyExportImportedSpecifierDependency.Template.prototype.apply = function(dep
 			}).join("");
 		} else content = "/* empty harmony namespace reexport */\n";
 	} else if(dep.originModule.usedExports) { // not sure which exports are used and provided
-		activeExports = HarmonyModulesHelpers.getActiveExports(dep.originModule);
+		activeExports = HarmonyModulesHelpers.getActiveExports(dep.originModule, dep);
 		content = "/* harmony namespace reexport (unknown) */ for(var __WEBPACK_IMPORT_KEY__ in " + name + ") ";
 
 		// Filter out exports which are defined by other exports

lib/dependencies/HarmonyModulesHelpers.js

@@ -55,16 +55,26 @@ HarmonyModulesHelpers.isActive = function(module, depInQuestion) {
 
 // get a list of named exports defined in a module
 // doesn't include * reexports.
-HarmonyModulesHelpers.getActiveExports = function(module) {
+HarmonyModulesHelpers.getActiveExports = function(module, currentDependency) {
-	if(module.activeExports)
+	var desc = currentDependency && currentDependency.describeHarmonyExport();
-		return module.activeExports;
+	var currentIndex = currentDependency ? module.dependencies.indexOf(currentDependency) : -1;
-	return module.dependencies.reduce(function(arr, dep) {
+	return module.dependencies.map(function(dep, idx) {
+		return {
+			dep: dep,
+			idx: idx
+		}
+	}).reduce(function(arr, data) {
+		var dep = data.dep;
 		if(!dep.describeHarmonyExport) return arr;
 		var d = dep.describeHarmonyExport();
 		if(!d) return arr;
-		var name = d.exportedName;
+		if(!desc || (d.precedence < desc.precedence) || (d.precedence === desc.precedence && data.idx < currentIndex)) {
-		if(!name || arr.indexOf(name) >= 0) return arr;
+			var names = [].concat(d.exportedName);
+			names.forEach(function(name) {
+				if(name && arr.indexOf(name) < 0)
 					arr.push(name);
+			});
+		}
 		return arr;
-	}, [])
+	}, []);
 };

test/cases/parsing/harmony-duplicate-export/1.js

@@ -0,0 +1,2 @@
+export var x = "1";
+export * from "./a";

test/cases/parsing/harmony-duplicate-export/2.js

@@ -0,0 +1,2 @@
+export * from "./a";
+export var x = "1";

test/cases/parsing/harmony-duplicate-export/3.js

@@ -0,0 +1,2 @@
+export * from "./a";
+export * from "./b";

test/cases/parsing/harmony-duplicate-export/4.js

@@ -0,0 +1,2 @@
+export * from "./b";
+export * from "./a";

test/cases/parsing/harmony-duplicate-export/5.js

@@ -0,0 +1,2 @@
+export * from "./c";
+export * from "./d";

test/cases/parsing/harmony-duplicate-export/6.js

@@ -0,0 +1,4 @@
+export * from "./a";
+export * from "./b";
+export * from "./c";
+export * from "./d";

test/cases/parsing/harmony-duplicate-export/7.js

@@ -0,0 +1,4 @@
+export * from "./d";
+export * from "./b";
+export * from "./c";
+export * from "./a";

test/cases/parsing/harmony-duplicate-export/a.js

@@ -0,0 +1 @@
+export var x = "a";

test/cases/parsing/harmony-duplicate-export/b.js

@@ -0,0 +1 @@
+export var x = "b";

test/cases/parsing/harmony-duplicate-export/c.js

@@ -0,0 +1 @@
+exports.x = "c";

test/cases/parsing/harmony-duplicate-export/d.js

@@ -0,0 +1 @@
+exports.x = "d";

test/cases/parsing/harmony-duplicate-export/index.js

@@ -0,0 +1,35 @@
+import { x as x1 } from "./1?a";
+import { x as x2 } from "./2?a";
+import { x as x3 } from "./3?a";
+import { x as x4 } from "./4?a";
+import { x as x5 } from "./5?a";
+import { x as x6 } from "./6?a";
+import { x as x7 } from "./7?a";
+
+var y1 = require("./1?b").x;
+var y2 = require("./2?b").x;
+var y3 = require("./3?b").x;
+var y4 = require("./4?b").x;
+var y5 = require("./5?b").x;
+var y6 = require("./6?b").x;
+var y7 = require("./7?b").x;
+
+it("should not overwrite when using star export (known exports)", function() {
+	x1.should.be.eql("1");
+	x2.should.be.eql("1");
+	x3.should.be.eql("a");
+	x4.should.be.eql("b");
+	x5.should.be.eql("c");
+	x6.should.be.eql("a");
+	x7.should.be.eql("d");
+});
+
+it("should not overwrite when using star export (unknown exports)", function() {
+	y1.should.be.eql("1");
+	y2.should.be.eql("1");
+	y3.should.be.eql("a");
+	y4.should.be.eql("b");
+	y5.should.be.eql("c");
+	y6.should.be.eql("a");
+	y7.should.be.eql("d");
+});

test/cases/parsing/harmony-duplicate-export/reexport.js

@@ -0,0 +1 @@
+export * from "./a";

test/statsCases/aggressive-splitting-entry/expected.txt

@@ -1,7 +1,7 @@
 Hash: 8e46421d7f7a7d266a00
 Time: Xms
                   Asset       Size  Chunks             Chunk Names
-48c8b1dae03a37363ec8.js    4.17 kB       1  [emitted]  
+48c8b1dae03a37363ec8.js    4.24 kB       1  [emitted]  
 2fa7af5012a3d8b778dd.js    2.22 kB       2  [emitted]  
 a5b577236621262c2bcf.js    1.93 kB       3  [emitted]  
 88d78642a86768757078.js  977 bytes       4  [emitted]  

test/statsCases/aggressive-splitting-on-demand/expected.txt

@@ -6,7 +6,7 @@ Time: Xms
 5ae9e18455b866684bd0.js    1.94 kB       2  [emitted]  
 e91ec4902ca3057b42bb.js    1.93 kB       3  [emitted]  
 0947f0875d56ab0bfe02.js  977 bytes       4  [emitted]  
-6335d9dcc7fa048743b7.js    7.13 kB       6  [emitted]  main
+6335d9dcc7fa048743b7.js     7.2 kB       6  [emitted]  main
 cf500be0e585f01d2ccb.js  983 bytes       9  [emitted]  
 a7bfb642a544b4302cc4.js  975 bytes      11  [emitted]  
 Entrypoint main = 6335d9dcc7fa048743b7.js

test/statsCases/chunks/expected.txt

@@ -4,7 +4,7 @@ Time: Xms
 0.bundle.js  227 bytes       0  [emitted]  
 1.bundle.js  106 bytes       1  [emitted]  
 2.bundle.js  200 bytes       2  [emitted]  
-  bundle.js    5.77 kB       3  [emitted]  main
+  bundle.js    5.84 kB       3  [emitted]  main
 chunk    {0} 0.bundle.js 54 bytes {3} [rendered]
     > [5] (webpack)/test/statsCases/chunks/index.js 3:0-16
     [2] (webpack)/test/statsCases/chunks/c.js 54 bytes {0} [built]

test/statsCases/color-disabled/expected.txt

@@ -1,6 +1,6 @@
 Hash: 6c781fe6bf412ba6435b
 Time: Xms
   Asset     Size  Chunks             Chunk Names
-main.js  2.43 kB       0  [emitted]  main
+main.js  2.51 kB       0  [emitted]  main
 chunk    {0} main.js (main) 0 bytes [entry] [rendered]
     [0] (webpack)/test/statsCases/color-disabled/index.js 0 bytes {0} [built]

test/statsCases/color-enabled-custom/expected.txt

@@ -1,6 +1,6 @@
 Hash: <CLR=BOLD>6c781fe6bf412ba6435b</CLR>
 Time: <CLR=BOLD>X</CLR>ms
   <CLR=BOLD>Asset</CLR>     <CLR=BOLD>Size</CLR>  <CLR=BOLD>Chunks</CLR>  <CLR=39,BOLD><CLR=22>           <CLR=BOLD>Chunk Names</CLR>
-<CLR=32>main.js</CLR>  2.43 kB       <CLR=BOLD>0</CLR>  <CLR=32>[emitted]</CLR>  main
+<CLR=32>main.js</CLR>  2.51 kB       <CLR=BOLD>0</CLR>  <CLR=32>[emitted]</CLR>  main
 chunk    {<CLR=33>0</CLR>} <CLR=32>main.js</CLR> (main) 0 bytes<CLR=33> [entry]</CLR><CLR=32> [rendered]</CLR>
     [0] <CLR=BOLD>(webpack)/test/statsCases/color-enabled-custom/index.js</CLR> 0 bytes {<CLR=33>0</CLR>}<CLR=32> [built]</CLR>

test/statsCases/color-enabled/expected.txt

@@ -1,6 +1,6 @@
 Hash: <CLR=BOLD>6c781fe6bf412ba6435b</CLR>
 Time: <CLR=BOLD>X</CLR>ms
   <CLR=BOLD>Asset</CLR>     <CLR=BOLD>Size</CLR>  <CLR=BOLD>Chunks</CLR>  <CLR=39,BOLD><CLR=22>           <CLR=BOLD>Chunk Names</CLR>
-<CLR=32,BOLD>main.js</CLR>  2.43 kB       <CLR=BOLD>0</CLR>  <CLR=32,BOLD>[emitted]</CLR>  main
+<CLR=32,BOLD>main.js</CLR>  2.51 kB       <CLR=BOLD>0</CLR>  <CLR=32,BOLD>[emitted]</CLR>  main
 chunk    {<CLR=33,BOLD>0</CLR>} <CLR=32,BOLD>main.js</CLR> (main) 0 bytes<CLR=33,BOLD> [entry]</CLR><CLR=32,BOLD> [rendered]</CLR>
     [0] <CLR=BOLD>(webpack)/test/statsCases/color-enabled/index.js</CLR> 0 bytes {<CLR=33,BOLD>0</CLR>}<CLR=32,BOLD> [built]</CLR>

test/statsCases/define-plugin/expected.txt

@@ -3,13 +3,13 @@ Child
     Hash: 052d0451a89cb963e4d3
     Time: Xms
       Asset     Size  Chunks             Chunk Names
-    main.js  2.48 kB       0  [emitted]  main
+    main.js  2.55 kB       0  [emitted]  main
     chunk    {0} main.js (main) 24 bytes [entry] [rendered]
         [0] (webpack)/test/statsCases/define-plugin/index.js 24 bytes {0} [built]
 Child
     Hash: eb3ff8e5a88b9234d04f
     Time: Xms
       Asset     Size  Chunks             Chunk Names
-    main.js  2.48 kB       0  [emitted]  main
+    main.js  2.55 kB       0  [emitted]  main
     chunk    {0} main.js (main) 24 bytes [entry] [rendered]
         [0] (webpack)/test/statsCases/define-plugin/index.js 24 bytes {0} [built]

test/statsCases/exclude-with-loader/expected.txt

@@ -1,7 +1,7 @@
 Hash: affacd3db222d3fcb700
 Time: Xms
     Asset     Size  Chunks             Chunk Names
-bundle.js  2.69 kB       0  [emitted]  main
+bundle.js  2.77 kB       0  [emitted]  main
 chunk    {0} bundle.js (main) 132 bytes [entry] [rendered]
     [0] (webpack)/test/statsCases/exclude-with-loader/a.txt 43 bytes {0} [built]
     [2] (webpack)/test/statsCases/exclude-with-loader/index.js 46 bytes {0} [built]

test/statsCases/external/expected.txt

@@ -1,7 +1,7 @@
 Hash: 5957a4911072fb217ca1
 Time: Xms
   Asset     Size  Chunks             Chunk Names
-main.js  2.57 kB       0  [emitted]  main
+main.js  2.64 kB       0  [emitted]  main
 chunk    {0} main.js (main) 59 bytes [entry] [rendered]
     [0] external "test" 42 bytes {0} [not cacheable]
     [1] (webpack)/test/statsCases/external/index.js 17 bytes {0} [built]

test/statsCases/optimize-chunks/expected.txt

@@ -8,7 +8,7 @@ Time: Xms
    4.js  136 bytes    4, 6  [emitted]  chunk
    5.js  293 bytes    5, 3  [emitted]  cir2 from cir1
    6.js   78 bytes       6  [emitted]  ac in ab
-main.js    6.37 kB       7  [emitted]  main
+main.js    6.45 kB       7  [emitted]  main
 chunk    {0} 0.js (cir1) 81 bytes {7} {5} {3} [rendered]
     > duplicate cir1 from cir2 [3] (webpack)/test/statsCases/optimize-chunks/circular2.js 1:0-79
     > duplicate cir1 [8] (webpack)/test/statsCases/optimize-chunks/index.js 13:0-54

test/statsCases/preset-verbose/expected.txt

@@ -4,7 +4,7 @@ Time: Xms
    0.js  227 bytes       0  [emitted]  
    1.js  106 bytes       1  [emitted]  
    2.js  200 bytes       2  [emitted]  
-main.js    5.76 kB       3  [emitted]  main
+main.js    5.83 kB       3  [emitted]  main
 Entrypoint main = main.js
 chunk    {0} 0.js 54 bytes {3} [rendered]
     [2] (webpack)/test/statsCases/preset-verbose/c.js 54 bytes {0} [built]

test/statsCases/separate-css-bundle/expected.txt

@@ -3,7 +3,7 @@ Child
     Hash: 9ff2cfa8882f273c8c6d
     Time: Xms
                                    Asset      Size  Chunks             Chunk Names
-                 f49aa1e6c5ada5da859b.js   2.57 kB       0  [emitted]  main
+                 f49aa1e6c5ada5da859b.js   2.65 kB       0  [emitted]  main
     c815cf440254d4f3bba4e7041db00a28.css  26 bytes       0  [emitted]  main
     chunk    {0} f49aa1e6c5ada5da859b.js, c815cf440254d4f3bba4e7041db00a28.css (main) 64 bytes [entry] [rendered]
         [0] (webpack)/test/statsCases/separate-css-bundle/a/file.css 41 bytes {0} [built]
@@ -16,7 +16,7 @@ Child
     Hash: 9ff2cfa8882f273c8c6d
     Time: Xms
                                    Asset      Size  Chunks             Chunk Names
-                 f49aa1e6c5ada5da859b.js   2.57 kB       0  [emitted]  main
+                 f49aa1e6c5ada5da859b.js   2.65 kB       0  [emitted]  main
     a3f385680aef7a9bb2a517699532cc34.css  28 bytes       0  [emitted]  main
     chunk    {0} f49aa1e6c5ada5da859b.js, a3f385680aef7a9bb2a517699532cc34.css (main) 64 bytes [entry] [rendered]
         [0] (webpack)/test/statsCases/separate-css-bundle/b/file.css 41 bytes {0} [built]

test/statsCases/simple-more-info/expected.txt

@@ -1,7 +1,7 @@
 Hash: 0bd4f09244f0e8c60354
 Time: Xms
     Asset     Size  Chunks             Chunk Names
-bundle.js  2.43 kB       0  [emitted]  main
+bundle.js  2.51 kB       0  [emitted]  main
 chunk    {0} bundle.js (main) 0 bytes [entry] [rendered]
     > main [0] (webpack)/test/statsCases/simple-more-info/index.js 
     [0] (webpack)/test/statsCases/simple-more-info/index.js 0 bytes {0} [built]

test/statsCases/simple/expected.txt

@@ -1,6 +1,6 @@
 Hash: 0bd4f09244f0e8c60354
 Time: Xms
     Asset     Size  Chunks             Chunk Names
-bundle.js  2.43 kB       0  [emitted]  main
+bundle.js  2.51 kB       0  [emitted]  main
 chunk    {0} bundle.js (main) 0 bytes [entry] [rendered]
     [0] (webpack)/test/statsCases/simple/index.js 0 bytes {0} [built]

test/statsCases/tree-shaking/expected.txt

@@ -1,7 +1,7 @@
-Hash: 8bac53cc0c37d71baf6b
+Hash: 9e57dbeb6deda98eb9bf
 Time: Xms
     Asset     Size  Chunks             Chunk Names
-bundle.js  7.22 kB       0  [emitted]  main
+bundle.js  7.08 kB       0  [emitted]  main
 chunk    {0} bundle.js (main) 588 bytes [entry] [rendered]
    [0] (webpack)/test/statsCases/tree-shaking/a.js 13 bytes {0} [built]
        [exports: a]
@@ -10,7 +10,7 @@ chunk    {0} bundle.js (main) 588 bytes [entry] [rendered]
        [exports: b]
        [only some exports used: ]
    [2] (webpack)/test/statsCases/tree-shaking/unknown.js 0 bytes {0} [built]
-       [only some exports used: a, c]
+       [only some exports used: c]
    [3] (webpack)/test/statsCases/tree-shaking/edge.js 45 bytes {0} [built]
        [only some exports used: y]
    [4] (webpack)/test/statsCases/tree-shaking/reexport-known.js 49 bytes {0} [built]