Merge branch 'master' of github.com:babel/babel

src/babel/transformation/modules/system.js

@@ -78,6 +78,7 @@ export default class SystemFormatter extends AMDFormatter {
   constructor(file) {
     super(file);
 
+    this._setters = null;
     this.exportIdentifier = file.scope.generateUidIdentifier("export");
     this.noInteropRequireExport = true;
     this.noInteropRequireImport = true;
@@ -178,11 +179,14 @@ export default class SystemFormatter extends AMDFormatter {
 
     var block = t.blockStatement(program.body);
 
+    var setterListNode = this._buildRunnerSetters(block, hoistDeclarators);
+    this._setters = setterListNode;
+
     var runner = util.template("system", {
       MODULE_DEPENDENCIES: t.arrayExpression(this.buildDependencyLiterals()),
       EXPORT_IDENTIFIER:   this.exportIdentifier,
       MODULE_NAME:         moduleNameLiteral,
-      SETTERS:             this._buildRunnerSetters(block, hoistDeclarators),
+      SETTERS:             setterListNode,
       EXECUTE:             t.functionExpression(null, [], block)
     }, true);
 

src/babel/transformation/transformers/es6/destructuring.js

@@ -316,9 +316,12 @@ class DestructuringTransformer {
 
     var left = pattern.left;
     if (t.isPattern(left)) {
-      this.nodes.push(t.expressionStatement(
+      var tempValueDefault = t.expressionStatement(
         t.assignmentExpression("=", tempValueRef, tempConditional)
-      ));
+      );
+      tempValueDefault._blockHoist = this.blockHoist;
+
+      this.nodes.push(tempValueDefault);
       this.push(left, tempValueRef);
     } else {
       this.nodes.push(this.buildVariableAssignment(left, tempConditional));

src/babel/transformation/transformers/index.js

@@ -84,4 +84,5 @@ export default {
   _blockHoist:                             require("./internal/block-hoist"),
   jscript:                                 require("babel-plugin-jscript"),
   flow:                                    require("./other/flow"),
+  "optimisation.modules.system":           require("./optimisation/modules.system"),
 };

src/babel/transformation/transformers/optimisation/modules.system.js

@@ -0,0 +1,50 @@
+import * as t from "../../../types";
+
+export var metadata = {
+  optional: true,
+  group: "builtin-trailing"
+};
+
+export var visitor = {
+  Program(node, parent, scope, file){
+    if (file.moduleFormatter._setters){
+      scope.traverse(file.moduleFormatter._setters, optimizeSettersVisitor, {
+        exportFunctionIdentifier: file.moduleFormatter.exportIdentifier
+      });
+    }
+  }
+};
+
+/**
+ * Setters are optimized to avoid slow export behavior in modules that rely on deep hierarchies
+ * of export-from declarations.
+ * More info in https://github.com/babel/babel/pull/1722 and
+ * https://github.com/ModuleLoader/es6-module-loader/issues/386.
+ *
+ * TODO: Ideally this would be optimized during construction of the setters, but the current
+ * architecture of the module formatters make that difficult.
+ */
+var optimizeSettersVisitor = {
+  FunctionExpression: {
+    enter: (node, parent, scope, state) => {
+      state.hasExports = false;
+      state.exportObjectIdentifier = scope.generateUidIdentifier("exportObj");
+    },
+    exit: (node, parent, scope, state) => {
+      if (!state.hasExports) return;
+
+      node.body.body.unshift(t.variableDeclaration("var", [
+        t.variableDeclarator(t.cloneDeep(state.exportObjectIdentifier), t.objectExpression([]))
+      ]));
+      node.body.body.push(t.expressionStatement(t.callExpression(
+        t.cloneDeep(state.exportFunctionIdentifier), [t.cloneDeep(state.exportObjectIdentifier)])));
+    }
+  },
+  CallExpression: (node, parent, scope, state) => {
+    if (!t.isIdentifier(node.callee, {name: state.exportFunctionIdentifier.name})) return;
+
+    state.hasExports = true;
+    var memberNode = t.memberExpression(t.cloneDeep(state.exportObjectIdentifier), node.arguments[0], true);
+    return t.assignmentExpression("=", memberNode, node.arguments[1]);
+  }
+};