Use an emit helper for JSX Spread Attributes.

Author: DanielRosenwasser

src/compiler/binder.ts

@@ -122,6 +122,7 @@ namespace ts {
         let hasAsyncFunctions: boolean;
         let hasDecorators: boolean;
         let hasParameterDecorators: boolean;
+        let hasJsxSpreadAttribute: boolean;
 
         // If this file is an external module, then it is automatically in strict-mode according to
         // ES6.  If it is not an external module, then we'll determine if it is in strict mode or
@@ -161,6 +162,7 @@ namespace ts {
             hasAsyncFunctions = false;
             hasDecorators = false;
             hasParameterDecorators = false;
+            hasJsxSpreadAttribute = false;
         }
 
         return bindSourceFile;
@@ -498,6 +500,9 @@ namespace ts {
                 if (hasAsyncFunctions) {
                     flags |= NodeFlags.HasAsyncFunctions;
                 }
+                if (hasJsxSpreadAttribute) {
+                    flags |= NodeFlags.HasJsxSpreadAttribute;
+                }
             }
 
             node.flags = flags;
@@ -1289,6 +1294,10 @@ namespace ts {
                 case SyntaxKind.EnumMember:
                     return bindPropertyOrMethodOrAccessor(<Declaration>node, SymbolFlags.EnumMember, SymbolFlags.EnumMemberExcludes);
 
+                case SyntaxKind.JsxSpreadAttribute:
+                    hasJsxSpreadAttribute = true;
+                    return;
+
                 case SyntaxKind.CallSignature:
                 case SyntaxKind.ConstructSignature:
                 case SyntaxKind.IndexSignature:

src/compiler/emitter.ts

@@ -345,6 +345,15 @@ var __extends = (this && this.__extends) || function (d, b) {
     d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
 };`;
 
+        const assignHelper = `
+var __assign = (this && this.__assign) || Object.assign || function(t) {
+    for (var i = 1, n = arguments.length; i < n; i++) {
+        var s = arguments[i];
+        if (s != null) for (var p in s) if (s.hasOwnProperty(p)) t[p] = s[p];
+    }
+    return t;
+};`;
+
         // emit output for the __decorate helper function
         const decorateHelper = `
 var __decorate = (this && this.__decorate) || function (decorators, target, key, desc) {
@@ -540,6 +549,7 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, ge
             let convertedLoopState: ConvertedLoopState;
 
             let extendsEmitted: boolean;
+            let assignEmitted: boolean;
             let decorateEmitted: boolean;
             let paramEmitted: boolean;
             let awaiterEmitted: boolean;
@@ -623,6 +633,7 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, ge
                 decorateEmitted = false;
                 paramEmitted = false;
                 awaiterEmitted = false;
+                assignEmitted = false;
                 tempFlags = 0;
                 tempVariables = undefined;
                 tempParameters = undefined;
@@ -1259,11 +1270,10 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, ge
                     }
                     else {
                         // Either emit one big object literal (no spread attribs), or
-                        // a call to React.__spread
+                        // a call to the __assign helper
                         const attrs = openingNode.attributes;
                         if (forEach(attrs, attr => attr.kind === SyntaxKind.JsxSpreadAttribute)) {
-                            emitExpressionIdentifier(syntheticReactRef);
-                            write(".__spread(");
+                            write("__assign(");
 
                             let haveOpenedObjectLiteral = false;
                             for (let i = 0; i < attrs.length; i++) {
@@ -7610,11 +7620,16 @@ const _super = (function (geti, seti) {
                 if (!compilerOptions.noEmitHelpers) {
                     // Only Emit __extends function when target ES5.
                     // For target ES6 and above, we can emit classDeclaration as is.
-                    if ((languageVersion < ScriptTarget.ES6) && (!extendsEmitted && node.flags & NodeFlags.HasClassExtends)) {
+                    if (languageVersion < ScriptTarget.ES6 && !extendsEmitted && node.flags & NodeFlags.HasClassExtends) {
                         writeLines(extendsHelper);
                         extendsEmitted = true;
                     }
 
+                    if (compilerOptions.jsx !== JsxEmit.Preserve && !assignEmitted && (node.flags & NodeFlags.HasJsxSpreadAttribute)) {
+                        writeLines(assignHelper);
+                        assignEmitted = true;
+                    }
+
                     if (!decorateEmitted && node.flags & NodeFlags.HasDecorators) {
                         writeLines(decorateHelper);
                         if (compilerOptions.emitDecoratorMetadata) {

src/compiler/types.ts

@@ -369,7 +369,7 @@ namespace ts {
         FirstNode = QualifiedName,
     }
 
-    export const enum NodeFlags {
+    export const enum NodeFlags {
         None =              0,
         Export =            1 << 1,  // Declarations
         Ambient =           1 << 2,  // Declarations
@@ -397,6 +397,10 @@ namespace ts {
         HasParamDecorators =    1 << 24,  // If the file has parameter decorators (initialized by binding)
         HasAsyncFunctions =     1 << 25,  // If the file has async functions (initialized by binding)
 
+        // This was picked out from the 'master' branch.
+        // To keep the flags consistent, we're skipping a few ahead.
+        HasJsxSpreadAttribute = 1 << 30,
+
         Modifier = Export | Ambient | Public | Private | Protected | Static | Abstract | Default | Async,
         AccessibilityModifier = Public | Private | Protected,
         BlockScoped = Let | Const,