make #683 more inline with the official jsx compiler

lib/6to5/transformation/transformers/other/react.js

@@ -5,8 +5,8 @@
 
 // jsx
 
-var esutils  = require("esutils");
 var isString = require("lodash/lang/isString");
+var esutils  = require("esutils");
 var react    = require("../../helpers/react");
 var t        = require("../../../types");
 
@@ -161,6 +161,8 @@ exports.JSXElement = {
       callExpr.arguments.push(child);
     }
 
+    callExpr.arguments = flatten(callExpr.arguments);
+
     if (callExpr.arguments.length >= 3) {
       callExpr._prettyCall = true;
     }
@@ -169,6 +171,27 @@ exports.JSXElement = {
   }
 };
 
+var isStringLiteral = function (node) {
+  return t.isLiteral(node) && isString(node.value);
+};
+
+var flatten = function (args) {
+  var flattened = [];
+  var last;
+
+  for (var i = 0; i < args.length; i++) {
+    var arg = args[i];
+    if (isStringLiteral(arg) && isStringLiteral(last)) {
+      last.value += arg.value;
+    } else {
+      last = arg;
+      flattened.push(arg);
+    }
+  }
+
+  return flattened;
+};
+
 var cleanJSXElementLiteralChild = function (child, args) {
   var lines = child.value.split(/\r\n|\n|\r/);
 
@@ -186,6 +209,7 @@ var cleanJSXElementLiteralChild = function (child, args) {
 
     var isFirstLine = i === 0;
     var isLastLine = i === lines.length - 1;
+    var isLastNonEmptyLine = i === lastNonEmptyLine;
 
     // replace rendered whitespace tabs with spaces
     var trimmedLine = line.replace(/\t/g, " ");
@@ -201,12 +225,11 @@ var cleanJSXElementLiteralChild = function (child, args) {
     }
 
     if (trimmedLine) {
-      var lastArg = args[args.length - 1];
-      if (t.isLiteral(lastArg) && isString(lastArg.value)) {
-        lastArg.value += " " + trimmedLine;
-      } else {
-        args.push(t.literal(trimmedLine));
+      if (!isLastNonEmptyLine) {
+        trimmedLine += " ";
       }
+
+      args.push(t.literal(trimmedLine));
     }
   }
 };