more reliable jsx literal whitespace

lib/6to5/transformation/transformers/jsx.js

@@ -80,10 +80,17 @@ exports.XJSElement = {
     var callExpr = node.openingElement;
     var children = node.children;
 
-    _.each(children, function (child) {
-      if (t.isLiteral(child) && _.isString(child.value)) {
-        child.value = child.value.trim().replace(/\n(\s+)/g, " ");
-        if (!child.value) return;
+    _.each(children, function (child, i) {
+      var val = child.value;
+      if (t.isLiteral(child) && _.isString(val)) {
+        val = val.replace(/\n(\s+)/g, " ");
+
+        i = +i;
+        if (i === 0) val = val.trimLeft();
+        if (i === children.length - 1) val = val.trimRight();
+
+        if (!val) return;
+        child.value = val;
       }
 
       callExpr.arguments.push(child);

test/fixtures/transformation/jsx/everything/expected.js

@@ -3,5 +3,5 @@
 X({
   "data-prop": x ? Y({
     prop: 2
-  }) : Z(null, "\n")
+  }) : Z(null)
 });

test/fixtures/transformation/jsx/tags-with-literals/expected.js

@@ -1,9 +1,9 @@
 "use strict";
 
-(X(null, "   "));
+(X(null));
 
-(X(null, "\n"));
+(X(null));
 
-(X(null, "\n  string\n"));
+(X(null, "string"));
 
-(X(null, "\n  string\n  string\n  "));
+(X(null, "string string"));