Fix single indented JSX comment (#596)

This one was pretty annoying to figure out but now it's working. All the crazy comments I could throw at jsx seems to be working fine now :)

Fixes #543

src/printer.js

@@ -1131,12 +1131,13 @@ function genericPrintNoParens(path, options, print) {
         n.expression.type === "ArrowFunctionExpression" ||
         n.expression.type === "CallExpression" ||
         n.expression.type === "FunctionExpression" ||
+        n.expression.type === "JSXEmptyExpression" ||
         parent.type === "JSXElement" &&
           (n.expression.type === "ConditionalExpression" ||
             n.expression.type === "LogicalExpression");
 
       if (shouldInline) {
-        return concat(["{", path.call(print, "expression"), "}"]);
+        return group(concat(["{", path.call(print, "expression"), "}"]));
       }
 
       return group(
@@ -1198,7 +1199,7 @@ function genericPrintNoParens(path, options, print) {
     case "JSXText":
       throw new Error("JSXTest should be handled by JSXElement");
     case "JSXEmptyExpression":
-      return comments.printDanglingComments(path, options);
+      return concat([comments.printDanglingComments(path, options), softline]);
     case "TypeAnnotatedIdentifier":
       return concat([
         path.call(print, "annotation"),

tests/comments/__snapshots__/jsfmt.spec.js.snap

@@ -640,6 +640,12 @@ foo(
 
 exports[`test jsx.js 1`] = `
 "<div>
+  {
+    /* comment */
+  }
+</div>;
+
+<div>
   {/* comment */
   }
 </div>;
@@ -672,6 +678,12 @@ exports[`test jsx.js 1`] = `
   {/* comment */}
 </div>;
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+<div>
+  {
+    /* comment */
+  }
+</div>;
+
 <div>
   {/* comment */}
 </div>;
@@ -706,6 +718,12 @@ exports[`test jsx.js 1`] = `
 
 exports[`test jsx.js 2`] = `
 "<div>
+  {
+    /* comment */
+  }
+</div>;
+
+<div>
   {/* comment */
   }
 </div>;
@@ -738,6 +756,12 @@ exports[`test jsx.js 2`] = `
   {/* comment */}
 </div>;
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+<div>
+  {
+    /* comment */
+  }
+</div>;
+
 <div>
   {/* comment */}
 </div>;

tests/comments/jsx.js

@@ -1,3 +1,9 @@
+<div>
+  {
+    /* comment */
+  }
+</div>;
+
 <div>
   {/* comment */
   }