Add support for JSXSpreadChild and fix comments inside JSXSpread (#3163)

* Add support for JSXSpreadChild and fix comments inside JSXSpread

* Dangling comments

* Use another approach

src/printer.js

@@ -1716,7 +1716,28 @@ function genericPrintNoParens(path, options, print, args) {
     case "TSQualifiedName":
       return join(".", [path.call(print, "left"), path.call(print, "right")]);
     case "JSXSpreadAttribute":
-      return concat(["{...", path.call(print, "argument"), "}"]);
+    case "JSXSpreadChild": {
+      return concat([
+        "{",
+        path.call(p => {
+          const printed = concat(["...", print(p)]);
+          const n = p.getValue();
+          if (!n.comments || !n.comments.length) {
+            return printed;
+          }
+          return concat([
+            indent(
+              concat([
+                softline,
+                comments.printComments(p, () => printed, options)
+              ])
+            ),
+            softline
+          ]);
+        }, n.type === "JSXSpreadAttribute" ? "argument" : "expression"),
+        "}"
+      ]);
+    }
     case "JSXExpressionContainer": {
       const parent = path.getParentNode(0);
 
@@ -4973,7 +4994,9 @@ function printAstToDoc(ast, options, addAlignmentSize) {
     if (
       ((node && node.type === "JSXElement") ||
         (parent &&
-          (parent.type === "UnionTypeAnnotation" ||
+          (parent.type === "JSXSpreadAttribute" ||
+            parent.type === "JSXSpreadChild" ||
+            parent.type === "UnionTypeAnnotation" ||
             parent.type === "TSUnionType" ||
             ((parent.type === "ClassDeclaration" ||
               parent.type === "ClassExpression") &&

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

@@ -0,0 +1,117 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`attribute.js 1`] = `
+<div {...a}/>;
+
+<div {...a /* comment */}/>;
+
+<div {/* comment */...a}/>;
+
+<div {...a //comment
+}/>;
+
+<div {...a
+  //comment
+}/>;
+
+<div {
+  //comment
+  ...a
+}/>;
+
+<div {//comment
+  ...a // comment
+}/>;
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+<div {...a} />;
+
+<div {...a /* comment */} />;
+
+<div {/* comment */ ...a} />;
+
+<div
+  {
+    ...a //comment
+  }
+/>;
+
+<div
+  {
+    ...a
+    //comment
+  }
+/>;
+
+<div
+  {
+    //comment
+    ...a
+  }
+/>;
+
+<div
+  {
+    //comment
+    ...a // comment
+  }
+/>;
+
+`;
+
+exports[`child.js 1`] = `
+<div>{...a}</div>;
+
+<div>{...a /* comment */}</div>;
+
+<div>{/* comment */...a}</div>;
+
+<div>{...a //comment
+}</div>;
+
+<div>{...a
+  //comment
+}</div>;
+
+<div>{
+  //comment
+  ...a
+}</div>;
+
+<div>{//comment
+  ...a // comment
+}</div>;
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+<div>{...a}</div>;
+
+<div>{...a /* comment */}</div>;
+
+<div>{/* comment */ ...a}</div>;
+
+<div>
+  {
+    ...a //comment
+  }
+</div>;
+
+<div>
+  {
+    ...a
+    //comment
+  }
+</div>;
+
+<div>
+  {
+    //comment
+    ...a
+  }
+</div>;
+
+<div>
+  {
+    //comment
+    ...a // comment
+  }
+</div>;
+
+`;

tests/jsx_spread/attribute.js

@@ -0,0 +1,21 @@
+<div {...a}/>;
+
+<div {...a /* comment */}/>;
+
+<div {/* comment */...a}/>;
+
+<div {...a //comment
+}/>;
+
+<div {...a
+  //comment
+}/>;
+
+<div {
+  //comment
+  ...a
+}/>;
+
+<div {//comment
+  ...a // comment
+}/>;

tests/jsx_spread/child.js

@@ -0,0 +1,21 @@
+<div>{...a}</div>;
+
+<div>{...a /* comment */}</div>;
+
+<div>{/* comment */...a}</div>;
+
+<div>{...a //comment
+}</div>;
+
+<div>{...a
+  //comment
+}</div>;
+
+<div>{
+  //comment
+  ...a
+}</div>;
+
+<div>{//comment
+  ...a // comment
+}</div>;

tests/jsx_spread/jsfmt.spec.js

@@ -0,0 +1 @@
+run_spec(__dirname, { parser: "babylon" });