Preserve null in babel-types' clone and deepClone. (#4853)

* Preserve null in babel-types' clone and deepClone.
* Also respect undefined when cloning.
* Updating last test to reflect original test case "[,0]"

packages/babel-types/src/index.js

@@ -259,6 +259,7 @@ export function ensureBlock(node: Object, key: string = "body"): Object {
  */
 
 export function clone(node: Object): Object {
+  if (!node) return node;
   let newNode = {};
   for (let key in node) {
     if (key[0] === "_") continue;
@@ -283,6 +284,7 @@ export function cloneWithoutLoc(node: Object): Object {
  */
 
 export function cloneDeep(node: Object): Object {
+  if (!node) return node;
   let newNode = {};
 
   for (let key in node) {

packages/babel-types/test/cloning.js

@@ -0,0 +1,69 @@
+let t = require("../lib");
+let assert = require("assert");
+let parse = require("babylon").parse;
+
+suite("cloning", function () {
+  suite("clone", function () {
+    it("should handle undefined", function () {
+      let node = undefined;
+      let cloned = t.clone(node);
+      assert(cloned === undefined);
+    });
+
+    it("should handle null", function () {
+      let node = null;
+      let cloned = t.clone(node);
+      assert(cloned === null);
+    });
+
+    it("should handle simple cases", function () {
+      let node = t.arrayExpression([null, t.identifier("a")]);
+      let cloned = t.clone(node);
+      assert(node !== cloned);
+      assert(t.isNodesEquivalent(node, cloned) === true);
+    });
+  });
+
+  suite("cloneDeep", function () {
+    it("should handle undefined", function () {
+      let node = undefined;
+      let cloned = t.cloneDeep(node);
+      assert(cloned === undefined);
+    });
+
+    it("should handle null", function () {
+      let node = null;
+      let cloned = t.cloneDeep(node);
+      assert(cloned === null);
+    });
+
+    it("should handle simple cases", function () {
+      let node = t.arrayExpression([null, t.identifier("a")]);
+      let cloned = t.cloneDeep(node);
+      assert(node !== cloned);
+      assert(t.isNodesEquivalent(node, cloned) === true);
+    });
+
+    it("should handle full programs", function () {
+      let node = parse("1 + 1");
+      let cloned = t.cloneDeep(node);
+      assert(node !== cloned);
+      assert(t.isNodesEquivalent(node, cloned) === true);
+    });
+
+    it("should handle complex programs", function () {
+      let program = "'use strict'; function lol() { wow();return 1; }";
+      let node = parse(program);
+      let cloned = t.cloneDeep(node);
+      assert(node !== cloned);
+      assert(t.isNodesEquivalent(node, cloned) === true);
+    });
+
+    it("should handle missing array element", function () {
+      let node = parse("[,0]");
+      let cloned = t.cloneDeep(node);
+      assert(node !== cloned);
+      assert(t.isNodesEquivalent(node, cloned) === true);
+    });
+  });
+});