From bd4590e546faab5238b95a41ffc8bef995e16352 Mon Sep 17 00:00:00 2001
From: Chris West <solo-github@goeswhere.com>
Date: Wed, 13 Jan 2021 01:40:23 +0000
Subject: [PATCH] fix: cloneNode(deep, withoutLoc) handles absent comments
 (#12602)

This fragment (maybe all fragments?) throw during cloning, as
'comments' is unset here. Handle it being unset, by returning
undefined.
---
 packages/babel-types/src/clone/cloneNode.ts | 14 +++++++++++---
 packages/babel-types/test/cloning.js        |  8 ++++++++
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/packages/babel-types/src/clone/cloneNode.ts b/packages/babel-types/src/clone/cloneNode.ts
index 1ef270afe2..826d54c53e 100644
--- a/packages/babel-types/src/clone/cloneNode.ts
+++ b/packages/babel-types/src/clone/cloneNode.ts
@@ -102,7 +102,9 @@ export default function cloneNode<T extends t.Node>(
   return newNode;
 }
 
-function cloneCommentsWithoutLoc<T extends t.Comment>(comments: T[]): T[] {
+function cloneCommentsWithoutLoc<T extends t.Comment>(
+  comments: ReadonlyArray<T>,
+): T[] {
   return comments.map(
     ({ type, value }) =>
       ({
@@ -113,6 +115,12 @@ function cloneCommentsWithoutLoc<T extends t.Comment>(comments: T[]): T[] {
   );
 }
 
-function maybeCloneComments(comments, deep, withoutLoc) {
-  return deep && withoutLoc ? cloneCommentsWithoutLoc(comments) : comments;
+function maybeCloneComments<T extends t.Comment>(
+  comments: ReadonlyArray<T> | null,
+  deep: boolean,
+  withoutLoc: boolean,
+): ReadonlyArray<T> | null {
+  return deep && withoutLoc && comments
+    ? cloneCommentsWithoutLoc(comments)
+    : comments;
 }
diff --git a/packages/babel-types/test/cloning.js b/packages/babel-types/test/cloning.js
index c8c3955157..6cbb1cfe05 100644
--- a/packages/babel-types/test/cloning.js
+++ b/packages/babel-types/test/cloning.js
@@ -42,6 +42,14 @@ describe("cloneNode", function () {
     expect(t.isNodesEquivalent(node, cloned)).toBe(true);
   });
 
+  it("should handle deep cloning without loc of fragments", function () {
+    const program = "foo();";
+    const node = parse(program);
+    const cloned = t.cloneNode(node, /* deep */ true, /* withoutLoc */ true);
+    expect(node).not.toBe(cloned);
+    expect(t.isNodesEquivalent(node, cloned)).toBe(true);
+  });
+
   it("should handle missing array element", function () {
     const node = parse("[,0]");
     const cloned = t.cloneNode(node);