From 7e0ed3d8b465cf29506f19d4c45ad32a7ec37c81 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nicol=C3=B2=20Ribaudo?= <nicolo.ribaudo@gmail.com>
Date: Mon, 4 Oct 2021 21:09:27 +0200
Subject: [PATCH] Fix perf

---
 packages/babel-parser/src/parser/comments.js  | 55 ++++++++++++-------
 .../babel-parser/src/parser/expression.js     |  8 ++-
 2 files changed, 41 insertions(+), 22 deletions(-)

diff --git a/packages/babel-parser/src/parser/comments.js b/packages/babel-parser/src/parser/comments.js
index 801cfd68672d..c304cf0d1268 100644
--- a/packages/babel-parser/src/parser/comments.js
+++ b/packages/babel-parser/src/parser/comments.js
@@ -27,24 +27,21 @@ export type CommentWhitespace = {
   containingNode: Node | null,
 };
 
+type Comments = Array<Comment>;
+
 /**
- * Merge comments with node's ${type}Comments or assign comments to be
- * ${type}Comments. New comments will be placed before old comments
+ * Merge comments with node's leadingComments or assign comments to be
+ * leadingComments. New comments will be placed before old comments
  * because the commentStack is enumerated reversely.
  *
- * @param {"leading" | "inner" | "trailing"} position
  * @param {Node} node
  * @param {Array<Comment>} comments
  */
-function setComments(
-  position: "leading" | "inner" | "trailing",
-  node: Node,
-  comments: Array<Comment>,
-) {
-  if (node[`${position}Comments`] === undefined) {
-    node[`${position}Comments`] = comments;
+function setLeadingComments(node: Node, comments: Comments) {
+  if (node.leadingComments === undefined) {
+    node.leadingComments = comments;
   } else {
-    node[`${position}Comments`].unshift(...comments);
+    node.leadingComments.unshift(...comments);
   }
 }
 
@@ -56,9 +53,27 @@ function setComments(
  * @param {Node} node
  * @param {Array<Comment>} comments
  */
-export function setInnerComments(node: Node, comments: Array<Comment> | void) {
-  if (comments) {
-    setComments("inner", node, comments);
+export function setInnerComments(node: Node, comments: Comments) {
+  if (node.innerComments === undefined) {
+    node.innerComments = comments;
+  } else {
+    node.innerComments.unshift(...comments);
+  }
+}
+
+/**
+ * Merge comments with node's trailingComments or assign comments to be
+ * trailingComments. New comments will be placed before old comments
+ * because the commentStack is enumerated reversely.
+ *
+ * @param {Node} node
+ * @param {Array<Comment>} comments
+ */
+function setTrailingComments(node: Node, comments: Comments) {
+  if (node.trailingComments === undefined) {
+    node.trailingComments = comments;
+  } else {
+    node.trailingComments.unshift(...comments);
   }
 }
 
@@ -82,9 +97,9 @@ function adjustInnerComments(
     lastElement = elements[--i];
   }
   if (lastElement === null || lastElement.start > commentWS.start) {
-    setComments("inner", node, commentWS.comments);
+    setInnerComments(node, commentWS.comments);
   } else {
-    setComments("trailing", lastElement, commentWS.comments);
+    setTrailingComments(lastElement, commentWS.comments);
   }
 }
 
@@ -150,10 +165,10 @@ export default class CommentsParser extends BaseParser {
     const { comments } = commentWS;
     if (commentWS.leadingNode !== null || commentWS.trailingNode !== null) {
       if (commentWS.leadingNode !== null) {
-        setComments("trailing", commentWS.leadingNode, comments);
+        setTrailingComments(commentWS.leadingNode, comments);
       }
       if (commentWS.trailingNode !== null) {
-        setComments("leading", commentWS.trailingNode, comments);
+        setLeadingComments(commentWS.trailingNode, comments);
       }
     } else {
       /*:: invariant(commentWS.containingNode !== null) */
@@ -190,11 +205,11 @@ export default class CommentsParser extends BaseParser {
             adjustInnerComments(node, node.specifiers, commentWS);
             break;
           default: {
-            setComments("inner", node, comments);
+            setInnerComments(node, comments);
           }
         }
       } else {
-        setComments("inner", node, comments);
+        setInnerComments(node, comments);
       }
     }
   }
diff --git a/packages/babel-parser/src/parser/expression.js b/packages/babel-parser/src/parser/expression.js
index f33316cc5d61..4dcd64a5d6e7 100644
--- a/packages/babel-parser/src/parser/expression.js
+++ b/packages/babel-parser/src/parser/expression.js
@@ -1023,9 +1023,13 @@ export default class ExpressionParser extends LValParser {
       call.extra?.trailingComma,
     );
     // mark inner comments of `async()` as inner comments of `async () =>`
-    setInnerComments(node, call.innerComments);
+    if (call.innerComments) {
+      setInnerComments(node, call.innerComments);
+    }
     // mark trailing comments of `async` to be inner comments
-    setInnerComments(node, call.callee.trailingComments);
+    if (call.callee.trailingComments) {
+      setInnerComments(node, call.callee.trailingComments);
+    }
     return node;
   }