From fcfaa05e5c3fdc8284780199fb810245a42cfdd9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nicol=C3=B2=20Ribaudo?= <nicolo.ribaudo@gmail.com>
Date: Sat, 12 Mar 2022 18:31:40 +0100
Subject: [PATCH] [setPublicClassFields] Use define for static `name`/`length`

---
 .../src/fields.ts                             | 27 ++++++++++++++++---
 .../length-name-use-define/input.js           | 11 ++++++++
 .../length-name-use-define/output.js          | 19 +++++++++++++
 3 files changed, 54 insertions(+), 3 deletions(-)
 create mode 100644 packages/babel-plugin-proposal-class-properties/test/fixtures/assumption-setPublicClassFields/length-name-use-define/input.js
 create mode 100644 packages/babel-plugin-proposal-class-properties/test/fixtures/assumption-setPublicClassFields/length-name-use-define/output.js

diff --git a/packages/babel-helper-create-class-features-plugin/src/fields.ts b/packages/babel-helper-create-class-features-plugin/src/fields.ts
index f4083d199f20..16842401fbfb 100644
--- a/packages/babel-helper-create-class-features-plugin/src/fields.ts
+++ b/packages/babel-helper-create-class-features-plugin/src/fields.ts
@@ -936,6 +936,18 @@ export type PropNode =
   | t.StaticBlock;
 export type PropPath = NodePath<PropNode>;
 
+function isNameOrLength(node: t.ClassProperty) {
+  if (node.key.type === "Identifier") {
+    return (
+      !node.computed && (node.key.name === "name" || node.key.name === "length")
+    );
+  }
+  if (node.key.type === "StringLiteral") {
+    return node.key.value === "name" || node.key.value === "length";
+  }
+  return false;
+}
+
 export function buildFieldsInitNodes(
   ref: t.Identifier,
   superRef: t.Expression | undefined,
@@ -1019,10 +1031,19 @@ export function buildFieldsInitNodes(
         );
         break;
       case isStatic && isPublic && isField && setPublicClassFields:
-        needsClassRef = true;
+        // Functions always have non-writable .name and .length properties,
+        // so we must always use [[Define]] for them.
+        // It might still be possible to a computed static fields whose resulting
+        // key is "name" or "length", but the assumption is telling us that it's
+        // not going to happen.
         // @ts-expect-error checked in switch
-        staticNodes.push(buildPublicFieldInitLoose(t.cloneNode(ref), prop));
-        break;
+        if (!isNameOrLength(prop.node)) {
+          needsClassRef = true;
+          // @ts-expect-error checked in switch
+          staticNodes.push(buildPublicFieldInitLoose(t.cloneNode(ref), prop));
+          break;
+        }
+      // falls through
       case isStatic && isPublic && isField && !setPublicClassFields:
         needsClassRef = true;
         staticNodes.push(
diff --git a/packages/babel-plugin-proposal-class-properties/test/fixtures/assumption-setPublicClassFields/length-name-use-define/input.js b/packages/babel-plugin-proposal-class-properties/test/fixtures/assumption-setPublicClassFields/length-name-use-define/input.js
new file mode 100644
index 000000000000..ba1775f8fd16
--- /dev/null
+++ b/packages/babel-plugin-proposal-class-properties/test/fixtures/assumption-setPublicClassFields/length-name-use-define/input.js
@@ -0,0 +1,11 @@
+class A {
+    static name = 1;
+    static length = 2;
+    static foo = 3;
+    static [bar] = 4;
+    static ["name"] = 5;
+    static [name] = 6;
+
+    name = 7;
+    length = 8;
+}
\ No newline at end of file
diff --git a/packages/babel-plugin-proposal-class-properties/test/fixtures/assumption-setPublicClassFields/length-name-use-define/output.js b/packages/babel-plugin-proposal-class-properties/test/fixtures/assumption-setPublicClassFields/length-name-use-define/output.js
new file mode 100644
index 000000000000..27c9b8adfba9
--- /dev/null
+++ b/packages/babel-plugin-proposal-class-properties/test/fixtures/assumption-setPublicClassFields/length-name-use-define/output.js
@@ -0,0 +1,19 @@
+let _bar, _name;
+
+_bar = bar;
+_name = name;
+
+class A {
+  constructor() {
+    this.name = 7;
+    this.length = 8;
+  }
+
+}
+
+babelHelpers.defineProperty(A, "name", 1);
+babelHelpers.defineProperty(A, "length", 2);
+A.foo = 3;
+A[_bar] = 4;
+babelHelpers.defineProperty(A, "name", 5);
+A[_name] = 6;