From 4305d3717506ab3e8f1a3d25d1cebca2efb7a9dc Mon Sep 17 00:00:00 2001
From: Edward Faulkner <edward@eaf4.com>
Date: Tue, 18 Feb 2025 16:52:47 -0500
Subject: [PATCH] Workaround babel evaluation bug

Fix #2212
Fix #1812
Supersedes #2215

We were already doing most of the evaluation ourselves. Of all the cases we test, the only spot we were relying on babe's `evaluate` was for the undefined keyword, which was easy to add to our own Evaluator.
---
 packages/macros/src/babel/evaluate-json.ts | 15 ++++-----------
 packages/macros/tests/babel/eval.test.ts   |  9 +++++++++
 2 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/packages/macros/src/babel/evaluate-json.ts b/packages/macros/src/babel/evaluate-json.ts
index 9dfdc86aa..84a8cc8c7 100644
--- a/packages/macros/src/babel/evaluate-json.ts
+++ b/packages/macros/src/babel/evaluate-json.ts
@@ -113,12 +113,6 @@ export interface UnknownResult {
 
 export type EvaluateResult = ConfidentResult | UnknownResult;
 
-// this is needed to make our strict types work when inter-operating with
-// babel's own built-in evaluator
-function isConfidentResult(result: { confident: boolean; value: any }): result is ConfidentResult {
-  return result.confident;
-}
-
 export interface EvaluationEnv {
   knownPaths?: Map<NodePath, EvaluateResult>;
   locals?: { [localVar: string]: any };
@@ -193,11 +187,6 @@ export class Evaluator {
   }
 
   private realEvaluate(path: NodePath): EvaluateResult {
-    let builtIn = path.evaluate();
-    if (isConfidentResult(builtIn)) {
-      return { ...builtIn, hasRuntimeImplementation: false };
-    }
-
     if (path.isMemberExpression()) {
       return this.evaluateMember(path, false);
     }
@@ -224,6 +213,10 @@ export class Evaluator {
       return { confident: true, value: null, hasRuntimeImplementation: false };
     }
 
+    if (path.isIdentifier() && path.node.name === 'undefined') {
+      return { confident: true, value: undefined, hasRuntimeImplementation: false };
+    }
+
     if (path.isObjectExpression()) {
       let props = assertArray(path.get('properties')).map(p => {
         if (p.isSpreadElement()) {
diff --git a/packages/macros/tests/babel/eval.test.ts b/packages/macros/tests/babel/eval.test.ts
index 21d35a7ae..9fd6bc7e9 100644
--- a/packages/macros/tests/babel/eval.test.ts
+++ b/packages/macros/tests/babel/eval.test.ts
@@ -116,6 +116,15 @@ describe('evaluation', function () {
         expect(code).toMatch(`a: 1`);
         expect(code).toMatch(`b: unknownValue`);
       });
+
+      test('not subject to https://github.com/babel/babel/issues/14197', () => {
+        let code = transform(`
+          const state = { a: 1 };
+          state.a = 2;
+          const result = state.a;
+        `);
+        expect(code).toMatch('result = state.a');
+      });
     },
   });
 });