[compiler][patch] Emit unary expressions instead of negative numbers

mofeiZ · mofeiZ · commit 7bb66f220ffe · 2025-05-30T11:59:02.000-04:00
This is a babel bug + edge case. Babel compact mode produces invalid JavaScript (i.e. parse error) when given a `NumericLiteral` with a negative value. See https://codesandbox.io/p/devbox/5d47fr for repro. As a followup, we could change our test infra parse babel options (e.g. a babel transform options pragma) which could let us track regressions. We may add an "exhaustive" mode to the compiler test runner to test (1) different babel options and (2) commonly used versions.
diff --git a/compiler/packages/babel-plugin-react-compiler/src/ReactiveScopes/CodegenReactiveFunction.ts b/compiler/packages/babel-plugin-react-compiler/src/ReactiveScopes/CodegenReactiveFunction.ts
@@ -1726,7 +1726,7 @@ function codegenInstructionValue(
     }
     case 'UnaryExpression': {
       value = t.unaryExpression(
-        instrValue.operator as 'throw', // todo
+        instrValue.operator,
         codegenPlaceToExpression(cx, instrValue.value),
       );
       break;
@@ -2582,7 +2582,13 @@ function codegenValue(
   value: boolean | number | string | null | undefined,
 ): t.Expression {
   if (typeof value === 'number') {
-    return t.numericLiteral(value);
+    if (value < 0) {
+      // Babel compact mode produces invalid JS for negative numbers
+      // See https://codesandbox.io/p/devbox/5d47fr
+      return t.unaryExpression('-', t.numericLiteral(-value), false);
+    } else {
+      return t.numericLiteral(value);
+    }
   } else if (typeof value === 'boolean') {
     return t.booleanLiteral(value);
   } else if (typeof value === 'string') {
