Revert D89724839: Disable JS class transforms for Hermes V1 (use SH-native class support)

Differential Revision:
D89724839

Original commit changeset: c25d0080ddac

Original Phabricator Diff: D89724839

fbshipit-source-id: af32de790f3f591826a57352d90629ce278ab14d

Author: robhogan

packages/react-native-babel-preset/src/configs/main.js

@@ -20,6 +20,10 @@ const EXCLUDED_FIRST_PARTY_PATHS = [
   /[/\\]private[/\\]react-native-fantom[/\\]/,
 ];
 
+// customTransformOptions may be strings from URL params, or booleans passed
+// programatically. For strings, handle them as Metro does when parsing URLs.
+const TRUE_VALS = new Set([true, 'true', '1']);
+
 function isTypeScriptSource(fileName) {
   return !!fileName && fileName.endsWith('.ts');
 }
@@ -50,28 +54,25 @@ const getPreset = (src, options, babel) => {
   const transformProfile =
     options?.unstable_transformProfile ?? babel?.caller(getTransformProfile);
 
-  // Hermes V1 (aka Static Hermes) uses more optimised profiles.
-  // There is currently no difference between stable and canary, but canary
-  // may in future be used to test features in pre-prod Hermes versions.
-  const isHermesV1 =
-    transformProfile === 'hermes-stable' ||
-    transformProfile === 'hermes-canary';
+  const isHermesStable = transformProfile === 'hermes-stable';
+  const isHermesCanary = transformProfile === 'hermes-canary';
+  const isHermes = isHermesStable || isHermesCanary;
 
   // We enable regenerator in dev builds for the time being because
-  // Hermes V1 doesn't yet fully support debugging native generators.
+  // Static Hermes doesn't yet fully support debugging native generators.
   // (e.g. - it's not possible to inspect local variables when paused in a
   // generator).
   //
   // Use native generators in release mode because it has already yielded perf
-  // wins. The next release of Hermes will close this gap, so this won't
+  // wins. The next release of Static Hermes will close this gap, so this won't
   // be permanent.
-  const enableRegenerator = isHermesV1 && options.dev;
-
-  // Preserve class syntax and related if we're using Hermes V1.
-  const preserveClasses = isHermesV1;
+  const enableRegenerator = isHermes && options.dev;
 
   const isNull = src == null;
   const hasClass = isNull || src.indexOf('class') !== -1;
+  const preserveClasses = TRUE_VALS.has(
+    options?.customTransformOptions?.unstable_preserveClasses,
+  );
 
   const extraPlugins = [];
   const firstPartyPlugins = [];