Added additional builder method receiving arguments for using jsc or hermes to correctly decide which DSO to load at app startup.

ReactAndroid/src/main/java/com/facebook/react/ReactInstanceManagerBuilder.java

@@ -34,6 +34,8 @@
 import com.facebook.react.modules.core.DefaultHardwareBackBtnHandler;
 import com.facebook.react.packagerconnection.RequestHandler;
 import com.facebook.react.uimanager.UIImplementationProvider;
+import com.facebook.react.util.JSInterpreter;
+
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
@@ -66,18 +68,11 @@ public class ReactInstanceManagerBuilder {
  private @Nullable Map<String, RequestHandler> mCustomPackagerCommandHandlers;
  private @Nullable ReactPackageTurboModuleManagerDelegate.Builder mTMMDelegateBuilder;
  private @Nullable SurfaceDelegateFactory mSurfaceDelegateFactory;
- private Boolean hermesEnabled = null;
+ private JSInterpreter jsEngine = JSInterpreter.OLD_LOGIC;
 
  /* package protected Deafault Constructor */
  ReactInstanceManagerBuilder() {}
 
- /**
- * Constructor that takes a Boolean specifying whether to load hermes or jsc
- */
- ReactInstanceManagerBuilder(Boolean hermesEnabled) {
- this.hermesEnabled = hermesEnabled;
- }
-
  /** Sets a provider of {@link UIImplementation}. Uses default provider if null is passed. */
  public ReactInstanceManagerBuilder setUIImplementationProvider(
  @Nullable UIImplementationProvider uiImplementationProvider) {
@@ -134,6 +129,30 @@ public ReactInstanceManagerBuilder setJSBundleLoader(JSBundleLoader jsBundleLoad
  return this;
  }
 
+ /**
+ * Sets the jsEngine as JSC or HERMES as per the setJsEngineAsHermes call
+ * Uses the enum {@link JSInterpreter}
+ * @param jsEngine
+ */
+ private void setJSEngine(JSInterpreter jsEngine){
+ this.jsEngine = jsEngine;
+ }
+
+ /**
+ * Utility setter to set the required JSEngine as HERMES or JSC
+ * Defaults to OLD_LOGIC if not called by the host app
+ * @param hermesEnabled
+ * hermesEnabled = true sets the JS Engine as HERMES and JSC otherwise
+ */
+ public void setJsEngineAsHermes(boolean hermesEnabled){
+ if(hermesEnabled){
+ setJSEngine(JSInterpreter.HERMES);
+ }
+ else{
+ setJSEngine(JSInterpreter.JSC);
+ }
+ }
+
  /**
  * Path to your app's main module on Metro. This is used when reloading JS during development. All
  * paths are relative to the root folder the packager is serving files from. Examples: {@code
@@ -356,15 +375,15 @@ private JavaScriptExecutorFactory getDefaultJSExecutorFactory(
  String appName, String deviceName, Context applicationContext) {
 
  // Relying solely on try catch block and loading jsc even when
- // project is using hermes can lead to launchtime crashes expecially in
+ // project is using hermes can lead to launch-time crashes especially in
  // monorepo architectures and hybrid apps using both native android
  // and react native.
- // So we can use the value of enableHermes receved by the constructor
+ // So we can use the value of enableHermes received by the constructor
  // to decide which library to load at launch
 
  // if nothing is specified, use old loading method
  // else load the required engine
- if (hermesEnabled == null) {
+ if (jsEngine == JSInterpreter.OLD_LOGIC) {
  try {
  // If JSC is included, use it as normal
  initializeSoLoaderIfNecessary(applicationContext);
@@ -377,7 +396,7 @@ private JavaScriptExecutorFactory getDefaultJSExecutorFactory(
  HermesExecutor.loadLibrary();
  return new HermesExecutorFactory();
  }
- } else if (hermesEnabled == true) {
+ } else if (jsEngine == JSInterpreter.HERMES) {
  HermesExecutor.loadLibrary();
  return new HermesExecutorFactory();
  } else {

ReactAndroid/src/main/java/com/facebook/react/util/JSInterpreter.java

@@ -0,0 +1,12 @@
+package com.facebook.react.util;
+
+/**
+ * An enum that specifies the JS Interpreter to be used in the app
+ * Old Logic uses the legacy code
+ * JSC/HERMES loads the respective engine using the revamped logic
+ */
+public enum JSInterpreter {
+ OLD_LOGIC,
+ JSC,
+ HERMES
+}