Merge ReactMethod and ReactSyncHook

Reviewed By: astreet

Differential Revision: D4409726

fbshipit-source-id: 7a0091da754b114680772aa9c0a898b1aa721ba5

ReactAndroid/src/main/java/com/facebook/react/bridge/ReactMethod.java

@@ -14,13 +14,28 @@ import java.lang.annotation.Retention;
 import static java.lang.annotation.RetentionPolicy.RUNTIME;
 
 /**
- * Annotation which is used to mark methods that are exposed to
- * Catalyst. This applies to derived classes of {@link
- * BaseJavaModule}, which will generate a list of exported methods by
- * searching for those which are annotated with this annotation and
- * adding a JS callback for each.
+ * Annotation which is used to mark methods that are exposed to React Native.
+ *
+ * This applies to derived classes of {@link BaseJavaModule}, which will generate a list
+ * of exported methods by searching for those which are annotated with this annotation
+ * and adding a JS callback for each.
  */
 @Retention(RUNTIME)
 public @interface ReactMethod {
-
+  /**
+   * Whether the method can be called from JS synchronously **on the JS thread**,
+   * possibly returning a result.
+   *
+   * WARNING: in the vast majority of cases, you should leave this to false which allows
+   * your native module methods to be called asynchronously: calling methods
+   * synchronously can have strong performance penalties and introduce threading-related
+   * bugs to your native modules.
+   *
+   * In order to support remote debugging, both the method args and return type must be
+   * serializable to JSON: this means that we only support the same args as
+   * {@link ReactMethod}, and the hook can only be void or return JSON values (e.g. bool,
+   * number, String, {@link WritableMap}, or {@link WritableArray}). Calling these
+   * methods when running under the websocket executor is currently not supported.
+   */
+  boolean isBlockingSynchronousMethod() default false;
 }