refactor: make status extraction transport-neutral

Rename extractGrpcStatusCode to extractStatusCode and remove the
io.grpc.Status dependency. The reason string on DatastoreException is
already set from GAX's StatusCode.Code which supports both gRPC and
HttpJson transports. Use a plain "UNKNOWN" string as fallback.

Author: lqiu96

java-datastore/google-cloud-datastore/src/main/java/com/google/cloud/datastore/DatastoreException.java

@@ -162,15 +162,16 @@ static DatastoreException propagateUserException(Exception ex) {
   }
 
   /**
-   * Extracts the gRPC status code name from the given throwable. Walks the exception cause chain
-   * looking for a {@link DatastoreException} that carries a gRPC reason string (e.g. "ABORTED",
-   * "UNAVAILABLE"). Falls back to {@link io.grpc.Status.Code#UNKNOWN} if the status cannot be
-   * determined.
+   * Extracts the status code name from the given throwable. Walks the exception cause chain looking
+   * for a {@link DatastoreException} that carries a reason string representing the status code
+   * (e.g. "ABORTED", "UNAVAILABLE"). The reason is set from {@link
+   * com.google.api.gax.rpc.StatusCode.Code} which is transport-neutral, supporting both gRPC and
+   * HttpJson. Falls back to "UNKNOWN" if the status cannot be determined.
    *
-   * @param throwable the throwable to extract the gRPC status code from
-   * @return the gRPC status code name, or "UNKNOWN" if not determinable
+   * @param throwable the throwable to extract the status code from
+   * @return the status code name, or "UNKNOWN" if not determinable
    */
-  static String extractGrpcStatusCode(Throwable throwable) {
+  static String extractStatusCode(Throwable throwable) {
     Throwable current = throwable;
     while (current != null) {
       if (current instanceof DatastoreException) {
@@ -181,6 +182,6 @@ static String extractGrpcStatusCode(Throwable throwable) {
       }
       current = current.getCause();
     }
-    return io.grpc.Status.Code.UNKNOWN.toString();
+    return "UNKNOWN";
   }
 }

java-datastore/google-cloud-datastore/src/main/java/com/google/cloud/datastore/DatastoreImpl.java

@@ -220,7 +220,7 @@ public T call() throws DatastoreException {
         return value;
       } catch (Exception ex) {
         transaction.rollback();
-        recordAttempt(DatastoreException.extractGrpcStatusCode(ex));
+        recordAttempt(DatastoreException.extractStatusCode(ex));
         throw DatastoreException.propagateUserException(ex);
       } finally {
         if (transaction.isActive()) {
@@ -287,7 +287,7 @@ public <T> T runInTransaction(
           TRANSACTION_EXCEPTION_HANDLER,
           getOptions().getClock());
     } catch (RetryHelperException e) {
-      status = extractGrpcStatusCode(e);
+      status = DatastoreException.extractStatusCode(e);
       span.end(e);
       throw DatastoreException.translateAndThrow(e);
     } finally {
@@ -302,21 +302,6 @@ public <T> T runInTransaction(
     }
   }
 
-  /**
-   * Extracts the gRPC status code from a {@link RetryHelperException}. The underlying cause is
-   * expected to be a {@link DatastoreException} which carries the gRPC reason. Falls back to
-   * "UNKNOWN" if the status cannot be determined.
-   */
-  private static String extractGrpcStatusCode(RetryHelperException e) {
-    Throwable cause = e.getCause();
-    if (cause instanceof DatastoreException) {
-      String reason = ((DatastoreException) cause).getReason();
-      if (reason != null && !reason.isEmpty()) {
-        return reason;
-      }
-    }
-    return "UNKNOWN";
-  }
 
   @Override
   public <T> QueryResults<T> run(Query<T> query) {