make sure calling GetStatus is safe (#164)

hive.go

@@ -358,8 +358,8 @@ func (c *Connection) Close() error {
 	if err != nil {
 		return err
 	}
-	if !success(responseClose.GetStatus()) {
-		return errors.New("Error closing the session: " + responseClose.GetStatus().String())
+	if !success(safeStatus(responseClose.GetStatus())) {
+		return errors.New("Error closing the session: " + safeStatus(responseClose.GetStatus()).String())
 	}
 	return nil
 }
@@ -534,11 +534,11 @@ func (c *Cursor) executeAsync(ctx context.Context, query string) {
 		}
 		return
 	}
-	if !success(responseExecute.GetStatus()) {
+	if !success(safeStatus(responseExecute.GetStatus())) {
 		c.Err = HiveError{
-			error:     errors.New("Error while executing query: " + responseExecute.GetStatus().String()),
-			Message:   *responseExecute.GetStatus().ErrorMessage,
-			ErrorCode: int(*responseExecute.GetStatus().ErrorCode),
+			error:     errors.New("Error while executing query: " + safeStatus(responseExecute.GetStatus()).String()),
+			Message:   *safeStatus(responseExecute.GetStatus()).ErrorMessage,
+			ErrorCode: int(*safeStatus(responseExecute.GetStatus()).ErrorCode),
 		}
 		return
 	}
@@ -562,8 +562,8 @@ func (c *Cursor) Poll(getProgress bool) (status *hiveserver.TGetOperationStatusR
 	if c.Err != nil {
 		return nil
 	}
-	if !success(responsePoll.GetStatus()) {
-		c.Err = errors.New("Error closing the operation: " + responsePoll.GetStatus().String())
+	if !success(safeStatus(responsePoll.GetStatus())) {
+		c.Err = errors.New("Error closing the operation: " + safeStatus(responsePoll.GetStatus()).String())
 		return nil
 	}
 	return responsePoll
@@ -960,7 +960,7 @@ func (c *Cursor) Description() [][]string {
 		return nil
 	}
 	if metaResponse.Status.StatusCode != hiveserver.TStatusCode_SUCCESS_STATUS {
-		c.Err = errors.New(metaResponse.GetStatus().String())
+		c.Err = errors.New(safeStatus(metaResponse.GetStatus()).String())
 		return nil
 	}
 	m := make([][]string, len(metaResponse.Schema.Columns))
@@ -1019,8 +1019,8 @@ func (c *Cursor) pollUntilData(ctx context.Context, n int) (err error) {
 			}
 			c.response = responseFetch
 
-			if responseFetch.GetStatus().StatusCode != hiveserver.TStatusCode_SUCCESS_STATUS {
-				rowsAvailable <- errors.New(responseFetch.GetStatus().String())
+			if safeStatus(responseFetch.GetStatus()).StatusCode != hiveserver.TStatusCode_SUCCESS_STATUS {
+				rowsAvailable <- errors.New(safeStatus(responseFetch.GetStatus()).String())
 				return
 			}
 			err = c.parseResults(responseFetch)
@@ -1071,8 +1071,8 @@ func (c *Cursor) Cancel() {
 	if c.Err != nil {
 		return
 	}
-	if !success(responseCancel.GetStatus()) {
-		c.Err = errors.New("Error closing the operation: " + responseCancel.GetStatus().String())
+	if !success(safeStatus(responseCancel.GetStatus())) {
+		c.Err = errors.New("Error closing the operation: " + safeStatus(responseCancel.GetStatus()).String())
 	}
 	return
 }
@@ -1100,8 +1100,8 @@ func (c *Cursor) resetState() error {
 		if err != nil {
 			return err
 		}
-		if !success(responseClose.GetStatus()) {
-			return errors.New("Error closing the operation: " + responseClose.GetStatus().String())
+		if !success(safeStatus(responseClose.GetStatus())) {
+			return errors.New("Error closing the operation: " + safeStatus(responseClose.GetStatus()).String())
 		}
 		return nil
 	}
@@ -1178,3 +1178,22 @@ func newCookieJar() inMemoryCookieJar {
 	f := false
 	return inMemoryCookieJar{&f, storage}
 }
+
+func safeStatus(status *hiveserver.TStatus) *hiveserver.TStatus {
+	if (status == nil) {
+		return &DEFAULT_STATUS
+	}
+	return status
+}
+
+var DEFAULT_SQL_STATE = ""
+var DEFAULT_ERROR_CODE = int32(-1)
+var DEFAULT_ERROR_MESSAGE = "unknown error"
+var DEFAULT_STATUS = hiveserver.TStatus {
+        StatusCode: 	hiveserver.TStatusCode_ERROR_STATUS,
+        InfoMessages: 	nil,
+        SqlState: 	&DEFAULT_SQL_STATE,
+        ErrorCode: 	&DEFAULT_ERROR_CODE,
+        ErrorMessage: 	&DEFAULT_ERROR_MESSAGE,
+}
+