Merge pull request #1000 from jignparm/jignparm/servetag

Make 'serve' tag default again.

tf2onnx/tf_loader.py

@@ -181,8 +181,16 @@ def from_checkpoint(model_path, input_names, output_names):
 def _from_saved_model_v1(sess, model_path, input_names, output_names, tag, signatures):
     """Load tensorflow graph from saved_model."""
 
+    wrn_no_tag = "'--tag' not specified for saved_model. Using --tag serve"
+    wrn_empty_tag = "'--tag' value is empty string. Using tag =[[]]"
+
     if tag is None:
         tag = [tf.saved_model.tag_constants.SERVING]
+        logger.warning(wrn_no_tag)
+
+    if tag == '':
+        tag = [[]]
+        logger.warning(wrn_empty_tag)
 
     if not isinstance(tag, list):
         tag = [tag]
@@ -218,7 +226,8 @@ def _from_saved_model_v1(sess, model_path, input_names, output_names, tag, signa
 def _from_saved_model_v2(model_path, input_names, output_names, tag, signature_def, concrete_function_index):
     """Load tensorflow graph from saved_model."""
 
-    wrn_no_tag = "'--tag' not specified for saved_model. Using empty tag [[]]"
+    wrn_no_tag = "'--tag' not specified for saved_model. Using --tag serve"
+    wrn_empty_tag = "'--tag' value is empty string. Using tag =[[]]"
     wrn_sig_1 = "'--signature_def' not specified, using first signature: %s"
     err_many_sig = "Cannot load multiple signature defs in TF2.x: %s"
     err_no_call = "Model doesn't contain usable concrete functions under  __call__. Try --signature-def instead."
@@ -227,8 +236,13 @@ def _from_saved_model_v2(model_path, input_names, output_names, tag, signature_d
     err_sig_nomatch = "Specified signature not in model %s"
 
     if tag is None:
-        tag = [[]]
+        tag = ['serve']
         logger.warning(wrn_no_tag)
+
+    if tag == '':
+        tag = [[]]
+        logger.warning(wrn_empty_tag)
+
     utils.make_sure(len(signature_def) < 2, err_many_sig, str(signature_def))
     imported = tf.saved_model.load(model_path, tags=tag)  # pylint: disable=no-value-for-parameter