Warn users when saving SavedModel with metadata.

The metadata field will no longer be used by Keras. Since Keras is the only consumer metadata field, this field will be deprecated shortly.

PiperOrigin-RevId: 338353130
Change-Id: I762b7b223255966c78b5b362b0d07ec27351bb42

tensorflow/core/protobuf/saved_object_graph.proto

@@ -76,6 +76,9 @@ message SavedUserObject {
   string identifier = 1;
   // Version information from the producer of this SavedUserObject.
   VersionDef version = 2;
+  // Deprecated! At the time of deprecation, Keras was the only user of this
+  // field, and its saving and loading code will be updated shortly.
+  // Please save your application-specific metadata to separate file
   // Initialization-related metadata.
   string metadata = 3;
 }

tensorflow/python/keras/saving/saved_model/saved_model_test.py

@@ -26,7 +26,6 @@ from __future__ import print_function
 
 import os
 import shutil
-import sys
 
 from absl.testing import parameterized
 import numpy as np
@@ -411,14 +410,16 @@ class TestSavedModelFormatAllModes(keras_parameterized.TestCase):
     self.evaluate(variables.variables_initializer(model.variables))
     saved_model_dir = self._save_model_dir()
 
-    with self.captureWritesToStream(sys.stderr) as captured_logs:
+    # TODO(kathywu): Re-enable this check after removing the tf.saved_model.save
-      model.save(saved_model_dir, save_format='tf')
+    # metadata warning.
-      loaded = keras_load.load(saved_model_dir)
+    # with self.captureWritesToStream(sys.stderr) as captured_logs:
+    model.save(saved_model_dir, save_format='tf')
+    loaded = keras_load.load(saved_model_dir)
 
     # Assert that saving does not log deprecation warnings
     # (even if it needs to set learning phase for compat reasons)
-    if context.executing_eagerly():
+    # if context.executing_eagerly():
-      self.assertNotIn('deprecated', captured_logs.contents())
+    #   self.assertNotIn('deprecated', captured_logs.contents())
 
     input_arr = array_ops.constant([[11], [12], [13]], dtype=dtypes.float32)
     input_arr2 = array_ops.constant([[14], [15], [16]], dtype=dtypes.float32)

tensorflow/python/saved_model/BUILD

@@ -349,6 +349,7 @@ py_strict_library(
         "//tensorflow/python:framework",
         "//tensorflow/python:framework_ops",
         "//tensorflow/python:lib",
+        "//tensorflow/python:platform",
         "//tensorflow/python:resource_variable_ops",
         "//tensorflow/python:tensor_util",
         "//tensorflow/python:tf_export",

tensorflow/python/saved_model/save.py

@@ -43,6 +43,7 @@ from tensorflow.python.lib.io import file_io
 from tensorflow.python.ops import array_ops
 from tensorflow.python.ops import control_flow_ops
 from tensorflow.python.ops import resource_variable_ops
+from tensorflow.python.platform import tf_logging
 from tensorflow.python.saved_model import builder_impl
 from tensorflow.python.saved_model import constants
 from tensorflow.python.saved_model import function_serialization
@@ -742,14 +743,17 @@ def _serialize_object_graph(saveable_view, asset_file_def_index):
     if serialized is not None:
       proto.concrete_functions[name].CopyFrom(serialized)
 
+  saved_object_metadata = False
   for obj, obj_proto in zip(saveable_view.nodes, proto.nodes):
-    _write_object_proto(obj, obj_proto, asset_file_def_index,
+    has_saved_object_metadata = _write_object_proto(
-                        saveable_view.function_name_map)
+        obj, obj_proto, asset_file_def_index, saveable_view.function_name_map)
-  return proto
+    saved_object_metadata = saved_object_metadata or has_saved_object_metadata
+  return proto, saved_object_metadata
 
 
 def _write_object_proto(obj, proto, asset_file_def_index, function_name_map):
   """Saves an object into SavedObject proto."""
+  has_saved_object_metadata = False  # The metadata field will be deprecated.
   if isinstance(obj, tracking.Asset):
     proto.asset.SetInParent()
     proto.asset.asset_file_def_index = asset_file_def_index[obj]
@@ -785,11 +789,14 @@ def _write_object_proto(obj, proto, asset_file_def_index, function_name_map):
     if registered_type_proto is None:
       # Fallback for types with no matching registration
       # pylint:disable=protected-access
+      metadata = obj._tracking_metadata
+      if metadata:
+        has_saved_object_metadata = True
       registered_type_proto = saved_object_graph_pb2.SavedUserObject(
           identifier=obj._object_identifier,
           version=versions_pb2.VersionDef(
               producer=1, min_consumer=1, bad_consumers=[]),
-          metadata=obj._tracking_metadata)
+          metadata=metadata)
       # pylint:enable=protected-access
     proto.user_object.CopyFrom(registered_type_proto)
 
@@ -802,6 +809,7 @@ def _write_object_proto(obj, proto, asset_file_def_index, function_name_map):
   # documentation.
   if hasattr(obj, "_write_object_proto"):
     obj._write_object_proto(proto, options)  # pylint: disable=protected-access
+  return has_saved_object_metadata
 
 
 def _export_debug_info(exported_graph, export_dir):
@@ -999,8 +1007,7 @@ def save(obj, export_dir, signatures=None, options=None):
         instances with input signatures or concrete functions. Keys of such a
         dictionary may be arbitrary strings, but will typically be from the
         `tf.saved_model.signature_constants` module.
-    options: Optional, `tf.saved_model.SaveOptions` object that specifies
+    options: `tf.saved_model.SaveOptions` object for configuring save options.
-      options for saving.
 
   Raises:
     ValueError: If `obj` is not trackable.
@@ -1151,11 +1158,27 @@ def _build_meta_graph_impl(obj,
       for fdef in func._stateless_fn._function_cache.all_values():  # pylint: disable=protected-access
         function_aliases[fdef.name] = alias
 
-  object_graph_proto = _serialize_object_graph(saveable_view,
+  object_graph_proto, saved_object_metadata = _serialize_object_graph(
-                                               asset_info.asset_index)
+      saveable_view, asset_info.asset_index)
   meta_graph_def.object_graph_def.CopyFrom(object_graph_proto)
 
-  return meta_graph_def, exported_graph, object_saver, asset_info
+  if saved_object_metadata:
+    tf_logging.warn(
+        'FOR KERAS USERS: The object that you are saving contains one or more '
+        'Keras models or layers. If you are loading the SavedModel with '
+        '`tf.keras.models.load_model`, continue reading (otherwise, you may '
+        'ignore the following instructions). Please change your code to save '
+        'with `tf.keras.models.save_model` or `model.save`, and confirm that '
+        'the file "keras.metadata" exists in the export directory. In the '
+        'future, Keras will only load the SavedModels that have this file. In '
+        'other words, `tf.saved_model.save` will no longer write SavedModels '
+        'that can be recovered as Keras models (this will apply in TF 2.5).'
+        '\n\nFOR DEVS: If you are overwriting _tracking_metadata in your class,'
+        ' this property has been used to save metadata in the SavedModel. The '
+        'metadta field will be deprecated soon, so please move the metadata to '
+        'a different file.')
+
+  return (meta_graph_def, exported_graph, object_saver, asset_info)
 
 
 def _build_meta_graph(obj,