[2.8 backport] Resolve bug with re-saving Estimator-exported SavedModel

tensorflow/python/saved_model/load_v1_in_v2.py

@@ -138,7 +138,7 @@ def _extract_signatures(self, wrapped, meta_graph_def):
     for signature_key, signature_def in meta_graph_def.signature_def.items():
       if signature_def.inputs:
         input_items = sorted(
-            signature_def.inputs.items(), key=lambda item: item[1].name)
+            signature_def.inputs.items(), key=lambda item: item[0])
         original_input_names, input_specs = zip(*input_items)
       else:
         original_input_names = []

tensorflow/python/saved_model/load_v1_in_v2_test.py

@@ -692,6 +692,33 @@ def test_v1_input_ordered(self):
     self.assertEqual(imported.signatures["serving_default"].inputs[1].name,
                      "input2:0")
 
+  def test_resave_signature(self):
+    # Tests that signatures saved using TF1 can be resaved with TF2.
+    # See b/211666001 for context.
+    export_graph = ops.Graph()
+    with export_graph.as_default():
+      a = array_ops.placeholder(
+          shape=[None, 1], dtype=dtypes.float32, name="input_2")
+      b = array_ops.placeholder(
+          shape=[None, 2], dtype=dtypes.float32, name="input_1")
+      c = array_ops.identity(a)
+      with session_lib.Session() as session:
+        path = os.path.join(self.get_temp_dir(), "saved_model", str(ops.uid()))
+        simple_save.simple_save(
+            session,
+            path,
+            inputs={"a": a, "b": b},
+            outputs={"c": c})
+    imported = load.load(path)
+    path2 = os.path.join(self.get_temp_dir(), "saved_model", str(ops.uid()))
+    save.save(imported, path2, imported.signatures)
+
+    imported2 = load.load(path2)
+    self.assertEqual(
+        imported2.signatures["serving_default"](
+            a=constant_op.constant([5.]),
+            b=constant_op.constant([1., 3.]))["c"].numpy(), 5.)
+
 
 if __name__ == "__main__":
   test.main()