Support save model in dygraph.guard test=develop (#24761)

python/paddle/fluid/dygraph/dygraph_to_static/program_translator.py

@@ -550,6 +550,7 @@ class ProgramTranslator(object):
         source_code = ast_to_source_code(root_wrapper.node)
         return source_code
 
+    @switch_to_static_graph
     def save_inference_model(self, dirname, feed=None, fetch=None):
         """
         Saves current model as the inference model. It will prune the main_program

python/paddle/fluid/tests/unittests/dygraph_to_static/test_mnist.py

@@ -200,7 +200,6 @@ class TestMNISTWithDeclarative(TestMNIST):
                         break
         return loss_data
 
-    @switch_to_static_graph
     def check_save_inference_model(self, inputs, prog_trans, to_static, gt_out):
         if to_static:
             infer_model_path = "./test_mnist_inference_model"
@@ -208,6 +207,7 @@ class TestMNISTWithDeclarative(TestMNIST):
             infer_out = self.load_and_run_inference(infer_model_path, inputs)
             self.assertTrue(np.allclose(gt_out.numpy(), infer_out))
 
+    @switch_to_static_graph
     def load_and_run_inference(self, model_path, inputs):
         exe = fluid.Executor(self.place)
         [inference_program, feed_target_names,

python/paddle/fluid/tests/unittests/dygraph_to_static/test_save_inference_model.py

@@ -30,6 +30,7 @@ np.random.seed(SEED)
 
 place = fluid.CUDAPlace(0) if fluid.is_compiled_with_cuda() else fluid.CPUPlace(
 )
+program_translator = ProgramTranslator()
 
 
 class SimpleFcLayer(fluid.dygraph.Layer):
@@ -63,6 +64,10 @@ class TestDyToStaticSaveInferenceModel(unittest.TestCase):
                 loss.backward()
                 adam.minimize(loss)
                 layer.clear_gradients()
+            # test for saving model in dygraph.guard
+            infer_model_dir = "./test_dy2stat_save_inference_model"
+            program_translator.save_inference_model(
+                infer_model_dir, feed=[0], fetch=[1])
             # Check the correctness of the inference
             dygraph_out, _ = layer(x)
         self.check_save_inference_model(layer, [x_data], dygraph_out.numpy())
@@ -77,7 +82,7 @@ class TestDyToStaticSaveInferenceModel(unittest.TestCase):
                                    gt_out,
                                    feed=None,
                                    fetch=None):
-        program_translator = ProgramTranslator()
+
         expected_persistable_vars = set([p.name for p in model.parameters()])
 
         infer_model_dir = "./test_dy2stat_save_inference_model"