[Dy2Static]Enhance check of TracedLayers out vars (#30576)

python/paddle/fluid/dygraph/jit.py

@@ -53,21 +53,21 @@ def create_program_from_desc(program_desc):
     return program
 
 
-def _extract_vars(inputs, result_list):
+def _extract_vars(inputs, result_list, err_tag='inputs'):
     if isinstance(inputs, Variable):
         result_list.append(inputs)
     elif isinstance(inputs, (list, tuple)):
         for var in inputs:
-            _extract_vars(var, result_list)
+            _extract_vars(var, result_list, err_tag)
     else:
         raise TypeError(
-            "The type of 'each element of inputs' in fluid.dygraph.jit.TracedLayer.trace must be fluid.Variable, but received {}.".
+            "The type of 'each element of {}' in fluid.dygraph.jit.TracedLayer.trace must be fluid.Variable, but received {}.".
-            format(type(inputs)))
+            format(err_tag, type(inputs)))
 
 
-def extract_vars(inputs):
+def extract_vars(inputs, err_tag='inputs'):
     result_list = []
-    _extract_vars(inputs, result_list)
+    _extract_vars(inputs, result_list, err_tag)
     return result_list
 
 
@@ -1032,7 +1032,7 @@ def _trace(layer,
             outputs = [original_outputs]
         else:
             outputs = original_outputs
-        out_vars = [var for var in outputs]
+        out_vars = extract_vars(outputs, err_tag='outputs')
 
         program_desc, feed_names, fetch_names, parameters = tracer.create_program_desc(
             var_list, feed_prefix, out_vars, fetch_prefix, tmp_prefix)

python/paddle/fluid/tests/unittests/test_traced_layer_err_msg.py

@@ -13,16 +13,18 @@
 # limitations under the License.
 
 import numpy as np
+import paddle
 import paddle.fluid as fluid
 import six
 import unittest
+import paddle.nn as nn
 
 
-class SimpleFCLayer(fluid.dygraph.Layer):
+class SimpleFCLayer(nn.Layer):
     def __init__(self, feature_size, batch_size, fc_size):
         super(SimpleFCLayer, self).__init__()
-        self._linear = fluid.dygraph.Linear(feature_size, fc_size)
+        self._linear = nn.Linear(feature_size, fc_size)
-        self._offset = fluid.dygraph.to_variable(
+        self._offset = paddle.to_tensor(
             np.random.random((batch_size, fc_size)).astype('float32'))
 
     def forward(self, x):
@@ -30,6 +32,17 @@ class SimpleFCLayer(fluid.dygraph.Layer):
         return fc + self._offset
 
 
+class LinearNetWithNone(nn.Layer):
+    def __init__(self, feature_size, fc_size):
+        super(LinearNetWithNone, self).__init__()
+        self._linear = nn.Linear(feature_size, fc_size)
+
+    def forward(self, x):
+        fc = self._linear(x)
+
+        return [fc, [None, 2]]
+
+
 class TestTracedLayerErrMsg(unittest.TestCase):
     def setUp(self):
         self.batch_size = 4
@@ -152,5 +165,14 @@ class TestTracedLayerErrMsg(unittest.TestCase):
         return layer
 
 
+class TestOutVarWithNoneErrMsg(unittest.TestCase):
+    def test_linear_net_with_none(self):
+        model = LinearNetWithNone(100, 16)
+        in_x = paddle.to_tensor(np.random.random((4, 100)).astype('float32'))
+        with self.assertRaises(TypeError):
+            dygraph_out, traced_layer = fluid.dygraph.TracedLayer.trace(model,
+                                                                        [in_x])
+
+
 if __name__ == '__main__':
     unittest.main()