Add methods to update and verify out_features out_indices (#23031)

* Add methods to update and verify out_features out_indices

* Safe update for config attributes

* Fix function names

* Save config correctly

* PR comments - use property setters

* PR comment - directly set attributes

* Update test

* Add updates to recently merged focalnet backbone

tests/test_backbone_common.py

@@ -81,9 +81,15 @@ class BackboneTesterMixin:
             out_channels = [num_features[idx] for idx in out_indices]
             self.assertListEqual(model.channels, out_channels)
 
-            config.out_features = None
-            config.out_indices = None
-            model = model_class(config)
+            new_config = copy.deepcopy(config)
+            new_config.out_features = None
+            model = model_class(new_config)
+            self.assertEqual(len(model.channels), 1)
+            self.assertListEqual(model.channels, [num_features[-1]])
+
+            new_config = copy.deepcopy(config)
+            new_config.out_indices = None
+            model = model_class(new_config)
             self.assertEqual(len(model.channels), 1)
             self.assertListEqual(model.channels, [num_features[-1]])
 
@@ -102,6 +108,15 @@ class BackboneTesterMixin:
             # Check output of last stage is taken if out_features=None, out_indices=None
             modified_config = copy.deepcopy(config)
             modified_config.out_features = None
+            model = model_class(modified_config)
+            model.to(torch_device)
+            model.eval()
+            result = model(**inputs_dict)
+
+            self.assertEqual(len(result.feature_maps), 1)
+            self.assertEqual(len(model.channels), 1)
+
+            modified_config = copy.deepcopy(config)
             modified_config.out_indices = None
             model = model_class(modified_config)
             model.to(torch_device)

tests/utils/test_backbone_utils.py

@@ -0,0 +1,102 @@
+# Copyright 2023 The HuggingFace Team. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import unittest
+
+from transformers.utils.backbone_utils import (
+    BackboneMixin,
+    get_aligned_output_features_output_indices,
+    verify_out_features_out_indices,
+)
+
+
+class BackboneUtilsTester(unittest.TestCase):
+    def test_get_aligned_output_features_output_indices(self):
+        stage_names = ["a", "b", "c"]
+
+        # Defaults to last layer if both are None
+        out_features, out_indices = get_aligned_output_features_output_indices(None, None, stage_names)
+        self.assertEqual(out_features, ["c"])
+        self.assertEqual(out_indices, [2])
+
+        # Out indices set to match out features
+        out_features, out_indices = get_aligned_output_features_output_indices(["a", "c"], None, stage_names)
+        self.assertEqual(out_features, ["a", "c"])
+        self.assertEqual(out_indices, [0, 2])
+
+        # Out features set to match out indices
+        out_features, out_indices = get_aligned_output_features_output_indices(None, [0, 2], stage_names)
+        self.assertEqual(out_features, ["a", "c"])
+        self.assertEqual(out_indices, [0, 2])
+
+        # Out features selected from negative indices
+        out_features, out_indices = get_aligned_output_features_output_indices(None, [-3, -1], stage_names)
+        self.assertEqual(out_features, ["a", "c"])
+        self.assertEqual(out_indices, [-3, -1])
+
+    def test_verify_out_features_out_indices(self):
+        # Stage names must be set
+        with self.assertRaises(ValueError):
+            verify_out_features_out_indices(["a", "b"], (0, 1), None)
+
+        # Out features must be a list
+        with self.assertRaises(ValueError):
+            verify_out_features_out_indices(("a", "b"), (0, 1), ["a", "b"])
+
+        # Out features must be a subset of stage names
+        with self.assertRaises(ValueError):
+            verify_out_features_out_indices(["a", "b"], (0, 1), ["a"])
+
+        # Out indices must be a list or tuple
+        with self.assertRaises(ValueError):
+            verify_out_features_out_indices(None, 0, ["a", "b"])
+
+        # Out indices must be a subset of stage names
+        with self.assertRaises(ValueError):
+            verify_out_features_out_indices(None, (0, 1), ["a"])
+
+        # Out features and out indices must be the same length
+        with self.assertRaises(ValueError):
+            verify_out_features_out_indices(["a", "b"], (0,), ["a", "b", "c"])
+
+        # Out features should match out indices
+        with self.assertRaises(ValueError):
+            verify_out_features_out_indices(["a", "b"], (0, 2), ["a", "b", "c"])
+
+        # Out features and out indices should be in order
+        with self.assertRaises(ValueError):
+            verify_out_features_out_indices(["b", "a"], (0, 1), ["a", "b"])
+
+        # Check passes with valid inputs
+        verify_out_features_out_indices(["a", "b", "d"], (0, 1, -1), ["a", "b", "c", "d"])
+
+    def test_backbone_mixin(self):
+        backbone = BackboneMixin()
+
+        backbone.stage_names = ["a", "b", "c"]
+        backbone._out_features = ["a", "c"]
+        backbone._out_indices = [0, 2]
+
+        # Check that the output features and indices are set correctly
+        self.assertEqual(backbone.out_features, ["a", "c"])
+        self.assertEqual(backbone.out_indices, [0, 2])
+
+        # Check out features and indices are updated correctly
+        backbone.out_features = ["a", "b"]
+        self.assertEqual(backbone.out_features, ["a", "b"])
+        self.assertEqual(backbone.out_indices, [0, 1])
+
+        backbone.out_indices = [-3, -1]
+        self.assertEqual(backbone.out_features, ["a", "c"])
+        self.assertEqual(backbone.out_indices, [-3, -1])