Allow flax subfolder (#19902)

* add first generation tutorial

* [Flax] Add subfolder functionality

* [Flax] Add subfolder functionality

* up

* finish

* delete file and re-add test

tests/test_modeling_flax_common.py

@@ -1221,3 +1221,68 @@ class FlaxModelPushToHubTester(unittest.TestCase):
         for key in base_params.keys():
             max_diff = (base_params[key] - new_params[key]).sum().item()
             self.assertLessEqual(max_diff, 1e-3, msg=f"{key} not identical")
+
+
+def check_models_equal(model1, model2):
+    models_are_equal = True
+    flat_params_1 = flatten_dict(model1.params)
+    flat_params_2 = flatten_dict(model2.params)
+    for key in flat_params_1.keys():
+        if np.sum(np.abs(flat_params_1[key] - flat_params_2[key])) > 1e-4:
+            models_are_equal = False
+
+    return models_are_equal
+
+
+@require_flax
+class FlaxModelUtilsTest(unittest.TestCase):
+    def test_model_from_pretrained_subfolder(self):
+        config = BertConfig.from_pretrained("hf-internal-testing/tiny-bert-flax-only")
+        model = FlaxBertModel(config)
+
+        subfolder = "bert"
+        with tempfile.TemporaryDirectory() as tmp_dir:
+            model.save_pretrained(os.path.join(tmp_dir, subfolder))
+
+            with self.assertRaises(OSError):
+                _ = FlaxBertModel.from_pretrained(tmp_dir)
+
+            model_loaded = FlaxBertModel.from_pretrained(tmp_dir, subfolder=subfolder)
+
+        self.assertTrue(check_models_equal(model, model_loaded))
+
+    def test_model_from_pretrained_subfolder_sharded(self):
+        config = BertConfig.from_pretrained("hf-internal-testing/tiny-bert-flax-only")
+        model = FlaxBertModel(config)
+
+        subfolder = "bert"
+        with tempfile.TemporaryDirectory() as tmp_dir:
+            model.save_pretrained(os.path.join(tmp_dir, subfolder), max_shard_size="10KB")
+
+            with self.assertRaises(OSError):
+                _ = FlaxBertModel.from_pretrained(tmp_dir)
+
+            model_loaded = FlaxBertModel.from_pretrained(tmp_dir, subfolder=subfolder)
+
+        self.assertTrue(check_models_equal(model, model_loaded))
+
+    def test_model_from_pretrained_hub_subfolder(self):
+        subfolder = "bert"
+        model_id = "hf-internal-testing/tiny-random-bert-subfolder"
+
+        with self.assertRaises(OSError):
+            _ = FlaxBertModel.from_pretrained(model_id)
+
+        model = FlaxBertModel.from_pretrained(model_id, subfolder=subfolder)
+
+        self.assertIsNotNone(model)
+
+    def test_model_from_pretrained_hub_subfolder_sharded(self):
+        subfolder = "bert"
+        model_id = "hf-internal-testing/tiny-random-bert-sharded-subfolder"
+        with self.assertRaises(OSError):
+            _ = FlaxBertModel.from_pretrained(model_id)
+
+        model = FlaxBertModel.from_pretrained(model_id, subfolder=subfolder)
+
+        self.assertIsNotNone(model)