replace assert with exception for padding_side arg in PreTrainedTokenizerBase __init__ (#15454)

* replace assert with exception for `padding_side` arg in `PreTrainedTokenizerBase` `__init__`

* add test

* fix kwargs

* reformat test

* format

* format

* fix typo to render the documentation

src/transformers/tokenization_utils_base.py

@@ -1389,7 +1389,7 @@ INIT_TOKENIZER_DOCSTRING = r"""
             loaded with [`~tokenization_utils_base.PreTrainedTokenizerBase.from_pretrained`], this will be set to the
             value stored for the associated model in `max_model_input_sizes` (see above). If no value is provided, will
             default to VERY_LARGE_INTEGER (`int(1e30)`).
-        padding_side: (`str`, *optional*):
+        padding_side (`str`, *optional*):
             The side on which the model should have padding applied. Should be selected between ['right', 'left'].
             Default value is picked from the class attribute of the same name.
         model_input_names (`List[string]`, *optional*):
@@ -1456,10 +1456,10 @@ class PreTrainedTokenizerBase(SpecialTokensMixin, PushToHubMixin):
 
         # Padding side is right by default and overridden in subclasses. If specified in the kwargs, it is changed.
         self.padding_side = kwargs.pop("padding_side", self.padding_side)
-        assert self.padding_side in [
-            "right",
-            "left",
-        ], f"Padding side should be selected between 'right' and 'left', current value: {self.padding_side}"
+        if self.padding_side not in ["right", "left"]:
+            raise ValueError(
+                f"Padding side should be selected between 'right' and 'left', current value: {self.padding_side}"
+            )
         self.model_input_names = kwargs.pop("model_input_names", self.model_input_names)
 
         self.deprecation_warnings = (

tests/test_tokenization_common.py

@@ -1367,6 +1367,43 @@ class TokenizerTesterMixin:
                 filtered_sequence = [x for x in filtered_sequence if x is not None]
                 self.assertEqual(encoded_sequence, filtered_sequence)
 
+    def test_padding_side_in_kwargs(self):
+        for tokenizer, pretrained_name, kwargs in self.tokenizers_list:
+            with self.subTest(f"{tokenizer.__class__.__name__} ({pretrained_name})"):
+                if self.test_rust_tokenizer:
+                    tokenizer_r = self.rust_tokenizer_class.from_pretrained(
+                        pretrained_name, padding_side="left", **kwargs
+                    )
+                    self.assertEqual(tokenizer_r.padding_side, "left")
+
+                    tokenizer_r = self.rust_tokenizer_class.from_pretrained(
+                        pretrained_name, padding_side="right", **kwargs
+                    )
+                    self.assertEqual(tokenizer_r.padding_side, "right")
+
+                    self.assertRaises(
+                        ValueError,
+                        self.rust_tokenizer_class.from_pretrained,
+                        pretrained_name,
+                        padding_side="unauthorized",
+                        **kwargs,
+                    )
+
+                if self.test_slow_tokenizer:
+                    tokenizer_p = self.tokenizer_class.from_pretrained(pretrained_name, padding_side="left", **kwargs)
+                    self.assertEqual(tokenizer_p.padding_side, "left")
+
+                    tokenizer_p = self.tokenizer_class.from_pretrained(pretrained_name, padding_side="right", **kwargs)
+                    self.assertEqual(tokenizer_p.padding_side, "right")
+
+                    self.assertRaises(
+                        ValueError,
+                        self.tokenizer_class.from_pretrained,
+                        pretrained_name,
+                        padding_side="unauthorized",
+                        **kwargs,
+                    )
+
     def test_right_and_left_padding(self):
         tokenizers = self.get_tokenizers(do_lower_case=False)
         for tokenizer in tokenizers: