fix BertTokenizerFast `tokenize_chinese_chars` arg (#15158)

* add new test

* fix in init

* more relevant test

src/transformers/models/bert/tokenization_bert_fast.py

@@ -188,15 +188,17 @@ class BertTokenizerFast(PreTrainedTokenizerFast):
             **kwargs,
         )
 
-        pre_tok_state = json.loads(self.backend_tokenizer.normalizer.__getstate__())
+        normalizer_state = json.loads(self.backend_tokenizer.normalizer.__getstate__())
         if (
-            pre_tok_state.get("lowercase", do_lower_case) != do_lower_case
-            or pre_tok_state.get("strip_accents", strip_accents) != strip_accents
+            normalizer_state.get("lowercase", do_lower_case) != do_lower_case
+            or normalizer_state.get("strip_accents", strip_accents) != strip_accents
+            or normalizer_state.get("handle_chinese_chars", tokenize_chinese_chars) != tokenize_chinese_chars
         ):
-            pre_tok_class = getattr(normalizers, pre_tok_state.pop("type"))
-            pre_tok_state["lowercase"] = do_lower_case
-            pre_tok_state["strip_accents"] = strip_accents
-            self.backend_tokenizer.normalizer = pre_tok_class(**pre_tok_state)
+            normalizer_class = getattr(normalizers, normalizer_state.pop("type"))
+            normalizer_state["lowercase"] = do_lower_case
+            normalizer_state["strip_accents"] = strip_accents
+            normalizer_state["handle_chinese_chars"] = tokenize_chinese_chars
+            self.backend_tokenizer.normalizer = normalizer_class(**normalizer_state)
 
         self.do_lower_case = do_lower_case
 

tests/test_tokenization_bert.py

@@ -299,3 +299,40 @@ class BertTokenizationTest(TokenizerTesterMixin, unittest.TestCase):
                     [e[1] for e in expected_results], tokenizer_r.convert_ids_to_tokens(tokens["input_ids"])
                 )
                 self.assertEqual([e[0] for e in expected_results], tokens["offset_mapping"])
+
+    def test_change_tokenize_chinese_chars(self):
+        list_of_commun_chinese_char = ["的", "人", "有"]
+        text_with_chinese_char = "".join(list_of_commun_chinese_char)
+        for tokenizer, pretrained_name, kwargs in self.tokenizers_list:
+            with self.subTest(f"{tokenizer.__class__.__name__} ({pretrained_name})"):
+
+                kwargs["tokenize_chinese_chars"] = True
+                tokenizer_p = self.tokenizer_class.from_pretrained(pretrained_name, **kwargs)
+                tokenizer_r = self.rust_tokenizer_class.from_pretrained(pretrained_name, **kwargs)
+
+                ids_without_spe_char_p = tokenizer_p.encode(text_with_chinese_char, add_special_tokens=False)
+                ids_without_spe_char_r = tokenizer_r.encode(text_with_chinese_char, add_special_tokens=False)
+
+                tokens_without_spe_char_r = tokenizer_r.convert_ids_to_tokens(ids_without_spe_char_r)
+                tokens_without_spe_char_p = tokenizer_p.convert_ids_to_tokens(ids_without_spe_char_p)
+
+                # it is expected that each Chinese character is not preceded by "##"
+                self.assertListEqual(tokens_without_spe_char_p, list_of_commun_chinese_char)
+                self.assertListEqual(tokens_without_spe_char_r, list_of_commun_chinese_char)
+
+                kwargs["tokenize_chinese_chars"] = False
+                tokenizer_r = self.rust_tokenizer_class.from_pretrained(pretrained_name, **kwargs)
+                tokenizer_p = self.tokenizer_class.from_pretrained(pretrained_name, **kwargs)
+
+                ids_without_spe_char_r = tokenizer_r.encode(text_with_chinese_char, add_special_tokens=False)
+                ids_without_spe_char_p = tokenizer_p.encode(text_with_chinese_char, add_special_tokens=False)
+
+                tokens_without_spe_char_r = tokenizer_r.convert_ids_to_tokens(ids_without_spe_char_r)
+                tokens_without_spe_char_p = tokenizer_p.convert_ids_to_tokens(ids_without_spe_char_p)
+
+                # it is expected that only the first Chinese character is not preceded by "##".
+                expected_tokens = [
+                    f"##{token}" if idx != 0 else token for idx, token in enumerate(list_of_commun_chinese_char)
+                ]
+                self.assertListEqual(tokens_without_spe_char_p, expected_tokens)
+                self.assertListEqual(tokens_without_spe_char_r, expected_tokens)