Fix bug huggingface#35447 Tokenizer does not split text according to …

…newly added input tokens

The root reason is Trie.split method didn't ignore partial match that should be removed

Add test case to token split

src/transformers/tokenization_utils.py

@@ -175,7 +175,10 @@ def split(self, text: str) -> List[str]:
                     # matches
                     # "[CLS]", "L", we need to match CLS even if L is special
                     for lookstart, looktrie_pointer in states.items():
-                        if lookstart > start:
+                        if lookstart in to_remove:
+                            # This partial match should be removed
+                            continue
+                        elif lookstart > start:
                             # This partial match is later, we can stop looking
                             break
                         elif lookstart < start:

tests/tokenization/test_tokenization_utils.py

@@ -367,6 +367,18 @@ def test_decoding_skip_special_tokens(self):
                 decoded_sent = tokenizer.decode(pad_id, skip_special_tokens=False)
                 self.assertEqual(decoded_sent, "[PAD]")
 
+    @require_tokenizers
+    def test_split_tokens(self):
+        for tokenizer_class in [BertTokenizer, BertTokenizerFast]:
+            with self.subTest(f"{tokenizer_class}"):
+                tokenizer = tokenizer_class.from_pretrained("google-bert/bert-base-cased")
+                tokenizer.add_tokens(["red", "e"])
+
+                # test split tokens
+                sentence = "read"
+                output_tokens = tokenizer.tokenize(sentence)
+                self.assertEqual(output_tokens, ["r", "e", "ad"])
+
     @require_torch
     def test_padding_accepts_tensors_pt(self):
         import torch