Support for additional_special_tokens (#1221) [skip ci]

* Support for additional_special_tokens

* Support for additional_special_tokens. Adjust whitespace.

* Support for additional_special_tokens. Use correct quotes.

* Support for additional_special_tokens. Safe pop.

* Support for additional_special_tokens. nt.

* Support for additional_special_tokens. cfg.special_tokens may be None.

* add token if not in vocabulary when adding additional_special_tokens

* fix logic for copy/pasta

* bugfix for popping from config and tokenizer reload

* no need to add tokens manually now with previous bugfix

---------

Co-authored-by: Wing Lian <wing.lian@gmail.com>

src/axolotl/utils/models.py

@@ -161,15 +161,20 @@ def load_tokenizer(cfg):
             if getattr(tokenizer, attr_name) is None:
                 setattr(tokenizer, attr_name, "<|endoftext|>")
 
+    additional_special_tokens = None
     if cfg.special_tokens:
+        special_tokens = cfg.special_tokens.to_dict()
+        additional_special_tokens = special_tokens.pop(
+            "additional_special_tokens", None
+        )
         lora_modules_to_save = get_linear_embedding_layers(model_config.model_type)
-        for k, val in cfg.special_tokens.items():
+        for k, val in special_tokens.items():
             # check if new special token is not already in tokenizer and
             # is adapter training to make sure lora_modules_to_save is set
             # pylint: disable=too-many-boolean-expressions
             if (
                 (getattr(tokenizer, k) is None or getattr(tokenizer, k) != val)
-                and (len(tokenizer.encode(val)) > 1)
+                and (len(tokenizer.encode(val, add_special_tokens=False)) > 2)
                 and cfg.adapter
                 and (
                     not cfg.lora_modules_to_save
@@ -213,6 +218,21 @@ def load_tokenizer(cfg):
             ]
         )
 
+    # Additional special tokens are a List, and need to be treated differently than regular special
+    # tokens. We add them after we have called `add_tokens` in case these additional special tokens
+    # are new tokens.
+    #
+    # Usage:
+    #
+    # ```py
+    # special_tokens:
+    #   additional_special_tokens: ["<|im_start|>", "<|im_end|>"]
+    # ```
+    if additional_special_tokens is not None:
+        tokenizer.add_special_tokens(
+            {"additional_special_tokens": additional_special_tokens}
+        )
+
     LOG.debug(f"EOS: {tokenizer.eos_token_id} / {tokenizer.eos_token}")
     LOG.debug(f"BOS: {tokenizer.bos_token_id} / {tokenizer.bos_token}")
     LOG.debug(f"PAD: {tokenizer.pad_token_id} / {tokenizer.pad_token}")

tests/test_tokenizers.py

@@ -67,6 +67,21 @@ class TestTokenizers(unittest.TestCase):
         )
         load_tokenizer(cfg)
 
+    def test_add_additional_special_tokens(self):
+        cfg = DictDefault(
+            {
+                "tokenizer_config": "huggyllama/llama-7b",
+                "special_tokens": {"additional_special_tokens": ["<|im_start|>"]},
+            }
+        )
+        tokenizer = load_tokenizer(cfg)
+        self.assertEqual(tokenizer("<|im_start|>user")["input_ids"], [1, 32000, 1404])
+        self.assertEqual(len(tokenizer), 32001)
+
+        # ensure reloading the tokenizer again from cfg results in same vocab length
+        tokenizer = load_tokenizer(cfg)
+        self.assertEqual(len(tokenizer), 32001)
+
 
 if __name__ == "__main__":
     unittest.main()