[MBartTokenizer] remove dep on xlm-roberta tokenizer (#15201)

src/transformers/models/mbart/tokenization_mbart.py

@@ -13,16 +13,20 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import os
 from contextlib import contextmanager
-from typing import List, Optional
+from shutil import copyfile
+from typing import Any, Dict, List, Optional, Tuple
 
-from ...tokenization_utils import BatchEncoding
+import sentencepiece as spm
+
+from ...tokenization_utils import AddedToken, BatchEncoding, PreTrainedTokenizer
 from ...utils import logging
-from ..xlm_roberta.tokenization_xlm_roberta import XLMRobertaTokenizer
 
 
 logger = logging.get_logger(__name__)
 
+SPIECE_UNDERLINE = "▁"
 
 VOCAB_FILES_NAMES = {"vocab_file": "sentencepiece.bpe.model"}
 
@@ -38,41 +42,17 @@
     "facebook/mbart-large-cc25": 1024,
 }
 
-FAIRSEQ_LANGUAGE_CODES = [
-    "ar_AR",
-    "cs_CZ",
-    "de_DE",
-    "en_XX",
-    "es_XX",
-    "et_EE",
-    "fi_FI",
-    "fr_XX",
-    "gu_IN",
-    "hi_IN",
-    "it_IT",
-    "ja_XX",
-    "kk_KZ",
-    "ko_KR",
-    "lt_LT",
-    "lv_LV",
-    "my_MM",
-    "ne_NP",
-    "nl_XX",
-    "ro_RO",
-    "ru_RU",
-    "si_LK",
-    "tr_TR",
-    "vi_VN",
-    "zh_CN",
-]
-
-
-class MBartTokenizer(XLMRobertaTokenizer):
+# fmt: off
+FAIRSEQ_LANGUAGE_CODES = ["ar_AR", "cs_CZ", "de_DE", "en_XX", "es_XX", "et_EE", "fi_FI", "fr_XX", "gu_IN", "hi_IN", "it_IT", "ja_XX", "kk_KZ", "ko_KR", "lt_LT", "lv_LV", "my_MM", "ne_NP", "nl_XX", "ro_RO", "ru_RU", "si_LK", "tr_TR", "vi_VN", "zh_CN"]
+# fmt: on
+
+
+class MBartTokenizer(PreTrainedTokenizer):
     """
     Construct an MBART tokenizer.
 
-    [`MBartTokenizer`] is a subclass of [`XLMRobertaTokenizer`]. Refer to superclass [`XLMRobertaTokenizer`] for usage
-    examples and documentation concerning the initialization parameters and other methods.
+    Adapted from [`RobertaTokenizer`] and [`XLNetTokenizer`]. Based on
+    [SentencePiece](https://github.com/google/sentencepiece).
 
     The tokenization method is `<tokens> <eos> <language code>` for source language documents, and ``<language code>
     <tokens> <eos>``` for target language documents.
@@ -94,22 +74,66 @@ class MBartTokenizer(XLMRobertaTokenizer):
     vocab_files_names = VOCAB_FILES_NAMES
     max_model_input_sizes = PRETRAINED_POSITIONAL_EMBEDDINGS_SIZES
     pretrained_vocab_files_map = PRETRAINED_VOCAB_FILES_MAP
+    model_input_names = ["input_ids", "attention_mask"]
 
     prefix_tokens: List[int] = []
     suffix_tokens: List[int] = []
 
     def __init__(
-        self, *args, tokenizer_file=None, src_lang=None, tgt_lang=None, additional_special_tokens=None, **kwargs
+        self,
+        vocab_file,
+        bos_token="<s>",
+        eos_token="</s>",
+        sep_token="</s>",
+        cls_token="<s>",
+        unk_token="<unk>",
+        pad_token="<pad>",
+        mask_token="<mask>",
+        tokenizer_file=None,
+        src_lang=None,
+        tgt_lang=None,
+        sp_model_kwargs: Optional[Dict[str, Any]] = None,
+        additional_special_tokens=None,
+        **kwargs
     ):
+
+        # Mask token behave like a normal word, i.e. include the space before it
+        mask_token = AddedToken(mask_token, lstrip=True, rstrip=False) if isinstance(mask_token, str) else mask_token
+
+        self.sp_model_kwargs = {} if sp_model_kwargs is None else sp_model_kwargs
+
         super().__init__(
-            *args,
+            bos_token=bos_token,
+            eos_token=eos_token,
+            unk_token=unk_token,
+            sep_token=sep_token,
+            cls_token=cls_token,
+            pad_token=pad_token,
+            mask_token=mask_token,
             tokenizer_file=tokenizer_file,
             src_lang=src_lang,
             tgt_lang=tgt_lang,
             additional_special_tokens=additional_special_tokens,
+            sp_model_kwargs=self.sp_model_kwargs,
             **kwargs,
         )
 
+        self.sp_model = spm.SentencePieceProcessor(**self.sp_model_kwargs)
+        self.sp_model.Load(str(vocab_file))
+        self.vocab_file = vocab_file
+
+        # Original fairseq vocab and spm vocab must be "aligned":
+        # Vocab    |    0    |    1    |   2    |    3    |  4  |  5  |  6  |   7   |   8   |  9
+        # -------- | ------- | ------- | ------ | ------- | --- | --- | --- | ----- | ----- | ----
+        # fairseq  | '<s>'   | '<pad>' | '</s>' | '<unk>' | ',' | '.' | '▁' | 's'   | '▁de' | '-'
+        # spm      | '<unk>' | '<s>'   | '</s>' | ','     | '.' | '▁' | 's' | '▁de' | '-'   | '▁a'
+
+        # Mimic fairseq token-to-id alignment for the first 4 token
+        self.fairseq_tokens_to_ids = {"<s>": 0, "<pad>": 1, "</s>": 2, "<unk>": 3}
+
+        # The first "real" token "," has position 4 in the original fairseq vocab and position 3 in the spm vocab
+        self.fairseq_offset = 1
+
         self.sp_model_size = len(self.sp_model)
         self.lang_code_to_id = {
             code: self.sp_model_size + i + self.fairseq_offset for i, code in enumerate(FAIRSEQ_LANGUAGE_CODES)
@@ -132,6 +156,22 @@ def __init__(
         self.tgt_lang = tgt_lang
         self.set_src_lang_special_tokens(self._src_lang)
 
+    def __getstate__(self):
+        state = self.__dict__.copy()
+        state["sp_model"] = None
+        state["sp_model_proto"] = self.sp_model.serialized_model_proto()
+        return state
+
+    def __setstate__(self, d):
+        self.__dict__ = d
+
+        # for backward compatibility
+        if not hasattr(self, "sp_model_kwargs"):
+            self.sp_model_kwargs = {}
+
+        self.sp_model = spm.SentencePieceProcessor(**self.sp_model_kwargs)
+        self.sp_model.LoadFromSerializedProto(self.sp_model_proto)
+
     @property
     def vocab_size(self):
         return len(self.sp_model) + len(self.lang_code_to_id) + self.fairseq_offset + 1  # Plus 1 for the mask token
@@ -202,6 +242,31 @@ def build_inputs_with_special_tokens(
         # We don't expect to process pairs, but leave the pair logic for API consistency
         return self.prefix_tokens + token_ids_0 + token_ids_1 + self.suffix_tokens
 
+    def create_token_type_ids_from_sequences(
+        self, token_ids_0: List[int], token_ids_1: Optional[List[int]] = None
+    ) -> List[int]:
+        """
+        Create a mask from the two sequences passed to be used in a sequence-pair classification task. mBART does not
+        make use of token type ids, therefore a list of zeros is returned.
+
+        Args:
+            token_ids_0 (`List[int]`):
+                List of IDs.
+            token_ids_1 (`List[int]`, *optional*):
+                Optional second list of IDs for sequence pairs.
+
+        Returns:
+            `List[int]`: List of zeros.
+
+        """
+
+        sep = [self.sep_token_id]
+        cls = [self.cls_token_id]
+
+        if token_ids_1 is None:
+            return len(cls + token_ids_0 + sep) * [0]
+        return len(cls + token_ids_0 + sep + sep + token_ids_1 + sep) * [0]
+
     def _build_translation_inputs(
         self, raw_inputs, return_tensors: str, src_lang: Optional[str], tgt_lang: Optional[str], **extra_kwargs
     ):
@@ -214,6 +279,47 @@ def _build_translation_inputs(
         inputs["forced_bos_token_id"] = tgt_lang_id
         return inputs
 
+    def get_vocab(self):
+        vocab = {self.convert_ids_to_tokens(i): i for i in range(self.vocab_size)}
+        vocab.update(self.added_tokens_encoder)
+        return vocab
+
+    def _tokenize(self, text: str) -> List[str]:
+        return self.sp_model.encode(text, out_type=str)
+
+    def _convert_token_to_id(self, token):
+        """Converts a token (str) in an id using the vocab."""
+        if token in self.fairseq_tokens_to_ids:
+            return self.fairseq_tokens_to_ids[token]
+        spm_id = self.sp_model.PieceToId(token)
+
+        # Need to return unknown token if the SP model returned 0
+        return spm_id + self.fairseq_offset if spm_id else self.unk_token_id
+
+    def _convert_id_to_token(self, index):
+        """Converts an index (integer) in a token (str) using the vocab."""
+        if index in self.fairseq_ids_to_tokens:
+            return self.fairseq_ids_to_tokens[index]
+        return self.sp_model.IdToPiece(index - self.fairseq_offset)
+
+    def convert_tokens_to_string(self, tokens):
+        """Converts a sequence of tokens (strings for sub-words) in a single string."""
+        out_string = "".join(tokens).replace(SPIECE_UNDERLINE, " ").strip()
+        return out_string
+
+    def save_vocabulary(self, save_directory: str, filename_prefix: Optional[str] = None) -> Tuple[str]:
+        if not os.path.isdir(save_directory):
+            logger.error(f"Vocabulary path ({save_directory}) should be a directory")
+            return
+        out_vocab_file = os.path.join(
+            save_directory, (filename_prefix + "-" if filename_prefix else "") + VOCAB_FILES_NAMES["vocab_file"]
+        )
+
+        if os.path.abspath(self.vocab_file) != os.path.abspath(out_vocab_file):
+            copyfile(self.vocab_file, out_vocab_file)
+
+        return (out_vocab_file,)
+
     def prepare_seq2seq_batch(
         self,
         src_texts: List[str],