tokenization_fsmt.py

# coding=utf-8
# Copyright 2019 The Open AI Team Authors and The HuggingFace Inc. team.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Tokenization classes for FSMT."""

import json
import os
import re
import unicodedata
from typing import Dict, List, Optional, Tuple

from ...tokenization_utils import PreTrainedTokenizer
from ...utils import logging


logger = logging.get_logger(__name__)

VOCAB_FILES_NAMES = {
    "src_vocab_file": "vocab-src.json",
    "tgt_vocab_file": "vocab-tgt.json",
    "merges_file": "merges.txt",
}


def get_pairs(word):
    """
    Return set of symbol pairs in a word. word is represented as tuple of symbols (symbols being variable-length
    strings)
    """
    pairs = set()
    prev_char = word[0]
    for char in word[1:]:
        pairs.add((prev_char, char))
        prev_char = char
    return pairs


def replace_unicode_punct(text):
    """
    Port of https://github.com/moses-smt/mosesdecoder/blob/master/scripts/tokenizer/replace-unicode-punctuation.perl
    """
    text = text.replace("，", ",")
    text = re.sub(r"。\s*", ". ", text)
    text = text.replace("、", ",")
    text = text.replace("”", '"')
    text = text.replace("“", '"')
    text = text.replace("∶", ":")
    text = text.replace("：", ":")
    text = text.replace("？", "?")
    text = text.replace("《", '"')
    text = text.replace("》", '"')
    text = text.replace("）", ")")
    text = text.replace("！", "!")
    text = text.replace("（", "(")
    text = text.replace("；", ";")
    text = text.replace("１", "1")
    text = text.replace("」", '"')
    text = text.replace("「", '"')
    text = text.replace("０", "0")
    text = text.replace("３", "3")
    text = text.replace("２", "2")
    text = text.replace("５", "5")
    text = text.replace("６", "6")
    text = text.replace("９", "9")
    text = text.replace("７", "7")
    text = text.replace("８", "8")
    text = text.replace("４", "4")
    text = re.sub(r"．\s*", ". ", text)
    text = text.replace("～", "~")
    text = text.replace("’", "'")
    text = text.replace("…", "...")
    text = text.replace("━", "-")
    text = text.replace("〈", "<")
    text = text.replace("〉", ">")
    text = text.replace("【", "[")
    text = text.replace("】", "]")
    text = text.replace("％", "%")
    return text


def remove_non_printing_char(text):
    """
    Port of https://github.com/moses-smt/mosesdecoder/blob/master/scripts/tokenizer/remove-non-printing-char.perl
    """
    output = []
    for char in text:
        cat = unicodedata.category(char)
        if cat.startswith("C"):
            continue
        output.append(char)
    return "".join(output)


# Porting notes:
# this one is modeled after XLMTokenizer
#
# added:
# - src_vocab_file,
# - tgt_vocab_file,
# - langs,


class FSMTTokenizer(PreTrainedTokenizer):
    """
    Construct an FAIRSEQ Transformer tokenizer. Based on Byte-Pair Encoding. The tokenization process is the following:

    - Moses preprocessing and tokenization.
    - Normalizing all inputs text.
    - The arguments `special_tokens` and the function `set_special_tokens`, can be used to add additional symbols (like
      "__classify__") to a vocabulary.
    - The argument `langs` defines a pair of languages.

    This tokenizer inherits from [`PreTrainedTokenizer`] which contains most of the main methods. Users should refer to
    this superclass for more information regarding those methods.

    Args:
        langs (`List[str]`, *optional*):
            A list of two languages to translate from and to, for instance `["en", "ru"]`.
        src_vocab_file (`str`, *optional*):
            File containing the vocabulary for the source language.
        tgt_vocab_file (`st`, *optional*):
            File containing the vocabulary for the target language.
        merges_file (`str`, *optional*):
            File containing the merges.
        do_lower_case (`bool`, *optional*, defaults to `False`):
            Whether or not to lowercase the input when tokenizing.
        unk_token (`str`, *optional*, defaults to `"<unk>"`):
            The unknown token. A token that is not in the vocabulary cannot be converted to an ID and is set to be this
            token instead.
        bos_token (`str`, *optional*, defaults to `"<s>"`):
            The beginning of sequence token that was used during pretraining. Can be used a sequence classifier token.

            <Tip>

            When building a sequence using special tokens, this is not the token that is used for the beginning of
            sequence. The token used is the `cls_token`.

            </Tip>

        sep_token (`str`, *optional*, defaults to `"</s>"`):
            The separator token, which is used when building a sequence from multiple sequences, e.g. two sequences for
            sequence classification or for a text and a question for question answering. It is also used as the last
            token of a sequence built with special tokens.
        pad_token (`str`, *optional*, defaults to `"<pad>"`):
            The token used for padding, for example when batching sequences of different lengths.

    """

    vocab_files_names = VOCAB_FILES_NAMES
    model_input_names = ["input_ids", "attention_mask"]

    def __init__(
        self,
        langs=None,
        src_vocab_file=None,
        tgt_vocab_file=None,
        merges_file=None,
        do_lower_case=False,
        unk_token="<unk>",
        bos_token="<s>",
        sep_token="</s>",
        pad_token="<pad>",
        **kwargs,
    ):
        try:
            import sacremoses
        except ImportError:
            raise ImportError(
                "You need to install sacremoses to use XLMTokenizer. "
                "See https://pypi.org/project/sacremoses/ for installation."
            )

        self.sm = sacremoses

        self.src_vocab_file = src_vocab_file
        self.tgt_vocab_file = tgt_vocab_file
        self.merges_file = merges_file
        self.do_lower_case = do_lower_case

        # cache of sm.MosesPunctNormalizer instance
        self.cache_moses_punct_normalizer = {}
        # cache of sm.MosesTokenizer instance
        self.cache_moses_tokenizer = {}
        self.cache_moses_detokenizer = {}

        if langs and len(langs) == 2:
            self.src_lang, self.tgt_lang = langs
        else:
            raise ValueError(
                f"arg `langs` needs to be a list of 2 langs, e.g. ['en', 'ru'], but got {langs}. "
                "Usually that means that tokenizer can't find a mapping for the given model path "
                "in  and other maps of this tokenizer."
            )

        with open(src_vocab_file, encoding="utf-8") as src_vocab_handle:
            self.encoder = json.load(src_vocab_handle)
        with open(tgt_vocab_file, encoding="utf-8") as tgt_vocab_handle:
            tgt_vocab = json.load(tgt_vocab_handle)
            self.decoder = {v: k for k, v in tgt_vocab.items()}
        with open(merges_file, encoding="utf-8") as merges_handle:
            merges = merges_handle.read().split("\n")[:-1]
        merges = [tuple(merge.split()[:2]) for merge in merges]
        self.bpe_ranks = dict(zip(merges, range(len(merges))))
        self.cache = {}
        super().__init__(
            langs=langs,
            src_vocab_file=src_vocab_file,
            tgt_vocab_file=tgt_vocab_file,
            merges_file=merges_file,
            do_lower_case=do_lower_case,
            unk_token=unk_token,
            bos_token=bos_token,
            sep_token=sep_token,
            pad_token=pad_token,
            **kwargs,
        )

    # hack override
    def get_vocab(self) -> Dict[str, int]:
        return self.get_src_vocab()

    # hack override
    @property
    def vocab_size(self) -> int:
        return self.src_vocab_size

    def moses_punct_norm(self, text, lang):
        if lang not in self.cache_moses_punct_normalizer:
            punct_normalizer = self.sm.MosesPunctNormalizer(lang=lang)
            self.cache_moses_punct_normalizer[lang] = punct_normalizer
        return self.cache_moses_punct_normalizer[lang].normalize(text)

    def moses_tokenize(self, text, lang):
        if lang not in self.cache_moses_tokenizer:
            moses_tokenizer = self.sm.MosesTokenizer(lang=lang)
            self.cache_moses_tokenizer[lang] = moses_tokenizer
        return self.cache_moses_tokenizer[lang].tokenize(
            text, aggressive_dash_splits=True, return_str=False, escape=True
        )

    def moses_detokenize(self, tokens, lang):
        if lang not in self.cache_moses_detokenizer:
            moses_detokenizer = self.sm.MosesDetokenizer(lang=lang)
            self.cache_moses_detokenizer[lang] = moses_detokenizer
        return self.cache_moses_detokenizer[lang].detokenize(tokens)

    def moses_pipeline(self, text, lang):
        text = replace_unicode_punct(text)
        text = self.moses_punct_norm(text, lang)
        text = remove_non_printing_char(text)
        return text

    @property
    def src_vocab_size(self):
        return len(self.encoder)

    @property
    def tgt_vocab_size(self):
        return len(self.decoder)

    def get_src_vocab(self):
        return dict(self.encoder, **self.added_tokens_encoder)

    def get_tgt_vocab(self):
        return dict(self.decoder, **self.added_tokens_decoder)

    def bpe(self, token):
        word = tuple(token[:-1]) + (token[-1] + "</w>",)
        if token in self.cache:
            return self.cache[token]
        pairs = get_pairs(word)

        if not pairs:
            return token + "</w>"

        while True:
            bigram = min(pairs, key=lambda pair: self.bpe_ranks.get(pair, float("inf")))
            if bigram not in self.bpe_ranks:
                break
            first, second = bigram
            new_word = []
            i = 0
            while i < len(word):
                try:
                    j = word.index(first, i)
                except ValueError:
                    new_word.extend(word[i:])
                    break
                else:
                    new_word.extend(word[i:j])
                    i = j

                if word[i] == first and i < len(word) - 1 and word[i + 1] == second:
                    new_word.append(first + second)
                    i += 2
                else:
                    new_word.append(word[i])
                    i += 1
            new_word = tuple(new_word)
            word = new_word
            if len(word) == 1:
                break
            else:
                pairs = get_pairs(word)
        word = " ".join(word)
        if word == "\n  </w>":
            word = "\n</w>"
        self.cache[token] = word
        return word

    def _tokenize(self, text, lang="en", bypass_tokenizer=False):
        """
        Tokenize a string given language code using Moses.

        Details of tokenization:

            - [sacremoses](https://github.com/alvations/sacremoses): port of Moses
            - Install with `pip install sacremoses`

        Args:
            - lang: ISO language code (default = 'en') (string). Languages should belong of the model supported
              languages. However, we don't enforce it.
            - bypass_tokenizer: Allow users to preprocess and tokenize the sentences externally (default = False)
              (bool). If True, we only apply BPE.

        Returns:
            List of tokens.
        """
        # ignore `lang` which is currently isn't explicitly passed in tokenization_utils.py and always results in lang=en
        # if lang != self.src_lang:
        #     raise ValueError(f"Expected lang={self.src_lang}, but got {lang}")
        lang = self.src_lang

        if self.do_lower_case:
            text = text.lower()

        if bypass_tokenizer:
            text = text.split()
        else:
            text = self.moses_pipeline(text, lang=lang)
            text = self.moses_tokenize(text, lang=lang)

        split_tokens = []
        for token in text:
            if token:
                split_tokens.extend(list(self.bpe(token).split(" ")))

        return split_tokens

    def _convert_token_to_id(self, token):
        """Converts a token (str) in an id using the vocab."""
        return self.encoder.get(token, self.encoder.get(self.unk_token))

    def _convert_id_to_token(self, index):
        """Converts an index (integer) in a token (str) using the vocab."""
        return self.decoder.get(index, self.unk_token)

    def convert_tokens_to_string(self, tokens):
        """Converts a sequence of tokens (string) in a single string."""

        # remove BPE
        tokens = [t.replace(" ", "").replace("</w>", " ") for t in tokens]
        tokens = "".join(tokens).split()
        # detokenize
        text = self.moses_detokenize(tokens, self.tgt_lang)
        return text

    def build_inputs_with_special_tokens(
        self, token_ids_0: List[int], token_ids_1: Optional[List[int]] = None
    ) -> List[int]:
        """
        Build model inputs from a sequence or a pair of sequence for sequence classification tasks by concatenating and
        adding special tokens. A FAIRSEQ Transformer sequence has the following format:

        - single sequence: `<s> X </s>`
        - pair of sequences: `<s> A </s> B </s>`

        Args:
            token_ids_0 (`List[int]`):
                List of IDs to which the special tokens will be added.
            token_ids_1 (`List[int]`, *optional*):
                Optional second list of IDs for sequence pairs.

        Returns:
            `List[int]`: List of [input IDs](../glossary#input-ids) with the appropriate special tokens.
        """
        sep = [self.sep_token_id]

        # no bos used in fairseq
        if token_ids_1 is None:
            return token_ids_0 + sep
        return token_ids_0 + sep + token_ids_1 + sep

    def get_special_tokens_mask(
        self, token_ids_0: List[int], token_ids_1: Optional[List[int]] = None, already_has_special_tokens: bool = False
    ) -> List[int]:
        """
        Retrieve sequence ids from a token list that has no special tokens added. This method is called when adding
        special tokens using the tokenizer `prepare_for_model` method.

        Args:
            token_ids_0 (`List[int]`):
                List of IDs.
            token_ids_1 (`List[int]`, *optional*):
                Optional second list of IDs for sequence pairs.
            already_has_special_tokens (`bool`, *optional*, defaults to `False`):
                Whether or not the token list is already formatted with special tokens for the model.

        Returns:
            `List[int]`: A list of integers in the range [0, 1]: 1 for a special token, 0 for a sequence token.
        """

        if already_has_special_tokens:
            return super().get_special_tokens_mask(
                token_ids_0=token_ids_0, token_ids_1=token_ids_1, already_has_special_tokens=True
            )
        # no bos used in fairseq
        if token_ids_1 is not None:
            return ([0] * len(token_ids_0)) + [1] + ([0] * len(token_ids_1)) + [1]
        return ([0] * len(token_ids_0)) + [1]

    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. A FAIRSEQ
        Transformer sequence pair mask has the following format:

        ```
        0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1
        | first sequence    | second sequence |
        ```

        If `token_ids_1` is `None`, this method only returns the first portion of the mask (0s).

        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 [token type IDs](../glossary#token-type-ids) according to the given sequence(s).

        Creates a mask from the two sequences passed to be used in a sequence-pair classification task. An
        FAIRSEQ_TRANSFORMER sequence pair mask has the following format:
        """
        sep = [self.sep_token_id]

        # no bos used in fairseq
        if token_ids_1 is None:
            return len(token_ids_0 + sep) * [0]
        return len(token_ids_0 + sep) * [0] + len(token_ids_1 + sep) * [1]

    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

        src_vocab_file = os.path.join(
            save_directory, (filename_prefix + "-" if filename_prefix else "") + VOCAB_FILES_NAMES["src_vocab_file"]
        )
        tgt_vocab_file = os.path.join(
            save_directory, (filename_prefix + "-" if filename_prefix else "") + VOCAB_FILES_NAMES["tgt_vocab_file"]
        )
        merges_file = os.path.join(
            save_directory, (filename_prefix + "-" if filename_prefix else "") + VOCAB_FILES_NAMES["merges_file"]
        )

        with open(src_vocab_file, "w", encoding="utf-8") as f:
            f.write(json.dumps(self.encoder, indent=2, sort_keys=True, ensure_ascii=False) + "\n")

        with open(tgt_vocab_file, "w", encoding="utf-8") as f:
            tgt_vocab = {v: k for k, v in self.decoder.items()}
            f.write(json.dumps(tgt_vocab, indent=2, sort_keys=True, ensure_ascii=False) + "\n")

        index = 0
        with open(merges_file, "w", encoding="utf-8") as writer:
            for bpe_tokens, token_index in sorted(self.bpe_ranks.items(), key=lambda kv: kv[1]):
                if index != token_index:
                    logger.warning(
                        f"Saving vocabulary to {merges_file}: BPE merge indices are not consecutive."
                        " Please check that the tokenizer is not corrupted!"
                    )
                    index = token_index
                writer.write(" ".join(bpe_tokens) + "\n")
                index += 1

        return src_vocab_file, tgt_vocab_file, merges_file

    def __getstate__(self):
        state = self.__dict__.copy()
        state["sm"] = None
        return state

    def __setstate__(self, d):
        self.__dict__ = d

        try:
            import sacremoses
        except ImportError:
            raise ImportError(
                "You need to install sacremoses to use XLMTokenizer. "
                "See https://pypi.org/project/sacremoses/ for installation."
            )

        self.sm = sacremoses