Custom tokenizer with run_mlm script
## Environment info
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- `transformers` version: 4.3.2
- Platform: Linux-5.9.16-1-MANJARO-x86_64-with-glibc2.10
- Python version: 3.8.5
- PyTorch version (GPU?): 1.7.1 (True)
- Tensorflow version (GPU?): not installed (NA)
- Using GPU in script?: Yes
- Using distributed or parallel set-up in script?: NO

### Who can help
@LysandreJik, @n1t0
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Models:

- albert, bert, xlm: @LysandreJik
- blenderbot, bart, marian, pegasus, encoderdecoder,  t5: @patrickvonplaten, @patil-suraj
- longformer, reformer, transfoxl, xlnet: @patrickvonplaten
- fsmt: @stas00
- funnel: @sgugger
- gpt2: @patrickvonplaten, @LysandreJik
- rag: @patrickvonplaten, @lhoestq
- tensorflow: @jplu

Library:

- benchmarks: @patrickvonplaten
- deepspeed: @stas00
- ray/raytune: @richardliaw, @amogkam
- text generation: @patrickvonplaten
- tokenizers: @n1t0, @LysandreJik
- trainer: @sgugger
- pipelines: @LysandreJik

Documentation: @sgugger

HF projects:

- nlp datasets: [different repo](https://github.com/huggingface/nlp)
- rust tokenizers: [different repo](https://github.com/huggingface/tokenizers)

Examples:

- maintained examples (not research project or legacy): @sgugger, @patil-suraj
- research_projects/bert-loses-patience: @JetRunner
- research_projects/distillation: @VictorSanh

 -->

## Information

Model I am using (Bert):

The problem arises when using:
* [ ] the official example scripts: (give details below)
* [ ] my own modified scripts: (give details below)

The tasks I am working on is:
* [ ] my own task or dataset: (give details below)

## To reproduce

Steps to reproduce the behavior:

1. I follow the official link [(https://huggingface.co/docs/tokenizers/python/latest/pipeline.html#example)] to train and save a Bert WordPieceLevel tokenizer on a custom corpus.
2. I use this tokenizer to train a bert model from scratch using the run_mlm script
3.

`python run_mlm.py --output_dir=../Data/model/ --model_type=bert --mlm_probability 0.1 --tokenizer_name=../Data/tokenizer --learning_rate 1e-4 --do_train  --train_file ../Data/corpus.txt  --gradient_accumulation_steps=4 --num_train_epochs 100 --per_gpu_train_batch_size 2 --save_steps 50000 --seed 42 --config_name=../Data/config/ --line_by_line --do_eval --max_seq_length=8 --logging_steps 5000 --validation_split_percentage 20 --save_steps 50000  --save_total_limit 10`



  





    from tokenizers import Tokenizer
    from tokenizers.models import WordPiece
    from tokenizers.pre_tokenizers import Whitespace
    from tokenizers import normalizers
    from tokenizers.normalizers import NFD, StripAccents
    from tokenizers.processors import TemplateProcessing
    from tokenizers.trainers import WordPieceTrainer
    vocab_file = '../Data/tokenizer/config.json'
    corpus_file = '../Data/corpus.txt'
    df = pd.read_csv(corpus_file)
    bert_tokenizer = Tokenizer(WordPiece(unk_token="[UNK]"))
    bert_tokenizer.normalizer = normalizers.Sequence([NFD(), StripAccents()])
    bert_tokenizer.pre_tokenizer = Whitespace()
    bert_tokenizer.post_processor = TemplateProcessing(
        single="[CLS] $A [SEP]",
        pair="[CLS] $A [SEP] $B:1 [SEP]:1",
        special_tokens=[("[CLS]", 1),("[SEP]", 2),],)
    trainer = WordPieceTrainer(vocab_size=25000,min_frequency=3,special_tokens=["[UNK]", "[CLS]", "[SEP]", "[PAD]", "[MASK]"])
    bert_tokenizer.train_from_iterator(df.query_text.to_list(),trainer)
    bert_tokenizer.save(vocab_file)

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My training configuration is as follows
`  "architectures": [
    "BertForMaskedLM"
  ],
  "attention_probs_dropout_prob": 0.1,
  "gradient_checkpointing": false,
  "hidden_act": "gelu",
  "hidden_dropout_prob": 0.1,
  "hidden_size": 128,
  "initializer_range": 0.02,
  "intermediate_size": 256,
  "layer_norm_eps": 1e-12,
  "max_position_embeddings": 1536,
  "model_type": "bert",
  "num_attention_heads": 4,
  "num_hidden_layers": 4,
  "pad_token_id": 0,
  "position_embedding_type": "absolute",
  "transformers_version": "4.3.2",
  "type_vocab_size": 2,
  "use_cache": true,
  "vocab_size": 25000
`
## Expected behavior

<!-- A clear and concise description of what you would expect to happen. -->
I am getting the error

 ` loading configuration file ../Data/tokenizer/config.json
Traceback (most recent call last):
  File "run_mlm.py", line 457, in <module>
    main()
  File "run_mlm.py", line 276, in main
    tokenizer = AutoTokenizer.from_pretrained(model_args.tokenizer_name, **tokenizer_kwargs)
  File ".../lib/python3.8/site-packages/transformers/models/auto/tokenization_auto.py", line 362, in from_pretrained
    config = AutoConfig.from_pretrained(pretrained_model_name_or_path, **kwargs)
  File ".../lib/python3.8/site-packages/transformers/models/auto/configuration_auto.py", line 379, in from_pretrained
    raise ValueError(
ValueError: Unrecognized model in ../Data/tokenizer. Should have a `model_type` key in its config.json, or contain one of the following strings in its name: wav2vec2, convbert, led, blenderbot-small, retribert, mt5, t5, mobilebert, distilbert, albert, bert-generation, camembert, xlm-roberta, pegasus, marian, mbart, mpnet, bart, blenderbot, reformer, longformer, roberta, deberta, flaubert, fsmt, squeezebert, bert, openai-gpt, gpt2, transfo-xl, xlnet, xlm-prophetnet, prophetnet, xlm, ctrl, electra, encoder-decoder, funnel, lxmert, dpr, layoutlm, rag, tapas`
Hi! The issue here is that the `AutoTokenizer` has no idea what is the type of your tokenizer: it's looking for the `model_type` specified in the `config.json`, but it seems it cannot find it.

Could you show us the results of `ls ../Data/tokenizer/`, and if the file `config.json` is in it, could you show us the exact content of the JSON file?

Thanks a lot!<|||||>I am expecting the config.json and vocabulary files to be saved by running `bert_tokenizer.save(vocab_file)` (Please check the attached code). But unfortunately it saves a json file containing only the vocabulary.  I tried the function `bert_tokenizer.save_model`, but got an error saying Tokenizer don't have such a function. So there is no configuration files. But only a vocabulary json file. If I give a directory path as input to  `bert_tokenizer.save`, it  gives me error `Exception: Is a directory (os error 21)`.<|||||>The `bert_tokenizer.save(vocab_file)` method does not save the configuration as the configuration is linked to the model. It is unfortunately currently impossible to use the `AutoTokenizer` without having the model `config.json` in the same folder, which is a hard limitation of the `AutoTokenizer`.

We are aware of this limitation and it is part of the immediate roadmap. Expect a change in the coming weeks related to that issue.

Thank you for your understanding.<|||||>This issue has been automatically marked as stale because it has not had recent activity. If you think this still needs to be addressed please comment on this thread.

Please note that issues that do not follow the [contributing guidelines](https://github.com/huggingface/transformers/blob/master/CONTRIBUTING.md) are likely to be ignored.<|||||>Hi @LysandreJik! Has there been any change on this subject?<|||||>There hasn't been any change - but we've been freeing some time to work on this subject. I would expect this to be resolved in 2 or 3 weeks.<|||||>Awesome, thanks a lot for your reply :) <|||||>I also encountered this problem, how to solve it<|||||>Using a recent version of the library should now work for these use-cases.

Could you try using the `master` branch to see if it fixes your issue? You should use it to both save your tokenizer, as well as to load it in the script. If it doesn't work, please provide the code you're using as well as the full stack trace. Thank you!