Environment info

• transformers version: 3.4.0
• Platform: Linux-5.4.0-52-generic-x86_64-with-debian-buster-sid
• Python version: 3.7.6
• PyTorch version (GPU?): 1.5.1 (False)
• Tensorflow version (GPU?): not installed (NA)
• Using GPU in script?: No
• Using distributed or parallel set-up in script?: No

Who can help

@mfuntowicz

Information

The do_lower_case property of BertTokenizer is not correctly restored after saving / loading.

To reproduce

from transformers import BertTokenizer

tokenizer = BertTokenizer.from_pretrained("bert-base-cased")
print(tokenizer.do_lower_case)

tokenizer.save_pretrained("debug_tokenizer")
tokenizer_loaded = BertTokenizer.from_pretrained("debug_tokenizer")
print(tokenizer_loaded.do_lower_case)

returns

False
True

Expected behavior

Same object attributes after saving / loading