Expose missing mappings (see #3415)

examples/run_language_modeling.py

@@ -38,7 +38,6 @@ from torch.utils.data.distributed import DistributedSampler
 from tqdm import tqdm, trange
 
 from transformers import (
-    CONFIG_MAPPING,
     MODEL_WITH_LM_HEAD_MAPPING,
     WEIGHTS_NAME,
     AdamW,
@@ -679,7 +678,12 @@ def main():
     elif args.model_name_or_path:
         config = AutoConfig.from_pretrained(args.model_name_or_path, cache_dir=args.cache_dir)
     else:
-        config = CONFIG_MAPPING[args.model_type]()
+        # When we release a pip version exposing CONFIG_MAPPING,
+        # we can do `config = CONFIG_MAPPING[args.model_type]()`.
+        raise ValueError(
+            "You are instantiating a new config instance from scratch. This is not supported, but you can do it from another script, save it,"
+            "and load it from here, using --config_name"
+        )
 
     if args.tokenizer_name:
         tokenizer = AutoTokenizer.from_pretrained(args.tokenizer_name, cache_dir=args.cache_dir)
@@ -687,8 +691,8 @@ def main():
         tokenizer = AutoTokenizer.from_pretrained(args.model_name_or_path, cache_dir=args.cache_dir)
     else:
         raise ValueError(
-            "You are instantiating a new {} tokenizer. This is not supported, but you can do it from another script, save it,"
-            "and load it from here, using --tokenizer_name".format(AutoTokenizer.__name__)
+            "You are instantiating a new tokenizer from scratch. This is not supported, but you can do it from another script, save it,"
+            "and load it from here, using --tokenizer_name"
         )
 
     if args.block_size <= 0:

src/transformers/__init__.py

@@ -32,7 +32,7 @@ from .benchmark_utils import (
     stop_memory_tracing,
 )
 from .configuration_albert import ALBERT_PRETRAINED_CONFIG_ARCHIVE_MAP, AlbertConfig
-from .configuration_auto import ALL_PRETRAINED_CONFIG_ARCHIVE_MAP, AutoConfig
+from .configuration_auto import ALL_PRETRAINED_CONFIG_ARCHIVE_MAP, CONFIG_MAPPING, AutoConfig
 from .configuration_bart import BartConfig
 from .configuration_bert import BERT_PRETRAINED_CONFIG_ARCHIVE_MAP, BertConfig
 from .configuration_camembert import CAMEMBERT_PRETRAINED_CONFIG_ARCHIVE_MAP, CamembertConfig
@@ -119,7 +119,7 @@ from .pipelines import (
     pipeline,
 )
 from .tokenization_albert import AlbertTokenizer
-from .tokenization_auto import AutoTokenizer
+from .tokenization_auto import TOKENIZER_MAPPING, AutoTokenizer
 from .tokenization_bart import BartTokenizer
 from .tokenization_bert import BasicTokenizer, BertTokenizer, BertTokenizerFast, WordpieceTokenizer
 from .tokenization_bert_japanese import BertJapaneseTokenizer, CharacterTokenizer, MecabTokenizer