Warning for invalid options without "--with_prior_preservation" (#1065)

* Make errors for invalid options without "--with_prior_preservation"

* Make --instance_prompt required

* Removed needless check because --instance_data_dir is marked with required

* Updated messages

* Use logger.warning instead of raise errors
Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>

examples/dreambooth/train_dreambooth.py

@@ -66,6 +66,7 @@ def parse_args(input_args=None):
         "--instance_prompt",
         type=str,
         default=None,
+        required=True,
         help="The prompt with identifier specifying the instance",
     )
     parser.add_argument(
@@ -205,14 +206,16 @@ def parse_args(input_args=None):
     if env_local_rank != -1 and env_local_rank != args.local_rank:
         args.local_rank = env_local_rank
 
-    if args.instance_data_dir is None:
-        raise ValueError("You must specify a train data directory.")
-
     if args.with_prior_preservation:
         if args.class_data_dir is None:
             raise ValueError("You must specify a data directory for class images.")
         if args.class_prompt is None:
             raise ValueError("You must specify prompt for class images.")
+    else:
+        if args.class_data_dir is not None:
+            logger.warning("You need not use --class_data_dir without --with_prior_preservation.")
+        if args.class_prompt is not None:
+            logger.warning("You need not use --class_prompt without --with_prior_preservation.")
 
     return args