Loading LORA weights with `load_lora_weights` do not respect `HF_HUB_OFFLINE` / `local_file_only`

[Wauplin]

First reported by @rvorias in huggingface/huggingface_hub#1893 (comment).

TL;DR: Loading lora weights on a pipeline makes a call to the Hub even when HF_HUB_OFFLINE=1 is set as environment variable (or local_file_only=True is passed as parameter), which is not expected.

This seems to be due to the _best_guess_weight_name method that try to guess which file to load when the LoRA filename is not provided. It makes a call to model_info to check which files exist on the Hub repo.

pipeline.load_lora_weights(
  "latent-consistency/lcm-lora-sdxl",
  adapter_name="lcm",
  cache_dir=cache_dir,
  local_files_only=True,
)

Suggestions:

• raise an error if offline mode => "hey you should pass a filename"
• check local cache if offline mode => try to guess based on that locally saved files?

[sayakpaul]

Maybe it's better to be explicit here so, I would prefer the first option.

[Wauplin]

Agree on raising an explicit error while the problem is not solved but it would be good to be able to load lora weights while being offline, no? I think it just requires to list the local files (os.listdir(snapshot_path)) instead of listing files from the Hub.

And I'll open an issue in huggingface_hub to raise explicit error in all method of HfApi if HF_HUB_OFFLINE=1 (currently only the case for download methods).

[sayakpaul]

I think it just requires to list the local files (os.listdir(snapshot_path)) instead of listing files from the Hub.

Hmm, so when local_files_only=True we do os.listdir(...), yeah? Yeah, that makes sense too.

[Wauplin]

I created huggingface/huggingface_hub#1899 in huggingface_hub to raise an explicit error if someone tries to call the Hub with HF_HUB_OFFLINE=1. It will make it more obvious to the user what happens.
diffusers will have to deal with OfflineModeIsEnabled exception the same way it deals with local_files_only=True. Instead of catching the error, another possibility is to look at the huggingface_hub.constant.HF_HUB_OFFLINE constant directly (i.e. have a condition if local_files_only or constants.HF_HUB_OFFLINE: ....

[sayakpaul]

@Wauplin thanks for your inputs. I will take a closer look soon and open a PR asking for your review.