[Bugfix] Fix filepath resolution for model with subdir and GLM-Image generation

[yuanheng-zhao]

PLEASE FILL IN THE PR DESCRIPTION HERE ENSURING ALL CHECKLIST ITEMS (AT THE BOTTOM) HAVE BEEN CONSIDERED.

Purpose

Resolves #1608

This PR fixed the file path resolution in stage util for models which have model_subdir or tokenizer_subdir, and so that enabled GLM-Image generation with model ID.

Test Plan

Offline generation of GLM-Image

# Under vLLM-Omni repo
cd examples/offline_inference/glm_image
python end2end.py \
    --config-path ../../../vllm_omni/model_executor/stage_configs/glm_image.yaml \
    --prompt "A beautiful sunset over the ocean with sailing boats" \
    --height 1024 \
    --width 1024 \
    --output output_t2i.png

*Note: in order to run GLM-Image, we have to install the latest transformers and diffusers in editable way in the virtual env.

Test Result

1. Without the changes on _resolve_model_tokenizer_paths for model with subdir, the following error happened:

[Stage-0] ERROR 03-02 14:14:43 [repo_utils.py:47] Error retrieving file list: Repo id must be in the form 'repo_name' or 'namespace/repo_name': 'zai-org/GLM-Image/vision_language_encoder'. Use `repo_type` argument if needed., retrying 1 of 2
[Stage-1] INFO 03-02 14:14:43 [omni_stage.py:79] NVML process-scoped memory available and PID host is available — concurrent init is safe, skipping locks
[Stage-0] ERROR 03-02 14:14:45 [repo_utils.py:45] Error retrieving file list: Repo id must be in the form 'repo_name' or 'namespace/repo_name': 'zai-org/GLM-Image/vision_language_encoder'. Use `repo_type` argument if needed.
[Stage-0] ERROR 03-02 14:14:45 [repo_utils.py:110] Error retrieving file list. Please ensure your `model_name_or_path``repo_type`, `token` and `revision` arguments are correctly set. Returning an empty list.
Process SpawnProcess-1:
Traceback (most recent call last):
  File "/ws/repos/vllm-project/vllm-omni/.venv/lib/python3.12/site-packages/vllm/transformers_utils/config.py", line 578, in get_config
    elif (_is_gguf and not _is_remote_gguf) or file_or_path_exists(
                                               ^^^^^^^^^^^^^^^^^^^^
  File "/ws/repos/vllm-project/vllm-omni/.venv/lib/python3.12/site-packages/vllm/transformers_utils/repo_utils.py", line 190, in file_or_path_exists
    cached_filepath = try_to_load_from_cache(
                      ^^^^^^^^^^^^^^^^^^^^^^^
  File "/ws/repos/vllm-project/vllm-omni/.venv/lib/python3.12/site-packages/huggingface_hub/utils/_validators.py", line 85, in _inner_fn
    validate_repo_id(arg_value)
  File "/ws/repos/vllm-project/vllm-omni/.venv/lib/python3.12/site-packages/huggingface_hub/utils/_validators.py", line 129, in validate_repo_id
    raise HFValidationError(
huggingface_hub.errors.HFValidationError: Repo id must be in the form 'repo_name' or 'namespace/repo_name': 'zai-org/GLM-Image/vision_language_encoder'. Use `repo_type` argument if needed.

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/ws/repos/vllm-project/vllm-omni/vllm_omni/entrypoints/utils.py", line 191, in resolve_model_config_path
    hf_config = get_config(model, trust_remote_code=True)
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/ws/repos/vllm-project/vllm-omni/.venv/lib/python3.12/site-packages/vllm/transformers_utils/config.py", line 619, in get_config
    raise ValueError(error_message) from e
ValueError: Invalid repository ID or local directory specified: 'zai-org/GLM-Image/vision_language_encoder'.
Please verify the following requirements:
1. Provide a valid Hugging Face repository ID.
3. Specify a local directory that contains a recognized configuration file.
   - For Hugging Face models: ensure the presence of a 'config.json'.
   - For Mistral models: ensure the presence of a 'params.json'.

2. Running with the fix, the image can be successfully generated:

---

Essential Elements of an Effective PR Description Checklist

• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
• The test plan. Please provide the test scripts & test commands. Please state the reasons if your codes don't require additional test scripts. For test file guidelines, please check the test style doc
• The test results. Please paste the results comparison before and after, or the e2e results.
• (Optional) The necessary documentation update, such as updating supported_models.md and examples for a new model. Please run mkdocs serve to sync the documentation editions to ./docs.
• (Optional) Release notes update. If your change is user-facing, please update the release notes draft.

BEFORE SUBMITTING, PLEASE READ https://github.com/vllm-project/vllm-omni/blob/main/CONTRIBUTING.md (anything written below this line will be removed by GitHub Actions)

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[hsliuustc0106]

Review Summary

This bugfix addresses a real issue with HF Hub model IDs and subdirectories, but has a few concerns that should be addressed.

Critical Issues

1. Missing regression test - No test coverage for the new path resolution logic
2. Broad exception handling - Masks root cause of failures
3. Requires pre-cached models - local_files_only=True will fail for first-time downloads

Minor Issues

4. Inconsistent example in README (one command still shows --model-path)

Please see inline comments for details.