[Core] Support dynamically loading Lora adapter from HuggingFace (#6234)

Co-authored-by: Antoni Baum <antoni.baum@protonmail.com>

tests/lora/test_utils.py

@@ -1,9 +1,12 @@
 from collections import OrderedDict
+from unittest.mock import patch
 
 import pytest
+from huggingface_hub.utils import HfHubHTTPError
 from torch import nn
 
-from vllm.lora.utils import parse_fine_tuned_lora_name, replace_submodule
+from vllm.lora.utils import (get_adapter_absolute_path,
+                             parse_fine_tuned_lora_name, replace_submodule)
 from vllm.utils import LRUCache
 
 
@@ -182,3 +185,55 @@ def test_lru_cache():
     assert 2 in cache
     assert 4 in cache
     assert 6 in cache
+
+
+# Unit tests for get_adapter_absolute_path
+@patch('os.path.isabs')
+def test_get_adapter_absolute_path_absolute(mock_isabs):
+    path = '/absolute/path/to/lora'
+    mock_isabs.return_value = True
+    assert get_adapter_absolute_path(path) == path
+
+
+@patch('os.path.expanduser')
+def test_get_adapter_absolute_path_expanduser(mock_expanduser):
+    # Path with ~ that needs to be expanded
+    path = '~/relative/path/to/lora'
+    absolute_path = '/home/user/relative/path/to/lora'
+    mock_expanduser.return_value = absolute_path
+    assert get_adapter_absolute_path(path) == absolute_path
+
+
+@patch('os.path.exists')
+@patch('os.path.abspath')
+def test_get_adapter_absolute_path_local_existing(mock_abspath, mock_exist):
+    # Relative path that exists locally
+    path = 'relative/path/to/lora'
+    absolute_path = '/absolute/path/to/lora'
+    mock_exist.return_value = True
+    mock_abspath.return_value = absolute_path
+    assert get_adapter_absolute_path(path) == absolute_path
+
+
+@patch('huggingface_hub.snapshot_download')
+@patch('os.path.exists')
+def test_get_adapter_absolute_path_huggingface(mock_exist,
+                                               mock_snapshot_download):
+    # Hugging Face model identifier
+    path = 'org/repo'
+    absolute_path = '/mock/snapshot/path'
+    mock_exist.return_value = False
+    mock_snapshot_download.return_value = absolute_path
+    assert get_adapter_absolute_path(path) == absolute_path
+
+
+@patch('huggingface_hub.snapshot_download')
+@patch('os.path.exists')
+def test_get_adapter_absolute_path_huggingface_error(mock_exist,
+                                                     mock_snapshot_download):
+    # Hugging Face model identifier with download error
+    path = 'org/repo'
+    mock_exist.return_value = False
+    mock_snapshot_download.side_effect = HfHubHTTPError(
+        "failed to query model info")
+    assert get_adapter_absolute_path(path) == path