Fix underscores in dict keys passed via CLI (#19030)

Signed-off-by: Harry Mellor <19981378+hmellor@users.noreply.github.com>

tests/test_utils.py

@@ -259,11 +259,18 @@ def test_dict_args(parser):
         "--model-name=something.something",
         "--hf-overrides.key1",
         "val1",
+        # Test nesting
         "--hf-overrides.key2.key3",
         "val2",
         "--hf-overrides.key2.key4",
         "val3",
+        # Test = sign
         "--hf-overrides.key5=val4",
+        # Test underscore to dash conversion
+        "--hf_overrides.key_6",
+        "val5",
+        "--hf_overrides.key-7.key_8",
+        "val6",
     ]
     parsed_args = parser.parse_args(args)
     assert parsed_args.model_name == "something.something"
@@ -274,6 +281,10 @@ def test_dict_args(parser):
             "key4": "val3",
         },
         "key5": "val4",
+        "key_6": "val5",
+        "key-7": {
+            "key_8": "val6",
+        },
     }
 
 

vllm/utils.py

@@ -1456,17 +1456,24 @@ class FlexibleArgumentParser(ArgumentParser):
         if '--config' in args:
             args = self._pull_args_from_config(args)
 
+        def repl(match: re.Match) -> str:
+            """Replaces underscores with dashes in the matched string."""
+            return match.group(0).replace("_", "-")
+
+        # Everything between the first -- and the first .
+        pattern = re.compile(r"(?<=--)[^\.]*")
+
         # Convert underscores to dashes and vice versa in argument names
         processed_args = []
         for arg in args:
             if arg.startswith('--'):
                 if '=' in arg:
                     key, value = arg.split('=', 1)
-                    key = '--' + key[len('--'):].replace('_', '-')
+                    key = pattern.sub(repl, key, count=1)
                     processed_args.append(f'{key}={value}')
                 else:
-                    processed_args.append('--' +
-                                          arg[len('--'):].replace('_', '-'))
+                    key = pattern.sub(repl, arg, count=1)
+                    processed_args.append(key)
             elif arg.startswith('-O') and arg != '-O' and len(arg) == 2:
                 # allow -O flag to be used without space, e.g. -O3
                 processed_args.append('-O')