sglang/.claude/rules/no-getattr-defensive.md

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paths
**/*.py

Don't use getattr / hasattr for defensive access

Over-defensive getattr(obj, "field", default) / hasattr(obj, "field") hide errors and defeat strict type checking. If a field is always present, accessing it defensively is confusing and masks real bugs. Prefer:

1. isinstance for type narrowing — check the type, then access fields directly:

   if (
       isinstance(obj, (TokenizedGenerateReqInput, TokenizedEmbeddingReqInput))
       and obj.mm_inputs
   ):
   

   (see python/sglang/srt/managers/mm_utils.py)

2. Always set the field (to None if needed), then do a None check — the field should always exist, so a None / non-None check is enough:

   obj.field = None   # in __init__ / construction
   ...
   if obj.field is not None:
       ...
   

Bad — server_args always has revision, so getattr is misleading and swallows a real AttributeError if the field is ever renamed:

revision=getattr(server_args, "revision", None),   # BAD
revision=server_args.revision,                     # GOOD

(see python/sglang/srt/managers/template_detection.py)