Inheritable kw_only for Struct (e.g., kw_only_default=True) #841
Description
Description
Description
Currently, kw_only=True on msgspec.Struct does not inherit to subclasses.
I'm building a pydantic-like wrapper over msgspec, and I want users to define models without repeating kw_only=True:
class BaseModel(Struct, kw_only=True):
...
class User(BaseModel):
age: int = Field(...)
name: str
Today, users must write:
class User(BaseModel, kw_only=True):
age: int = Field(...)
name: strwhich hurts usability.
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Proposal
Add an option like kw_always=True that enables kw_only automatically for subclasses, without needing to re-specify it.
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Why it’s needed
• Easier migration for pydantic users
• Cleaner API
• Avoids complex workarounds (like dynamically generating inner structs)
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Current workaround
I tried subclassing StructMeta but failed.
My only working solution is generating a dynamic InnerStruct at runtime, which complicates type handling, nested structures, and serialization.
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Impact
Supporting kw_only_default =True would significantly improve framework and library development on top of msgspec.
Thanks for considering!