stubgen drops default values for function arguments #13238

Bug Report

I have a file with some types defined (that I can't modify), and want to create a stub for this file so that I can fill out the remainder of the types.

So I run stubgen, and it creates draft stubs, but all the default parameter values that had been defined are lost.

.py source file:

def hash_pandas_object(
    obj: Index | DataFrame | Series,
    index: bool = True,
    encoding: str = "utf8",
    hash_key: str | None = _default_hash_key,
    categorize: bool = True,
) -> Series:

Generated .pyi file

def hash_pandas_object(
    obj: Union[Index, DataFrame, Series],
    index: bool = ...,
    encoding: str = ...,
    hash_key: Union[str, None] = ...,
    categorize: bool = ...,
) -> Series: ...

I understand that typically these default values are considered implementation code and don't 'belong' in a stub file, but nonetheless they are quite useful to me. For example, with a stub file present, IntelliJ will show me the signature from the stub, but now I've lost the information of what the default encoding is:

It would be nice to at least have an (opt-in) option when generating stubs to keep these default values.