Improve native object initialization #4798
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mbway
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| @@ -830,12 +830,14 @@ impl<'a> FnSpec<'a> { | |||
| _kwargs: *mut #pyo3_path::ffi::PyObject | |||
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I assume these are named with underscores because sometimes the generated code uses them and sometimes it doesn't?
| ) -> PyResult<*mut ffi::PyObject> { | ||
| // HACK (due to FIXME below): PyBaseObject_Type's tp_new isn't happy with NULL arguments |
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I think there was a misunderstanding here, calling PyBaseObject_Type::tp_new with an empty tuple and NULL kwargs is OK, but the implementation here was passing NULL for both, which is invalid.
| @@ -1,9 +1,60 @@ | |||
| //! Contains initialization utilities for `#[pyclass]`. | |||
| //! | |||
| //! # Background | |||
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although it seems fairly straightforward once compiled like this, it took quite a bit of experimentation to make sure I was getting things correct so I wanted to document my findings somewhere
mbway
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| let obj = tp_new( | ||
| subtype, | ||
| args.as_ptr(), | ||
| kwargs | ||
| .map(|obj| obj.as_ptr()) | ||
| .unwrap_or(std::ptr::null_mut()), | ||
| ); |
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there is a limitation here, where in python a class has to call super(MyClass, cls).__new__(cls, *args, **kwargs) manually so it can choose which options to propagate to the super class. With the current approach the arguments propagate as-is
mbway
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Before this change, classes inheriting the base object was a special case where `object.__new__` is not called, and inheriting from other base classes requires use of the unlimited API. Previously this was not very limiting, but with <PyO3#4678> it will be possible to inherit from native base classes with the limited API and possibly from dynamically imported native base classes which may require `__new__` arguments to reach them.
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Before this change, classes inheriting the base object were constructed by using
TP_ALLOCdirectly, obscuring the intention ofPyNativeTypeInitializer, and inheriting from other base classes requires use of the unlimited API.Previously this was not very limiting, but with #4678 it will be possible to inherit from native base classes with the limited API and possibly from dynamically imported native base classes which may require
__new__arguments to reach them.