# pyproto.rs - source
Source of the Rust file `/home/runner/.cargo/registry/src/github.com-1ecc6299db9ec823/pyo3-macros-backend-0.13.2/src/pyproto.rs`.
Keywords: rust, rustlang, rust-lang

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    // Copyright (c) 2017-present PyO3 Project and Contributors

    use crate::defs;
    use crate::method::{FnSpec, FnType};
    use crate::proto_method::impl_method_proto;
    use crate::pymethod;
    use proc_macro2::{Span, TokenStream};
    use quote::quote;
    use quote::ToTokens;
    use std::collections::HashSet;
    use syn::spanned::Spanned;

    pub fn build_py_proto(ast: &mut syn::ItemImpl) -> syn::Result<TokenStream> {
        let (path, proto) = if let Some((_, path, _)) = &mut ast.trait_ {
            let proto = match path.segments.last() {
                Some(segment) if segment.ident == "PyObjectProtocol" => &defs::OBJECT,
                Some(segment) if segment.ident == "PyAsyncProtocol" => &defs::ASYNC,
                Some(segment) if segment.ident == "PyMappingProtocol" => &defs::MAPPING,
                Some(segment) if segment.ident == "PyIterProtocol" => &defs::ITER,
                Some(segment) if segment.ident == "PyContextProtocol" => &defs::CONTEXT,
                Some(segment) if segment.ident == "PySequenceProtocol" => &defs::SEQ,
                Some(segment) if segment.ident == "PyNumberProtocol" => &defs::NUM,
                Some(segment) if segment.ident == "PyDescrProtocol" => &defs::DESCR,
                Some(segment) if segment.ident == "PyBufferProtocol" => &defs::BUFFER,
                Some(segment) if segment.ident == "PyGCProtocol" => &defs::GC,
                _ => bail_spanned!(path.span() => "unrecognised trait for #[pyproto]"),
            };
            (path, proto)
        } else {
            bail_spanned!(
                ast.span() => "#[pyproto] can only be used with protocol trait implementations"
            );
        };

        let tokens = impl_proto_impl(&ast.self_ty, &mut ast.items, proto)?;

        // attach lifetime
        let mut seg = path.segments.pop().unwrap().into_value();
        seg.arguments = syn::PathArguments::AngleBracketed(syn::parse_quote! {<'p>});
        path.segments.push(seg);
        ast.generics.params = syn::parse_quote! {'p};
        Ok(tokens)
    }

    fn impl_proto_impl(
        ty: &syn::Type,
        impls: &mut Vec<syn::ImplItem>,
        proto: &defs::Proto,
    ) -> syn::Result<TokenStream> {
        let mut trait_impls = TokenStream::new();
        let mut py_methods = Vec::new();
        let mut method_names = HashSet::new();
        let module = proto.module();

        for iimpl in impls.iter_mut() {
            if let syn::ImplItem::Method(met) = iimpl {
                // impl Py~Protocol<'p> { type = ... }
                if let Some(m) = proto.get_proto(&met.sig.ident) {
                    impl_method_proto(ty, &mut met.sig, &module, m)?.to_tokens(&mut trait_impls);
                    // Insert the method to the HashSet
                    method_names.insert(met.sig.ident.to_string());
                }
                // Add non-slot methods to inventory like `#[pymethods]`
                if let Some(m) = proto.get_method(&met.sig.ident) {
                    let name = &met.sig.ident;
                    let fn_spec = FnSpec::parse(&met.sig, &mut met.attrs, false)?;

                    let method = if let FnType::Fn(self_ty) = &fn_spec.tp {
                        pymethod::impl_proto_wrap(ty, &fn_spec, &self_ty)
                    } else {
                        bail_spanned!(
                            met.sig.span() => "expected method with receiver for #[pyproto] method"
                        );
                    };

                    let coexist = if m.can_coexist {
                        // We need METH_COEXIST here to prevent __add__  from overriding __radd__
                        quote!(pyo3::ffi::METH_COEXIST)
                    } else {
                        quote!(0)
                    };
                    // TODO(kngwyu): Set ml_doc
                    py_methods.push(quote! {
                        pyo3::class::PyMethodDefType::Method({
                            #method
                            pyo3::class::PyMethodDef::cfunction_with_keywords(
                                concat!(stringify!(#name), "\0"),
                                __wrap,
                                #coexist,
                                "\0"
                            )
                        })
                    });
                }
            }
        }
        let normal_methods = submit_normal_methods(py_methods, ty);
        let protocol_methods = impl_proto_methods(method_names, ty, proto);
        Ok(quote! {
            #trait_impls
            #normal_methods
            #protocol_methods
        })
    }

    fn submit_normal_methods(py_methods: Vec<TokenStream>, ty: &syn::Type) -> TokenStream {
        if py_methods.is_empty() {
            return quote! {};
        }
        quote! {
            pyo3::inventory::submit! {
                #![crate = pyo3] {
                    type Inventory = <#ty as pyo3::class::methods::HasMethodsInventory>::Methods;
                    <Inventory as pyo3::class::methods::PyMethodsInventory>::new(vec![#(#py_methods),*])
                }
            }
        }
    }

    fn impl_proto_methods(
        method_names: HashSet<String>,
        ty: &syn::Type,
        proto: &defs::Proto,
    ) -> TokenStream {
        if proto.slots_trait.is_empty() {
            return TokenStream::default();
        }

        let module = proto.module();
        let slots_trait = syn::Ident::new(proto.slots_trait, Span::call_site());
        let slots_trait_slots = syn::Ident::new(proto.slots_trait_slots, Span::call_site());

        let mut maybe_buffer_methods = None;
        if proto.name == "Buffer" {
            // On Python 3.9 we have to use PyBufferProcs to set buffer slots.
            // For now we emit this always for buffer methods, even on 3.9+.
            // Maybe in the future we can access Py_3_9 here and define it.
            maybe_buffer_methods = Some(quote! {
                impl pyo3::class::proto_methods::PyBufferProtocolProcs<#ty>
                    for pyo3::class::proto_methods::PyClassProtocols<#ty>
                {
                    fn buffer_procs(
                        self
                    ) -> Option<&'static pyo3::class::proto_methods::PyBufferProcs> {
                        static PROCS: pyo3::class::proto_methods::PyBufferProcs
                            = pyo3::class::proto_methods::PyBufferProcs {
                                bf_getbuffer: Some(pyo3::class::buffer::getbuffer::<#ty>),
                                bf_releasebuffer: Some(pyo3::class::buffer::releasebuffer::<#ty>),
                            };
                        Some(&PROCS)
                    }
                }
            });
        }

        let mut tokens = proto
            .slot_defs(method_names)
            .map(|def| {
                let slot = syn::Ident::new(def.slot, Span::call_site());
                let slot_impl = syn::Ident::new(def.slot_impl, Span::call_site());
                quote! {{
                    pyo3::ffi::PyType_Slot {
                        slot: pyo3::ffi::#slot,
                        pfunc: #module::#slot_impl::<#ty> as _
                    }
                }}
            })
            .peekable();

        if tokens.peek().is_none() {
            return TokenStream::default();
        }

        quote! {
            #maybe_buffer_methods

            impl pyo3::class::proto_methods::#slots_trait<#ty>
                for pyo3::class::proto_methods::PyClassProtocols<#ty>
            {
                fn #slots_trait_slots(self) -> &'static [pyo3::ffi::PyType_Slot] {
                    &[#(#tokens),*]
                }
            }
        }
    }