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

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

    use crate::method::{FnType, SelfType};
    use crate::pymethod::{
        impl_py_getter_def, impl_py_setter_def, impl_wrap_getter, impl_wrap_setter, PropertyType,
    };
    use crate::utils;
    use proc_macro2::{Span, TokenStream};
    use quote::quote;
    use syn::ext::IdentExt;
    use syn::parse::{Parse, ParseStream};
    use syn::punctuated::Punctuated;
    use syn::{parse_quote, spanned::Spanned, Expr, Token};

    /// The parsed arguments of the pyclass macro
    pub struct PyClassArgs {
        pub freelist: Option<syn::Expr>,
        pub name: Option<syn::Ident>,
        pub flags: Vec<syn::Expr>,
        pub base: syn::TypePath,
        pub has_extends: bool,
        pub has_unsendable: bool,
        pub module: Option<syn::LitStr>,
    }

    impl Parse for PyClassArgs {
        fn parse(input: ParseStream) -> syn::parse::Result<Self> {
            let mut slf = PyClassArgs::default();

            let vars = Punctuated::<Expr, Token![,]>::parse_terminated(input)?;
            for expr in vars {
                slf.add_expr(&expr)?;
            }
            Ok(slf)
        }
    }

    impl Default for PyClassArgs {
        fn default() -> Self {
            PyClassArgs {
                freelist: None,
                name: None,
                module: None,
                // We need the 0 as value for the constant we're later building using quote for when there
                // are no other flags
                flags: vec![parse_quote! { 0 }],
                base: parse_quote! { pyo3::PyAny },
                has_extends: false,
                has_unsendable: false,
            }
        }
    }

    impl PyClassArgs {
        /// Adda single expression from the comma separated list in the attribute, which is
        /// either a single word or an assignment expression
        fn add_expr(&mut self, expr: &Expr) -> syn::parse::Result<()> {
            match expr {
                syn::Expr::Path(exp) if exp.path.segments.len() == 1 => self.add_path(exp),
                syn::Expr::Assign(assign) => self.add_assign(assign),
                _ => bail_spanned!(expr.span() => "failed to parse arguments"),
            }
        }

        /// Match a key/value flag
        fn add_assign(&mut self, assign: &syn::ExprAssign) -> syn::Result<()> {
            let syn::ExprAssign { left, right, .. } = assign;
            let key = match &**left {
                syn::Expr::Path(exp) if exp.path.segments.len() == 1 => {
                    exp.path.segments.first().unwrap().ident.to_string()
                }
                _ => bail_spanned!(assign.span() => "failed to parse arguments"),
            };

            macro_rules! expected {
                ($expected: literal) => {
                    expected!($expected, right.span())
                };
                ($expected: literal, $span: expr) => {
                    bail_spanned!($span => concat!("expected ", $expected));
                };
            }

            match key.as_str() {
                "freelist" => {
                    // We allow arbitrary expressions here so you can e.g. use `8*64`
                    self.freelist = Some(syn::Expr::clone(right));
                }
                "name" => match &**right {
                    syn::Expr::Lit(syn::ExprLit {
                        lit: syn::Lit::Str(lit),
                        ..
                    }) => {
                        self.name = Some(lit.parse().map_err(|_| {
                            err_spanned!(
                                    lit.span() => "expected a single identifier in double-quotes")
                        })?);
                    }
                    syn::Expr::Path(exp) if exp.path.segments.len() == 1 => {
                        bail_spanned!(
                            exp.span() => format!(
                                "since PyO3 0.13 a pyclass name should be in double-quotes, \
                                e.g. \"{}\"",
                                exp.path.get_ident().expect("path has 1 segment")
                            )
                        );
                    }
                    _ => expected!("type name (e.g. \"Name\")"),
                },
                "extends" => match &**right {
                    syn::Expr::Path(exp) => {
                        self.base = syn::TypePath {
                            path: exp.path.clone(),
                            qself: None,
                        };
                        self.has_extends = true;
                    }
                    _ => expected!("type path (e.g., my_mod::BaseClass)"),
                },
                "module" => match &**right {
                    syn::Expr::Lit(syn::ExprLit {
                        lit: syn::Lit::Str(lit),
                        ..
                    }) => {
                        self.module = Some(lit.clone());
                    }
                    _ => expected!(r#"string literal (e.g., "my_mod")"#),
                },
                _ => expected!("one of freelist/name/extends/module", left.span()),
            };

            Ok(())
        }

        /// Match a single flag
        fn add_path(&mut self, exp: &syn::ExprPath) -> syn::Result<()> {
            let flag = exp.path.segments.first().unwrap().ident.to_string();
            let mut push_flag = |flag| {
                self.flags.push(syn::Expr::Path(flag));
            };
            match flag.as_str() {
                "gc" => push_flag(parse_quote! {pyo3::type_flags::GC}),
                "weakref" => push_flag(parse_quote! {pyo3::type_flags::WEAKREF}),
                "subclass" => push_flag(parse_quote! {pyo3::type_flags::BASETYPE}),
                "dict" => push_flag(parse_quote! {pyo3::type_flags::DICT}),
                "unsendable" => {
                    self.has_unsendable = true;
                }
                _ => bail_spanned!(
                    exp.path.span() => "expected one of gc/weakref/subclass/dict/unsendable"
                ),
            };
            Ok(())
        }
    }

    pub fn build_py_class(class: &mut syn::ItemStruct, attr: &PyClassArgs) -> syn::Result<TokenStream> {
        let text_signature = utils::parse_text_signature_attrs(
            &mut class.attrs,
            &get_class_python_name(&class.ident, attr),
        )?;
        let doc = utils::get_doc(&class.attrs, text_signature, true)?;
        let mut descriptors = Vec::new();

        ensure_spanned!(
            class.generics.params.is_empty(),
            class.generics.span() => "#[pyclass] cannot have generic parameters"
        );

        if let syn::Fields::Named(fields) = &mut class.fields {
            for field in fields.named.iter_mut() {
                let field_descs = parse_descriptors(field)?;
                if !field_descs.is_empty() {
                    descriptors.push((field.clone(), field_descs));
                }
            }
        } else {
            bail_spanned!(class.fields.span() => "#[pyclass] can only be used with C-style structs");
        }

        impl_class(&class.ident, &attr, doc, descriptors)
    }

    /// Parses `#[pyo3(get, set)]`
    fn parse_descriptors(item: &mut syn::Field) -> syn::Result<Vec<FnType>> {
        let mut descs = Vec::new();
        let mut new_attrs = Vec::new();
        for attr in item.attrs.drain(..) {
            if let Ok(syn::Meta::List(list)) = attr.parse_meta() {
                if list.path.is_ident("pyo3") {
                    for meta in list.nested.iter() {
                        if let syn::NestedMeta::Meta(metaitem) = meta {
                            if metaitem.path().is_ident("get") {
                                descs.push(FnType::Getter(SelfType::Receiver { mutable: false }));
                            } else if metaitem.path().is_ident("set") {
                                descs.push(FnType::Setter(SelfType::Receiver { mutable: true }));
                            } else {
                                bail_spanned!(metaitem.span() => "only get and set are supported");
                            }
                        }
                    }
                } else {
                    new_attrs.push(attr)
                }
            } else {
                new_attrs.push(attr);
            }
        }
        item.attrs = new_attrs;
        Ok(descs)
    }

    /// To allow multiple #[pymethods]/#[pyproto] block, we define inventory types.
    fn impl_methods_inventory(cls: &syn::Ident) -> TokenStream {
        // Try to build a unique type for better error messages
        let name = format!("Pyo3MethodsInventoryFor{}", cls.unraw());
        let inventory_cls = syn::Ident::new(&name, Span::call_site());

        quote! {
            #[doc(hidden)]
            pub struct #inventory_cls {
                methods: Vec<pyo3::class::PyMethodDefType>,
            }
            impl pyo3::class::methods::PyMethodsInventory for #inventory_cls {
                fn new(methods: Vec<pyo3::class::PyMethodDefType>) -> Self {
                    Self { methods }
                }
                fn get(&'static self) -> &'static [pyo3::class::PyMethodDefType] {
                    &self.methods
                }
            }

            impl pyo3::class::methods::HasMethodsInventory for #cls {
                type Methods = #inventory_cls;
            }

            pyo3::inventory::collect!(#inventory_cls);
        }
    }

    fn get_class_python_name<'a>(cls: &'a syn::Ident, attr: &'a PyClassArgs) -> &'a syn::Ident {
        attr.name.as_ref().unwrap_or(cls)
    }

    fn impl_class(
        cls: &syn::Ident,
        attr: &PyClassArgs,
        doc: syn::LitStr,
        descriptors: Vec<(syn::Field, Vec<FnType>)>,
    ) -> syn::Result<TokenStream> {
        let cls_name = get_class_python_name(cls, attr).to_string();

        let extra = {
            if let Some(freelist) = &attr.freelist {
                quote! {
                    impl pyo3::freelist::PyClassWithFreeList for #cls {
                        #[inline]
                        fn get_free_list(_py: pyo3::Python) -> &mut pyo3::freelist::FreeList<*mut pyo3::ffi::PyObject> {
                            static mut FREELIST: *mut pyo3::freelist::FreeList<*mut pyo3::ffi::PyObject> = 0 as *mut _;
                            unsafe {
                                if FREELIST.is_null() {
                                    FREELIST = Box::into_raw(Box::new(
                                        pyo3::freelist::FreeList::with_capacity(#freelist)));
                                }
                                &mut *FREELIST
                            }
                        }
                    }
                }
            } else {
                quote! {
                    impl pyo3::pyclass::PyClassAlloc for #cls {}
                }
            }
        };

        let extra = if !descriptors.is_empty() {
            let path = syn::Path::from(syn::PathSegment::from(cls.clone()));
            let ty = syn::Type::from(syn::TypePath { path, qself: None });
            let desc_impls = impl_descriptors(&ty, descriptors)?;
            quote! {
                #desc_impls
                #extra
            }
        } else {
            extra
        };

        // insert space for weak ref
        let mut has_weakref = false;
        let mut has_dict = false;
        let mut has_gc = false;
        for f in attr.flags.iter() {
            if let syn::Expr::Path(epath) = f {
                if epath.path == parse_quote! { pyo3::type_flags::WEAKREF } {
                    has_weakref = true;
                } else if epath.path == parse_quote! { pyo3::type_flags::DICT } {
                    has_dict = true;
                } else if epath.path == parse_quote! { pyo3::type_flags::GC } {
                    has_gc = true;
                }
            }
        }

        let weakref = if has_weakref {
            quote! { pyo3::pyclass_slots::PyClassWeakRefSlot }
        } else if attr.has_extends {
            quote! { <Self::BaseType as pyo3::derive_utils::PyBaseTypeUtils>::WeakRef }
        } else {
            quote! { pyo3::pyclass_slots::PyClassDummySlot }
        };
        let dict = if has_dict {
            quote! { pyo3::pyclass_slots::PyClassDictSlot }
        } else if attr.has_extends {
            quote! { <Self::BaseType as pyo3::derive_utils::PyBaseTypeUtils>::Dict }
        } else {
            quote! { pyo3::pyclass_slots::PyClassDummySlot }
        };
        let module = if let Some(m) = &attr.module {
            quote! { Some(#m) }
        } else {
            quote! { None }
        };

        // Enforce at compile time that PyGCProtocol is implemented
        let gc_impl = if has_gc {
            let closure_name = format!("__assertion_closure_{}", cls);
            let closure_token = syn::Ident::new(&closure_name, Span::call_site());
            quote! {
                fn #closure_token() {
                    use pyo3::class;

                    fn _assert_implements_protocol<'p, T: pyo3::class::PyGCProtocol<'p>>() {}
                    _assert_implements_protocol::<#cls>();
                }
            }
        } else {
            quote! {}
        };

        let impl_inventory = impl_methods_inventory(&cls);

        let base = &attr.base;
        let flags = &attr.flags;
        let extended = if attr.has_extends {
            quote! { pyo3::type_flags::EXTENDED }
        } else {
            quote! { 0 }
        };
        let base_layout = if attr.has_extends {
            quote! { <Self::BaseType as pyo3::derive_utils::PyBaseTypeUtils>::LayoutAsBase }
        } else {
            quote! { pyo3::pycell::PyCellBase<pyo3::PyAny> }
        };
        let base_nativetype = if attr.has_extends {
            quote! { <Self::BaseType as pyo3::derive_utils::PyBaseTypeUtils>::BaseNativeType }
        } else {
            quote! { pyo3::PyAny }
        };

        // If #cls is not extended type, we allow Self->PyObject conversion
        let into_pyobject = if !attr.has_extends {
            quote! {
                impl pyo3::IntoPy<pyo3::PyObject> for #cls {
                    fn into_py(self, py: pyo3::Python) -> pyo3::PyObject {
                        pyo3::IntoPy::into_py(pyo3::Py::new(py, self).unwrap(), py)
                    }
                }
            }
        } else {
            quote! {}
        };

        let thread_checker = if attr.has_unsendable {
            quote! { pyo3::pyclass::ThreadCheckerImpl<#cls> }
        } else if attr.has_extends {
            quote! {
                pyo3::pyclass::ThreadCheckerInherited<#cls, <#cls as pyo3::type_object::PyTypeInfo>::BaseType>
            }
        } else {
            quote! { pyo3::pyclass::ThreadCheckerStub<#cls> }
        };

        Ok(quote! {
            unsafe impl pyo3::type_object::PyTypeInfo for #cls {
                type Type = #cls;
                type BaseType = #base;
                type Layout = pyo3::PyCell<Self>;
                type BaseLayout = #base_layout;
                type Initializer = pyo3::pyclass_init::PyClassInitializer<Self>;
                type AsRefTarget = pyo3::PyCell<Self>;

                const NAME: &'static str = #cls_name;
                const MODULE: Option<&'static str> = #module;
                const DESCRIPTION: &'static str = #doc;
                const FLAGS: usize = #(#flags)|* | #extended;

                #[inline]
                fn type_object_raw(py: pyo3::Python) -> *mut pyo3::ffi::PyTypeObject {
                    use pyo3::type_object::LazyStaticType;
                    static TYPE_OBJECT: LazyStaticType = LazyStaticType::new();
                    TYPE_OBJECT.get_or_init::<Self>(py)
                }
            }

            impl pyo3::PyClass for #cls {
                type Dict = #dict;
                type WeakRef = #weakref;
                type BaseNativeType = #base_nativetype;
            }

            impl<'a> pyo3::derive_utils::ExtractExt<'a> for &'a #cls
            {
                type Target = pyo3::PyRef<'a, #cls>;
            }

            impl<'a> pyo3::derive_utils::ExtractExt<'a> for &'a mut #cls
            {
                type Target = pyo3::PyRefMut<'a, #cls>;
            }

            impl pyo3::pyclass::PyClassSend for #cls {
                type ThreadChecker = #thread_checker;
            }

            #into_pyobject

            #impl_inventory

            impl pyo3::class::proto_methods::PyProtoMethods for #cls {
                fn for_each_proto_slot<Visitor: FnMut(pyo3::ffi::PyType_Slot)>(visitor: Visitor) {
                    // Implementation which uses dtolnay specialization to load all slots.
                    use pyo3::class::proto_methods::*;
                    let protocols = PyClassProtocols::<#cls>::new();
                    protocols.object_protocol_slots()
                        .iter()
                        .chain(protocols.number_protocol_slots())
                        .chain(protocols.iter_protocol_slots())
                        .chain(protocols.gc_protocol_slots())
                        .chain(protocols.descr_protocol_slots())
                        .chain(protocols.mapping_protocol_slots())
                        .chain(protocols.sequence_protocol_slots())
                        .chain(protocols.async_protocol_slots())
                        .chain(protocols.buffer_protocol_slots())
                        .cloned()
                        .for_each(visitor);
                }

                fn get_buffer() -> Option<&'static pyo3::class::proto_methods::PyBufferProcs> {
                    use pyo3::class::proto_methods::*;
                    let protocols = PyClassProtocols::<#cls>::new();
                    protocols.buffer_procs()
                }
            }

            #extra

            #gc_impl
        })
    }

    fn impl_descriptors(
        cls: &syn::Type,
        descriptors: Vec<(syn::Field, Vec<FnType>)>,
    ) -> syn::Result<TokenStream> {
        let py_methods: Vec<TokenStream> = descriptors
            .iter()
            .flat_map(|(field, fns)| {
                fns.iter()
                    .map(|desc| {
                        let name = field.ident.as_ref().unwrap().unraw();
                        let doc = utils::get_doc(&field.attrs, None, true)
                            .unwrap_or_else(|_| syn::LitStr::new(&name.to_string(), name.span()));

                        match desc {
                            FnType::Getter(self_ty) => Ok(impl_py_getter_def(
                                &name,
                                &doc,
                                &impl_wrap_getter(&cls, PropertyType::Descriptor(&field), &self_ty)?,
                            )),
                            FnType::Setter(self_ty) => Ok(impl_py_setter_def(
                                &name,
                                &doc,
                                &impl_wrap_setter(&cls, PropertyType::Descriptor(&field), &self_ty)?,
                            )),
                            _ => unreachable!(),
                        }
                    })
                    .collect::<Vec<syn::Result<TokenStream>>>()
            })
            .collect::<syn::Result<_>>()?;

        Ok(quote! {
            pyo3::inventory::submit! {
                #![crate = pyo3] {
                    type Inventory = <#cls as pyo3::class::methods::HasMethodsInventory>::Methods;
                    <Inventory as pyo3::class::methods::PyMethodsInventory>::new(vec![#(#py_methods),*])
                }
            }
        })
    }