|
| 1 | +use proc_macro2::TokenStream; |
| 2 | +use quote::quote; |
| 3 | +use syn::{Attribute, DeriveInput, Field, Meta, MetaList, NestedMeta, Result}; |
| 4 | + |
| 5 | +struct TraverseAttr { |
| 6 | + /// set to `true` if the attribute is `#[pytraverse(skip)]` |
| 7 | + skip: bool, |
| 8 | +} |
| 9 | + |
| 10 | +const ATTR_TRAVERSE: &str = "pytraverse"; |
| 11 | + |
| 12 | +/// get the `#[pytraverse(..)]` attribute from the struct |
| 13 | +fn valid_get_traverse_attr_from_meta_list(list: &MetaList) -> Result<TraverseAttr> { |
| 14 | + let find_skip_and_only_skip = || { |
| 15 | + let len = list.nested.len(); |
| 16 | + if len != 1 { |
| 17 | + return None; |
| 18 | + } |
| 19 | + let mut iter = list.nested.iter(); |
| 20 | + // we have checked the length, so unwrap is safe |
| 21 | + let first_arg = iter.next().unwrap(); |
| 22 | + let skip = match first_arg { |
| 23 | + NestedMeta::Meta(Meta::Path(path)) => match path.is_ident("skip") { |
| 24 | + true => true, |
| 25 | + false => return None, |
| 26 | + }, |
| 27 | + _ => return None, |
| 28 | + }; |
| 29 | + Some(skip) |
| 30 | + }; |
| 31 | + let skip = find_skip_and_only_skip().ok_or_else(|| { |
| 32 | + err_span!( |
| 33 | + list, |
| 34 | + "only support attr is #[pytraverse(skip)], got arguments: {:?}", |
| 35 | + list.nested |
| 36 | + ) |
| 37 | + })?; |
| 38 | + Ok(TraverseAttr { skip }) |
| 39 | +} |
| 40 | + |
| 41 | +/// only accept `#[pytraverse(skip)]` for now |
| 42 | +fn pytraverse_arg(attr: &Attribute) -> Option<Result<TraverseAttr>> { |
| 43 | + if !attr.path.is_ident(ATTR_TRAVERSE) { |
| 44 | + return None; |
| 45 | + } |
| 46 | + let ret = || { |
| 47 | + let parsed = attr.parse_meta()?; |
| 48 | + if let Meta::List(list) = parsed { |
| 49 | + valid_get_traverse_attr_from_meta_list(&list) |
| 50 | + } else { |
| 51 | + bail_span!(attr, "pytraverse must be a list, like #[pytraverse(skip)]") |
| 52 | + } |
| 53 | + }; |
| 54 | + Some(ret()) |
| 55 | +} |
| 56 | + |
| 57 | +fn field_to_traverse_code(field: &Field) -> Result<TokenStream> { |
| 58 | + let pytraverse_attrs = field |
| 59 | + .attrs |
| 60 | + .iter() |
| 61 | + .filter_map(pytraverse_arg) |
| 62 | + .collect::<std::result::Result<Vec<_>, _>>()?; |
| 63 | + let do_trace = if pytraverse_attrs.len() > 1 { |
| 64 | + bail_span!( |
| 65 | + field, |
| 66 | + "found multiple #[pytraverse] attributes on the same field, expect at most one" |
| 67 | + ) |
| 68 | + } else if pytraverse_attrs.is_empty() { |
| 69 | + // default to always traverse every field |
| 70 | + true |
| 71 | + } else { |
| 72 | + !pytraverse_attrs[0].skip |
| 73 | + }; |
| 74 | + let name = field.ident.as_ref().ok_or_else(|| { |
| 75 | + syn::Error::new_spanned( |
| 76 | + field.clone(), |
| 77 | + "Field should have a name in non-tuple struct", |
| 78 | + ) |
| 79 | + })?; |
| 80 | + if do_trace { |
| 81 | + Ok(quote!( |
| 82 | + ::rustpython_vm::object::Traverse::traverse(&self.#name, tracer_fn); |
| 83 | + )) |
| 84 | + } else { |
| 85 | + Ok(quote!()) |
| 86 | + } |
| 87 | +} |
| 88 | + |
| 89 | +/// not trace corresponding field |
| 90 | +fn gen_trace_code(item: &mut DeriveInput) -> Result<TokenStream> { |
| 91 | + match &mut item.data { |
| 92 | + syn::Data::Struct(s) => { |
| 93 | + let fields = &mut s.fields; |
| 94 | + match fields { |
| 95 | + syn::Fields::Named(ref mut fields) => { |
| 96 | + let res: Vec<TokenStream> = fields |
| 97 | + .named |
| 98 | + .iter_mut() |
| 99 | + .map(|f| -> Result<TokenStream> { field_to_traverse_code(f) }) |
| 100 | + .collect::<Result<_>>()?; |
| 101 | + let res = res.into_iter().collect::<TokenStream>(); |
| 102 | + Ok(res) |
| 103 | + } |
| 104 | + syn::Fields::Unnamed(fields) => { |
| 105 | + let res: TokenStream = (0..fields.unnamed.len()) |
| 106 | + .map(|i| { |
| 107 | + let i = syn::Index::from(i); |
| 108 | + quote!( |
| 109 | + ::rustpython_vm::object::Traverse::traverse(&self.#i, tracer_fn); |
| 110 | + ) |
| 111 | + }) |
| 112 | + .collect(); |
| 113 | + Ok(res) |
| 114 | + } |
| 115 | + _ => Err(syn::Error::new_spanned( |
| 116 | + fields, |
| 117 | + "Only named and unnamed fields are supported", |
| 118 | + )), |
| 119 | + } |
| 120 | + } |
| 121 | + _ => Err(syn::Error::new_spanned(item, "Only structs are supported")), |
| 122 | + } |
| 123 | +} |
| 124 | + |
| 125 | +pub(crate) fn impl_pytraverse(mut item: DeriveInput) -> Result<TokenStream> { |
| 126 | + let trace_code = gen_trace_code(&mut item)?; |
| 127 | + |
| 128 | + let ty = &item.ident; |
| 129 | + |
| 130 | + let ret = quote! { |
| 131 | + unsafe impl ::rustpython_vm::object::Traverse for #ty { |
| 132 | + fn traverse(&self, tracer_fn: &mut ::rustpython_vm::object::TraverseFn) { |
| 133 | + #trace_code |
| 134 | + } |
| 135 | + } |
| 136 | + }; |
| 137 | + Ok(ret) |
| 138 | +} |
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