darling_core/codegen/
variant_data.rs

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1use proc_macro2::TokenStream;
2use quote::quote;
3
4use crate::ast::{Fields, Style};
5use crate::codegen::Field;
6
7pub struct FieldsGen<'a> {
8    fields: &'a Fields<Field<'a>>,
9    allow_unknown_fields: bool,
10}
11
12impl<'a> FieldsGen<'a> {
13    pub fn new(fields: &'a Fields<Field<'a>>, allow_unknown_fields: bool) -> Self {
14        Self {
15            fields,
16            allow_unknown_fields,
17        }
18    }
19
20    /// Create declarations for all the fields in the struct.
21    pub(in crate::codegen) fn declarations(&self) -> TokenStream {
22        match *self.fields {
23            Fields {
24                style: Style::Struct,
25                ref fields,
26                ..
27            } => {
28                let vdr = fields.iter().map(Field::as_declaration);
29                quote!(#(#vdr)*)
30            }
31            _ => panic!("FieldsGen doesn't support tuples yet"),
32        }
33    }
34
35    /// Generate the loop which walks meta items looking for property matches.
36    pub(in crate::codegen) fn core_loop(&self) -> TokenStream {
37        let arms = self.fields.as_ref().map(Field::as_match);
38        // If there is a flatten field, buffer the unknown field so it can be passed
39        // to the flatten function with all other unknown fields.
40        let handle_unknown = if self.fields.iter().any(|f| f.flatten) {
41            quote! {
42                __flatten.push(::darling::ast::NestedMeta::Meta(__inner.clone()));
43            }
44        }
45        // If we're allowing unknown fields, then handling one is a no-op.
46        else if self.allow_unknown_fields {
47            quote!()
48        }
49        // Otherwise, we're going to push a new spanned error pointing at the field.
50        else {
51            let mut names = self.fields.iter().filter_map(Field::as_name).peekable();
52            // We can't call `unknown_field_with_alts` with an empty slice, or else it fails to
53            // infer the type of the slice item.
54            let err_fn = if names.peek().is_none() {
55                quote!(unknown_field(__other))
56            } else {
57                quote!(unknown_field_with_alts(__other, &[#(#names),*]))
58            };
59
60            quote! {
61                __errors.push(::darling::Error::#err_fn.with_span(__inner));
62            }
63        };
64        let arms = arms.iter();
65
66        quote!(
67            for __item in __items {
68                match *__item {
69                    ::darling::export::NestedMeta::Meta(ref __inner) => {
70                        let __name = ::darling::util::path_to_string(__inner.path());
71                        match __name.as_str() {
72                            #(#arms)*
73                            __other => { #handle_unknown }
74                        }
75                    }
76                    ::darling::export::NestedMeta::Lit(ref __inner) => {
77                        __errors.push(::darling::Error::unsupported_format("literal")
78                            .with_span(__inner));
79                    }
80                }
81            }
82        )
83    }
84
85    pub fn require_fields(&self) -> TokenStream {
86        match *self.fields {
87            Fields {
88                style: Style::Struct,
89                ref fields,
90                ..
91            } => {
92                let checks = fields.iter().map(Field::as_presence_check);
93                quote!(#(#checks)*)
94            }
95            _ => panic!("FieldsGen doesn't support tuples for requirement checks"),
96        }
97    }
98
99    pub(in crate::codegen) fn initializers(&self) -> TokenStream {
100        let inits = self.fields.as_ref().map(Field::as_initializer);
101        let inits = inits.iter();
102
103        quote!(#(#inits),*)
104    }
105}
darling_core/codegen/variant_data.rs

darling_core/codegen/
variant_data.rs
