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}
106