darling_core/codegen/
from_field.rs

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1use proc_macro2::TokenStream;
2use quote::{quote, ToTokens};
3use syn::Ident;
4
5use crate::{
6    codegen::{ExtractAttribute, OuterFromImpl, TraitImpl},
7    util::PathList,
8};
9
10use super::ForwardAttrs;
11
12/// `impl FromField` generator. This is used for parsing an individual
13/// field and its attributes.
14pub struct FromFieldImpl<'a> {
15    pub ident: Option<&'a Ident>,
16    pub vis: Option<&'a Ident>,
17    pub ty: Option<&'a Ident>,
18    pub base: TraitImpl<'a>,
19    pub attr_names: &'a PathList,
20    pub forward_attrs: ForwardAttrs<'a>,
21    pub from_ident: bool,
22}
23
24impl<'a> ToTokens for FromFieldImpl<'a> {
25    fn to_tokens(&self, tokens: &mut TokenStream) {
26        let input = self.param_name();
27
28        let error_declaration = self.base.declare_errors();
29        let require_fields = self.base.require_fields();
30        let error_check = self.base.check_errors();
31
32        let initializers = self.base.initializers();
33
34        let default = if self.from_ident {
35            quote!(let __default: Self = ::darling::export::From::from(#input.ident.clone());)
36        } else {
37            self.base.fallback_decl()
38        };
39
40        let passed_ident = self
41            .ident
42            .as_ref()
43            .map(|i| quote!(#i: #input.ident.clone(),));
44        let passed_vis = self.vis.as_ref().map(|i| quote!(#i: #input.vis.clone(),));
45        let passed_ty = self.ty.as_ref().map(|i| quote!(#i: #input.ty.clone(),));
46        let passed_attrs = self.forward_attrs.as_initializer();
47
48        // Determine which attributes to forward (if any).
49        let grab_attrs = self.extractor();
50        let post_transform = self.base.post_transform_call();
51
52        self.wrap(
53            quote! {
54                fn from_field(#input: &::darling::export::syn::Field) -> ::darling::Result<Self> {
55                    #error_declaration
56
57                    #grab_attrs
58
59                    #require_fields
60
61                    #error_check
62
63                    #default
64
65                    ::darling::export::Ok(Self {
66                        #passed_ident
67                        #passed_ty
68                        #passed_vis
69                        #passed_attrs
70                        #initializers
71                    }) #post_transform
72
73                }
74            },
75            tokens,
76        );
77    }
78}
79
80impl<'a> ExtractAttribute for FromFieldImpl<'a> {
81    fn attr_names(&self) -> &PathList {
82        self.attr_names
83    }
84
85    fn forward_attrs(&self) -> &super::ForwardAttrs<'_> {
86        &self.forward_attrs
87    }
88
89    fn param_name(&self) -> TokenStream {
90        quote!(__field)
91    }
92
93    fn core_loop(&self) -> TokenStream {
94        self.base.core_loop()
95    }
96
97    fn local_declarations(&self) -> TokenStream {
98        self.base.local_declarations()
99    }
100}
101
102impl<'a> OuterFromImpl<'a> for FromFieldImpl<'a> {
103    fn trait_path(&self) -> syn::Path {
104        path!(::darling::FromField)
105    }
106
107    fn trait_bound(&self) -> syn::Path {
108        path!(::darling::FromMeta)
109    }
110
111    fn base(&'a self) -> &'a TraitImpl<'a> {
112        &self.base
113    }
114}
darling_core/codegen/from_field.rs

darling_core/codegen/
from_field.rs
