1use syn::spanned::Spanned;
2use syn::{Field, Ident, Meta};
3
4use crate::ast::Data;
5use crate::codegen::ForwardAttrs;
6use crate::options::{
7 Core, DefaultExpression, ForwardAttrsFilter, ForwardedField, ParseAttribute, ParseData,
8};
9use crate::util::PathList;
10use crate::{Error, FromField, FromMeta, Result};
11
12/// Reusable base for `FromDeriveInput`, `FromVariant`, `FromField`, and other top-level
13/// `From*` traits.
14#[derive(Debug, Clone)]
15pub struct OuterFrom {
16 /// The field on the target struct which should receive the type identifier, if any.
17 pub ident: Option<Ident>,
18
19 /// The field on the target struct which should receive the type attributes, if any.
20 pub attrs: Option<ForwardedField>,
21
22 pub container: Core,
23
24 /// The attribute names that should be searched.
25 pub attr_names: PathList,
26
27 /// The attribute names that should be forwarded. The presence of the word with no additional
28 /// filtering will cause _all_ attributes to be cloned and exposed to the struct after parsing.
29 pub forward_attrs: Option<ForwardAttrsFilter>,
30
31 /// Whether or not the container can be made through conversion from the type `Ident`.
32 pub from_ident: bool,
33}
34
35impl OuterFrom {
36 pub fn start(di: &syn::DeriveInput) -> Result<Self> {
37 Ok(OuterFrom {
38 container: Core::start(di)?,
39 attrs: Default::default(),
40 ident: Default::default(),
41 attr_names: Default::default(),
42 forward_attrs: Default::default(),
43 from_ident: Default::default(),
44 })
45 }
46
47 pub fn as_forward_attrs(&self) -> ForwardAttrs<'_> {
48 ForwardAttrs {
49 field: self.attrs.as_ref(),
50 filter: self.forward_attrs.as_ref(),
51 }
52 }
53}
54
55impl ParseAttribute for OuterFrom {
56 fn parse_nested(&mut self, mi: &Meta) -> Result<()> {
57 let path: &Path = mi.path();
58 if path.is_ident("attributes") {
59 self.attr_names = FromMeta::from_meta(item:mi)?;
60 } else if path.is_ident("forward_attrs") {
61 self.forward_attrs = FromMeta::from_meta(item:mi)?;
62 } else if path.is_ident("from_ident") {
63 // HACK: Declaring that a default is present will cause fields to
64 // generate correct code, but control flow isn't that obvious.
65 self.container.default = Some(DefaultExpression::Trait {
66 // Use the span of the `from_ident` keyword so that errors in generated code
67 // caused by this will point back to the correct location.
68 span: path.span(),
69 });
70 self.from_ident = true;
71 } else {
72 return self.container.parse_nested(mi);
73 }
74 Ok(())
75 }
76}
77
78impl ParseData for OuterFrom {
79 fn parse_field(&mut self, field: &Field) -> Result<()> {
80 match field.ident.as_ref().map(|v| v.to_string()).as_deref() {
81 Some("ident") => {
82 self.ident.clone_from(&field.ident);
83 Ok(())
84 }
85 Some("attrs") => {
86 self.attrs = ForwardedField::from_field(field).map(Some)?;
87 Ok(())
88 }
89 _ => self.container.parse_field(field),
90 }
91 }
92
93 fn validate_body(&self, errors: &mut crate::error::Accumulator) {
94 self.container.validate_body(errors);
95 if let Some(attrs) = &self.attrs {
96 if self.forward_attrs.is_none() {
97 let container_name = match &self.container.data {
98 Data::Enum(_) => "enum",
99 Data::Struct(_) => "struct",
100 };
101 errors.push(
102 Error::custom(format!(
103 "field will not be populated because `forward_attrs` is not set on the {}",
104 container_name
105 ))
106 .with_span(&attrs.ident),
107 );
108 }
109 }
110 }
111}
112