darling_core/options/
outer_from.rs

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

darling_core/options/
outer_from.rs
