darling_core/options/
from_variant.rs

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1use proc_macro2::TokenStream;
2use quote::ToTokens;
3use syn::{DeriveInput, Field, Ident, Meta};
4
5use crate::codegen::FromVariantImpl;
6use crate::options::{DataShape, OuterFrom, ParseAttribute, ParseData};
7use crate::{FromMeta, Result};
8
9#[derive(Debug, Clone)]
10pub struct FromVariantOptions {
11    pub base: OuterFrom,
12    /// The field on the deriving struct into which the discriminant expression
13    /// should be placed by the derived `FromVariant` impl.
14    pub discriminant: Option<Ident>,
15    pub fields: Option<Ident>,
16    pub supports: Option<DataShape>,
17}
18
19impl FromVariantOptions {
20    pub fn new(di: &DeriveInput) -> Result<Self> {
21        (FromVariantOptions {
22            base: OuterFrom::start(di)?,
23            discriminant: Default::default(),
24            fields: Default::default(),
25            supports: Default::default(),
26        })
27        .parse_attributes(&di.attrs)?
28        .parse_body(&di.data)
29    }
30}
31
32impl<'a> From<&'a FromVariantOptions> for FromVariantImpl<'a> {
33    fn from(v: &'a FromVariantOptions) -> Self {
34        FromVariantImpl {
35            base: (&v.base.container).into(),
36            ident: v.base.ident.as_ref(),
37            discriminant: v.discriminant.as_ref(),
38            fields: v.fields.as_ref(),
39            attr_names: &v.base.attr_names,
40            forward_attrs: v.base.as_forward_attrs(),
41            from_ident: v.base.from_ident,
42            supports: v.supports.as_ref(),
43        }
44    }
45}
46
47impl ParseAttribute for FromVariantOptions {
48    fn parse_nested(&mut self, mi: &Meta) -> Result<()> {
49        if mi.path().is_ident("supports") {
50            self.supports = FromMeta::from_meta(mi)?;
51            Ok(())
52        } else {
53            self.base.parse_nested(mi)
54        }
55    }
56}
57
58impl ParseData for FromVariantOptions {
59    fn parse_field(&mut self, field: &Field) -> Result<()> {
60        match field.ident.as_ref().map(|v| v.to_string()).as_deref() {
61            Some("discriminant") => {
62                self.discriminant.clone_from(&field.ident);
63                Ok(())
64            }
65            Some("fields") => {
66                self.fields.clone_from(&field.ident);
67                Ok(())
68            }
69            _ => self.base.parse_field(field),
70        }
71    }
72
73    fn validate_body(&self, errors: &mut crate::error::Accumulator) {
74        self.base.validate_body(errors);
75    }
76}
77
78impl ToTokens for FromVariantOptions {
79    fn to_tokens(&self, tokens: &mut TokenStream) {
80        FromVariantImpl::from(self).to_tokens(tokens)
81    }
82}
darling_core/options/from_variant.rs

darling_core/options/
from_variant.rs
