darling_core/options/
from_attributes.rs

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1use quote::ToTokens;
2
3use crate::{ast::Data, codegen::FromAttributesImpl, Error, Result};
4
5use super::{OuterFrom, ParseAttribute, ParseData};
6
7/// Receiver for derived `FromAttributes` impls.
8pub struct FromAttributesOptions {
9    // Note: FromAttributes has no behaviors beyond those common
10    // to all the `OuterFrom` traits.
11    pub base: OuterFrom,
12}
13
14impl FromAttributesOptions {
15    pub fn new(di: &syn::DeriveInput) -> Result<Self> {
16        let opts = (Self {
17            base: OuterFrom::start(di)?,
18        })
19        .parse_attributes(&di.attrs)?
20        .parse_body(&di.data)?;
21
22        if !opts.is_newtype() && opts.base.attr_names.is_empty() {
23            Err(Error::custom(
24                "FromAttributes without attributes collects nothing",
25            ))
26        } else {
27            Ok(opts)
28        }
29    }
30
31    fn is_newtype(&self) -> bool {
32        if let Data::Struct(ref data) = self.base.container.data {
33            data.is_newtype()
34        } else {
35            false
36        }
37    }
38}
39
40impl ParseAttribute for FromAttributesOptions {
41    fn parse_nested(&mut self, mi: &syn::Meta) -> Result<()> {
42        self.base.parse_nested(mi)
43    }
44}
45
46impl ParseData for FromAttributesOptions {
47    fn parse_variant(&mut self, variant: &syn::Variant) -> Result<()> {
48        self.base.parse_variant(variant)
49    }
50
51    fn parse_field(&mut self, field: &syn::Field) -> Result<()> {
52        self.base.parse_field(field)
53    }
54
55    fn validate_body(&self, errors: &mut crate::error::Accumulator) {
56        self.base.validate_body(errors);
57    }
58}
59
60impl<'a> From<&'a FromAttributesOptions> for FromAttributesImpl<'a> {
61    fn from(v: &'a FromAttributesOptions) -> Self {
62        FromAttributesImpl {
63            base: (&v.base.container).into(),
64            attr_names: &v.base.attr_names,
65            forward_attrs: v.base.as_forward_attrs(),
66        }
67    }
68}
69
70impl ToTokens for FromAttributesOptions {
71    fn to_tokens(&self, tokens: &mut proc_macro2::TokenStream) {
72        FromAttributesImpl::from(self).to_tokens(tokens)
73    }
74}
darling_core/options/from_attributes.rs

darling_core/options/
from_attributes.rs
