strum_macros/macros/strings/
from_string.rs
1use proc_macro2::TokenStream;
2use quote::quote;
3use syn::{Data, DeriveInput, Fields};
4
5use crate::helpers::{
6 non_enum_error, occurrence_error, HasInnerVariantProperties, HasStrumVariantProperties,
7 HasTypeProperties,
8};
9
10pub fn from_string_inner(ast: &DeriveInput) -> syn::Result<TokenStream> {
11 let name = &ast.ident;
12 let (impl_generics, ty_generics, where_clause) = ast.generics.split_for_impl();
13 let variants = match &ast.data {
14 Data::Enum(v) => &v.variants,
15 _ => return Err(non_enum_error()),
16 };
17
18 let type_properties = ast.get_type_properties()?;
19 let strum_module_path = type_properties.crate_module_path();
20
21 let mut default_kw = None;
22 let mut default =
23 quote! { ::core::result::Result::Err(#strum_module_path::ParseError::VariantNotFound) };
24
25 let mut phf_exact_match_arms = Vec::new();
26 let mut standard_match_arms = Vec::new();
27 for variant in variants {
28 let ident = &variant.ident;
29 let variant_properties = variant.get_variant_properties()?;
30
31 if variant_properties.disabled.is_some() {
32 continue;
33 }
34
35 if let Some(kw) = variant_properties.default {
36 if let Some(fst_kw) = default_kw {
37 return Err(occurrence_error(fst_kw, kw, "default"));
38 }
39
40 match &variant.fields {
41 Fields::Unnamed(fields) if fields.unnamed.len() == 1 => {}
42 _ => {
43 return Err(syn::Error::new_spanned(
44 variant,
45 "Default only works on newtype structs with a single String field",
46 ))
47 }
48 }
49 default_kw = Some(kw);
50 default = quote! {
51 ::core::result::Result::Ok(#name::#ident(s.into()))
52 };
53 continue;
54 }
55
56 let params = match &variant.fields {
57 Fields::Unit => quote! {},
58 Fields::Unnamed(fields) => {
59 if let Some(ref value) = variant_properties.default_with {
60 let func = proc_macro2::Ident::new(&value.value(), value.span());
61 let defaults = vec![quote! { #func() }];
62 quote! { (#(#defaults),*) }
63 } else {
64 let defaults =
65 ::core::iter::repeat(quote!(Default::default())).take(fields.unnamed.len());
66 quote! { (#(#defaults),*) }
67 }
68 }
69 Fields::Named(fields) => {
70 let mut defaults = vec![];
71 for field in &fields.named {
72 let meta = field.get_variant_inner_properties()?;
73 let field = field.ident.as_ref().unwrap();
74
75 if let Some(default_with) = meta.default_with {
76 let func =
77 proc_macro2::Ident::new(&default_with.value(), default_with.span());
78 defaults.push(quote! {
79 #field: #func()
80 });
81 } else {
82 defaults.push(quote! { #field: Default::default() });
83 }
84 }
85
86 quote! { {#(#defaults),*} }
87 }
88 };
89
90 let is_ascii_case_insensitive = variant_properties
91 .ascii_case_insensitive
92 .unwrap_or(type_properties.ascii_case_insensitive);
93
94 for serialization in variant_properties.get_serializations(type_properties.case_style) {
96 if type_properties.use_phf {
97 phf_exact_match_arms.push(quote! { #serialization => #name::#ident #params, });
98
99 if is_ascii_case_insensitive {
100 let ser_string = serialization.value();
102
103 let lower =
104 syn::LitStr::new(&ser_string.to_ascii_lowercase(), serialization.span());
105 let upper =
106 syn::LitStr::new(&ser_string.to_ascii_uppercase(), serialization.span());
107 phf_exact_match_arms.push(quote! { #lower => #name::#ident #params, });
108 phf_exact_match_arms.push(quote! { #upper => #name::#ident #params, });
109 standard_match_arms.push(quote! { s if s.eq_ignore_ascii_case(#serialization) => #name::#ident #params, });
110 }
111 } else {
112 standard_match_arms.push(if !is_ascii_case_insensitive {
113 quote! { #serialization => #name::#ident #params, }
114 } else {
115 quote! { s if s.eq_ignore_ascii_case(#serialization) => #name::#ident #params, }
116 });
117 }
118 }
119 }
120
121 let phf_body = if phf_exact_match_arms.is_empty() {
122 quote!()
123 } else {
124 quote! {
125 use #strum_module_path::_private_phf_reexport_for_macro_if_phf_feature as phf;
126 static PHF: phf::Map<&'static str, #name> = phf::phf_map! {
127 #(#phf_exact_match_arms)*
128 };
129 if let Some(value) = PHF.get(s).cloned() {
130 return ::core::result::Result::Ok(value);
131 }
132 }
133 };
134
135 let standard_match_body = if standard_match_arms.is_empty() {
136 default
137 } else {
138 quote! {
139 ::core::result::Result::Ok(match s {
140 #(#standard_match_arms)*
141 _ => return #default,
142 })
143 }
144 };
145
146 let from_str = quote! {
147 #[allow(clippy::use_self)]
148 impl #impl_generics ::core::str::FromStr for #name #ty_generics #where_clause {
149 type Err = #strum_module_path::ParseError;
150 fn from_str(s: &str) -> ::core::result::Result< #name #ty_generics , <Self as ::core::str::FromStr>::Err> {
151 #phf_body
152 #standard_match_body
153 }
154 }
155 };
156 let try_from_str = try_from_str(
157 name,
158 &impl_generics,
159 &ty_generics,
160 where_clause,
161 &strum_module_path,
162 );
163
164 Ok(quote! {
165 #from_str
166 #try_from_str
167 })
168}
169
170#[rustversion::before(1.34)]
171fn try_from_str(
172 _name: &proc_macro2::Ident,
173 _impl_generics: &syn::ImplGenerics,
174 _ty_generics: &syn::TypeGenerics,
175 _where_clause: Option<&syn::WhereClause>,
176 _strum_module_path: &syn::Path,
177) -> TokenStream {
178 Default::default()
179}
180
181#[rustversion::since(1.34)]
182fn try_from_str(
183 name: &proc_macro2::Ident,
184 impl_generics: &syn::ImplGenerics,
185 ty_generics: &syn::TypeGenerics,
186 where_clause: Option<&syn::WhereClause>,
187 strum_module_path: &syn::Path,
188) -> TokenStream {
189 quote! {
190 #[allow(clippy::use_self)]
191 impl #impl_generics ::core::convert::TryFrom<&str> for #name #ty_generics #where_clause {
192 type Error = #strum_module_path::ParseError;
193 fn try_from(s: &str) -> ::core::result::Result< #name #ty_generics , <Self as ::core::convert::TryFrom<&str>>::Error> {
194 ::core::str::FromStr::from_str(s)
195 }
196 }
197 }
198}