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use crate::{
convert_case::{Case, Casing},
proc_macro::TokenStream,
proc_macro2::TokenStream as TokenStream2,
quote::quote,
syn::{
parse::{Parse, ParseBuffer},
spanned::Spanned,
Data, DeriveInput, Error as SynError, Fields, Ident,
},
};
pub struct EnumMatch(pub TokenStream);
impl Parse for EnumMatch {
fn parse(input: &ParseBuffer) -> Result<Self, SynError> {
let input: DeriveInput = input.parse::<DeriveInput>()?;
if let Data::Enum(my_enum) = input.data {
let enum_name = input.ident;
let enum_name_string = enum_name.to_string();
let mut ts = TokenStream2::new();
'iter_fields: for variant in my_enum.variants {
for attribute in &variant.attrs {
if let Some(ident) = attribute.path.get_ident() {
if ident.to_string().eq("enum_match") {
if let Ok(tokens) = attribute.parse_args::<Ident>() {
if tokens.to_string().eq("ignore") {
break 'iter_fields;
} else {
return Err(SynError::new(
attribute.span(),
format!(
"Unexpected argument `{}` to attribute `enum_match`",
tokens
),
));
}
} else {
return Err(SynError::new(
attribute.span(),
"Cannot parse arguments to attribute `enum_match` as identifier",
));
}
}
}
}
let variant_name = variant.ident;
let variant_name_string = variant_name.to_string();
let variant_snake = variant_name_string.to_case(Case::Snake);
let am_function_string = format!("am_{}", variant_snake);
let am_function_ident = Ident::new(&am_function_string, variant_name.span());
match variant.fields {
Fields::Unnamed(_) => {
let doc = format!(
"Returns true if {} has value of {}.",
enum_name_string, variant_name_string
);
ts.extend(quote! {
#[doc = #doc ]
pub fn #am_function_ident(&self) -> bool {
matches!(self, #enum_name::#variant_name(_))
}
});
}
Fields::Named(_) => {
let doc = format!(
"Returns true if {} has value of {}.",
enum_name_string, variant_name_string
);
ts.extend(quote! {
#[doc = #doc ]
pub fn #am_function_ident(&self) -> bool {
matches!(self, #enum_name::#variant_name { .. })
}
});
}
Fields::Unit => {
let doc = format!(
"Returns true if {} has value of {}.",
enum_name_string, variant_name_string
);
ts.extend(quote! {
#[doc = #doc ]
pub fn #am_function_ident(&self) -> bool {
matches!(self, #enum_name::#variant_name)
}
});
}
}
}
let ts = quote! {
impl #enum_name {
#ts
}
}
.into();
return Ok(EnumMatch(ts));
} else {
return Err(SynError::new(
input.span(),
"Cannot derive `EnumMatch` on anything that is not an enum",
));
}
}
}