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Extract out attr parsing code into a separate function

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This commit is contained in:
greg 2018-05-02 19:30:34 -07:00
parent c0746028f4
commit 57ccdd5ead
1 changed files with 17 additions and 15 deletions
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32
schala-codegen/src/lib.rs
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@ -5,13 +5,28 @@ extern crate quote;
extern crate syn; extern crate syn;
use proc_macro::TokenStream; use proc_macro::TokenStream;
use syn::DeriveInput; use syn::{Attribute, DeriveInput};
#[proc_macro] #[proc_macro]
pub fn print_a_thing(_input: TokenStream) -> TokenStream { pub fn print_a_thing(_input: TokenStream) -> TokenStream {
"println!(\"Invoked from a proc macro\");".parse().unwrap() "println!(\"Invoked from a proc macro\");".parse().unwrap()
} }
fn extract_attribute_arg_by_name(name: &str, attrs: &Vec<Attribute>) -> Option<String> {
use syn::{Meta, Lit, MetaNameValue};
attrs.iter().map(|attr| attr.interpret_meta()).find(|meta| {
match meta {
&Some(Meta::NameValue(MetaNameValue { ident, .. })) if ident.as_ref() == name => true,
_ => false
}
}).and_then(|meta| {
match meta {
Some(Meta::NameValue(MetaNameValue { lit: Lit::Str(litstr), .. })) => Some(litstr.value()),
_ => None,
}
})
}
#[proc_macro_derive(ProgrammingLanguageInterface, attributes(LanguageName, FileExtension, PipelineSteps))] #[proc_macro_derive(ProgrammingLanguageInterface, attributes(LanguageName, FileExtension, PipelineSteps))]
pub fn derive_programming_language_interface(input: TokenStream) -> TokenStream { pub fn derive_programming_language_interface(input: TokenStream) -> TokenStream {
@ -19,20 +34,7 @@ pub fn derive_programming_language_interface(input: TokenStream) -> TokenStream
let name = &ast.ident; let name = &ast.ident;
let attrs = &ast.attrs; let attrs = &ast.attrs;
let language_name: String = extract_attribute_arg_by_name("LanguageName", attrs).unwrap();
let extracted_lang_name: Option<String> = attrs.iter().map(|attr| attr.interpret_meta()).find(|meta| {
match meta {
&Some(syn::Meta::NameValue(syn::MetaNameValue { ident, .. })) if ident.as_ref() == "LanguageName" => true,
_ => false
}
}).and_then(|meta| {
match meta {
Some(syn::Meta::NameValue(syn::MetaNameValue { lit: syn::Lit::Str(litstr), .. })) => Some(litstr.value()),
_ => None,
}
});
let language_name = extracted_lang_name.unwrap();
println!("LANG NAME: {:?}", language_name); println!("LANG NAME: {:?}", language_name);