8e1f660e1d
# Objective Emitting compile errors produces cleaner messages than panicking in a proc-macro. ## Solution - Replace match-with-panic code with call to new `bevy_macro_utils::get_named_struct_fields` function - Replace one use of match-with-panic for enums with inline match _Aside:_ I'm also the maintainer of [`darling`](https://docs.rs/darling), a crate which provides a serde-like API for parsing macro inputs. I avoided using it here because it seemed like overkill, but if there are plans to add lots more attributes/macros then that might be a good way of offloading macro error handling.
44 lines
1.5 KiB
Rust
44 lines
1.5 KiB
Rust
use bevy_macro_utils::BevyManifest;
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use proc_macro::{Span, TokenStream};
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use quote::quote;
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use syn::{parse_macro_input, Data, DeriveInput};
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pub fn derive_enum_variant_meta(input: TokenStream) -> TokenStream {
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let ast = parse_macro_input!(input as DeriveInput);
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let variants = match &ast.data {
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Data::Enum(v) => &v.variants,
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_ => {
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return syn::Error::new(Span::call_site().into(), "Only enums are supported")
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.into_compile_error()
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.into()
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}
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};
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let bevy_util_path = BevyManifest::default().get_path(crate::modules::BEVY_UTILS);
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let generics = ast.generics;
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let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
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let struct_name = &ast.ident;
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let idents = variants.iter().map(|v| &v.ident);
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let names = variants.iter().map(|v| v.ident.to_string());
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let indices = 0..names.len();
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TokenStream::from(quote! {
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impl #impl_generics #bevy_util_path::EnumVariantMeta for #struct_name #ty_generics #where_clause {
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fn enum_variant_index(&self) -> usize {
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match self {
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#(#struct_name::#idents {..} => #indices,)*
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}
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}
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fn enum_variant_name(&self) -> &'static str {
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static variants: &[&str] = &[
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#(#names,)*
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];
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let index = self.enum_variant_index();
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variants[index]
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}
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}
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})
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}
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