[Merged by Bors] - EnumVariantMeta derive

crates/bevy_derive/src/enum_variant_meta.rs

@@ -0,0 +1,40 @@
+use crate::modules::{get_modules, get_path};
+use proc_macro::TokenStream;
+use quote::quote;
+use syn::{parse_macro_input, Data, DeriveInput};
+
+pub fn derive_enum_variant_meta(input: TokenStream) -> TokenStream {
+    let ast = parse_macro_input!(input as DeriveInput);
+    let variants = match &ast.data {
+        Data::Enum(v) => &v.variants,
+        _ => panic!("Expected an enum."),
+    };
+
+    let modules = get_modules(&ast.attrs);
+    let bevy_util_path = get_path(&modules.bevy_utils);
+
+    let generics = ast.generics;
+    let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
+
+    let struct_name = &ast.ident;
+    let idents = variants.iter().map(|v| &v.ident);
+    let names = variants.iter().map(|v| v.ident.to_string());
+    let indices = 0..names.len();
+
+    TokenStream::from(quote! {
+        impl #impl_generics #bevy_util_path::EnumVariantMeta for #struct_name#ty_generics #where_clause {
+            fn enum_variant_index(&self) -> usize {
+                match self {
+                    #(#struct_name::#idents {..} => #indices,)*
+                }
+            }
+            fn enum_variant_name(&self) -> &'static str {
+                static variants: &[&str] = &[
+                    #(#names,)*
+                ];
+                let index = self.enum_variant_index();
+                variants[index]
+            }
+        }
+    })
+}

crates/bevy_derive/src/lib.rs

@@ -3,6 +3,7 @@ extern crate proc_macro;
 mod app_plugin;
 mod bevy_main;
 mod bytes;
+mod enum_variant_meta;
 mod modules;
 mod render_resource;
 mod render_resources;
@@ -54,3 +55,8 @@ pub fn derive_dynamic_plugin(input: TokenStream) -> TokenStream {
 pub fn bevy_main(attr: TokenStream, item: TokenStream) -> TokenStream {
     bevy_main::bevy_main(attr, item)
 }
+
+#[proc_macro_derive(EnumVariantMeta, attributes(as_crate))]
+pub fn derive_enum_variant_meta(input: TokenStream) -> TokenStream {
+    enum_variant_meta::derive_enum_variant_meta(input)
+}

crates/bevy_derive/src/modules.rs

@@ -7,6 +7,7 @@ pub struct Modules {
     pub bevy_render: String,
     pub bevy_asset: String,
     pub bevy_core: String,
+    pub bevy_utils: String,
     pub bevy_app: String,
 }
 
@@ -16,6 +17,7 @@ impl Modules {
             bevy_asset: format!("{}::asset", name),
             bevy_render: format!("{}::render", name),
             bevy_core: format!("{}::core", name),
+            bevy_utils: format!("{}::utils", name),
             bevy_app: format!("{}::app", name),
         }
     }
@@ -25,6 +27,7 @@ impl Modules {
             bevy_asset: "bevy_asset".to_string(),
             bevy_render: "bevy_render".to_string(),
             bevy_core: "bevy_core".to_string(),
+            bevy_utils: "bevy_utils".to_string(),
             bevy_app: "bevy_app".to_string(),
         }
     }

crates/bevy_render/src/mesh/mesh.rs

@@ -15,6 +15,7 @@ use bevy_ecs::{
 };
 use bevy_math::*;
 use bevy_reflect::TypeUuid;
+use bevy_utils::EnumVariantMeta;
 use std::{borrow::Cow, collections::BTreeMap};
 
 use crate::pipeline::{InputStepMode, VertexAttribute, VertexBufferLayout};
@@ -24,7 +25,7 @@ pub const INDEX_BUFFER_ASSET_INDEX: u64 = 0;
 pub const VERTEX_ATTRIBUTE_BUFFER_ID: u64 = 10;
 
 /// An array where each entry describes a property of a single vertex.
-#[derive(Clone, Debug)]
+#[derive(Clone, Debug, EnumVariantMeta)]
 pub enum VertexAttributeValues {
     Float(Vec<f32>),
     Int(Vec<i32>),