derive World

Author: Nertsal

crates/stecs-derive/src/lib.rs

@@ -7,6 +7,16 @@ mod get;
 mod optic;
 mod query;
 mod split;
+mod world;
+
+#[proc_macro_derive(World, attributes(world))]
+pub fn derive_world(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    let input: syn::DeriveInput = syn::parse_macro_input!(input);
+    match world::WorldOpts::from_derive_input(&input) {
+        Ok(input) => input.derive().into(),
+        Err(e) => e.write_errors().into(),
+    }
+}
 
 #[proc_macro_derive(SplitFields, attributes(split))]
 pub fn derive_split_fields(input: proc_macro::TokenStream) -> proc_macro::TokenStream {

crates/stecs-derive/src/world.rs

@@ -0,0 +1,129 @@
+use crate::syn;
+
+use darling::{ast, FromDeriveInput, FromField};
+use proc_macro2::TokenStream;
+use quote::{quote, ToTokens};
+
+#[derive(FromDeriveInput)]
+#[darling(supports(struct_named), attributes(world))]
+pub struct WorldOpts {
+    ident: syn::Ident,
+    // vis: syn::Visibility,
+    data: ast::Data<(), FieldOpts>,
+    // generics: syn::Generics,
+}
+
+#[derive(FromField)]
+#[darling(attributes(split))]
+struct FieldOpts {
+    ident: Option<syn::Ident>,
+    // ty: syn::Type,
+    // groups: Option<Vec<()>>,
+}
+
+struct Struct {
+    name: syn::Ident,
+    // visibility: syn::Visibility,
+    fields: Vec<Field>,
+    // generics: syn::Generics,
+}
+
+struct Field {
+    name: syn::Ident,
+    // ty: syn::Type,
+    // groups: Vec<()>,
+}
+
+#[derive(thiserror::Error, Debug)]
+enum ParseError {
+    #[error("not a struct")]
+    NotAStruct,
+    #[error("field has no name")]
+    NamelessField,
+}
+
+impl TryFrom<WorldOpts> for Struct {
+    type Error = ParseError;
+
+    fn try_from(value: WorldOpts) -> Result<Self, Self::Error> {
+        let fields = value
+            .data
+            .take_struct()
+            .ok_or(ParseError::NotAStruct)?
+            .fields;
+        let fields = fields
+            .into_iter()
+            .map(|field| {
+                let name = field.ident.ok_or(ParseError::NamelessField)?;
+                Ok(Field {
+                    name,
+                    // ty: field.ty
+                })
+            })
+            .collect::<Result<Vec<Field>, ParseError>>()?;
+        Ok(Self {
+            name: value.ident,
+            // visibility: value.vis,
+            fields,
+            // generics: value.generics,
+        })
+    }
+}
+
+impl WorldOpts {
+    pub fn derive(self) -> TokenStream {
+        let query = Struct::try_from(self).unwrap_or_else(|err| panic!("{err}"));
+        query.derive()
+    }
+}
+
+impl Struct {
+    fn derive(self) -> TokenStream {
+        let world = self.name;
+
+        // impl Default for World
+        let default = {
+            let fields = self.fields.iter().map(|field| {
+                let name = &field.name;
+                quote! { #name: ::std::default::Default::default(), }
+            });
+
+            quote! {
+                impl ::std::default::Default for #world {
+                    fn default() -> Self {
+                        Self {
+                            #(#fields)*
+                        }
+                    }
+                }
+            }
+        };
+
+        let all_fields = self.fields.iter().map(|field| &field.name);
+        let query_all = generate_query(quote! { query_all }, all_fields);
+
+        quote! {
+            #default
+            #query_all
+        }
+    }
+}
+
+// macro_rules! query_all {
+//     ($world:expr, $args:tt) => {
+//         query!([$world.players, $world.enemies, $world.particles], $args)
+//     };
+// }
+fn generate_query(
+    name: impl ToTokens,
+    fields: impl IntoIterator<Item = impl ToTokens>,
+) -> TokenStream {
+    let fields = fields.into_iter().map(|field| quote! { $world.#field });
+    quote! {
+        macro_rules! #name {
+            ($world:expr, $args:tt) => {
+                query!([#(#fields),*], $args)
+            }
+        }
+    }
+}

examples/world.rs

@@ -1,12 +1,27 @@
 use stecs::prelude::*;
 
-// #[derive(World)]
+#[derive(World)]
 pub struct World {
+    #[world(groups = ["actor"])]
     pub players: StructOf<Dense<Player>>,
+    #[world(groups = ["actor"])]
     pub enemies: StructOf<Dense<Enemy>>,
+    #[world(groups = [])]
     pub particles: StructOf<Dense<Particle>>,
 }
 
+// macro_rules! query_all {
+//     ($world:expr, $args:tt) => {
+//         query!([$world.players, $world.enemies, $world.particles], $args)
+//     };
+// }
+
+// macro_rules! actors {
+//     ($world:expr) => {
+//         [$world.players, $world.enemies]
+//     };
+// }
+
 #[derive(SplitFields)]
 pub struct Position {
     pub x: f32,
@@ -43,4 +58,10 @@ pub struct Enemy {
     pub ai: EnemyAi,
 }
 
-fn main() {}
+fn main() {
+    let world = World::default();
+
+    for position in query_all!(world, (&position.x)) {
+        println!("entity at position: {}", position);
+    }
+}

src/lib.rs

@@ -178,6 +178,9 @@
 ///
 pub use stecs_derive::SplitFields;
 
+// TODO: docs
+pub use stecs_derive::World;
+
 /// Get components of a specific entity.
 ///
 /// Syntax is identical to [`query!`], with an additional `id` argument right after the archetype.
@@ -291,6 +294,6 @@ pub mod prelude {
         archetype::{Archetype, StructOf},
         get, query,
         storage::{IdGenerator, Storage},
-        SplitFields,
+        SplitFields, World,
     };
 }