Add derive macro

Cargo.toml

@@ -3,7 +3,7 @@ name = "bevy_enhanced_input"
 version = "0.1.0"
 authors = ["Hennadii Chernyshchyk <[email protected]>"]
 edition = "2021"
-description = "Dynamic and contextual input mappings for Bevy "
+description = "Dynamic and contextual input mappings for Bevy"
 readme = "README.md"
 repository = "https://github.com/projectharmonia/bevy_enhanced_input"
 keywords = ["bevy", "input"]
@@ -12,6 +12,7 @@ license = "MIT OR Apache-2.0"
 include = ["/src", "/tests", "/LICENSE*"]
 
 [dependencies]
+bevy_enhanced_input_macros = { path = "macros" }
 bevy = { version = "0.14", default-features = false, features = ["serialize"] }
 bevy_egui = { version = "0.30", default-features = false, features = [
   "immutable_ctx", # Require to get read-only access in our exclusive system.
@@ -34,3 +35,6 @@ ui_priority = ['bevy/bevy_ui']
 
 # Prioritizes 'egui' over actions when processing inputs.
 egui_priority = ['dep:bevy_egui']
+
+[workspace]
+members = ["macros"]

examples/minimal.rs

@@ -31,27 +31,18 @@ impl InputContext for OnFoot {
     }
 }
 
-#[derive(Debug)]
+#[derive(Debug, InputAction)]
+#[action_dim(Axis2D)]
 struct Walk;
 
-impl InputAction for Walk {
-    const DIM: ActionValueDim = ActionValueDim::Axis2D;
-}
-
-#[derive(Debug)]
+#[derive(Debug, InputAction)]
+#[action_dim(Bool)]
 struct Jump;
 
-impl InputAction for Jump {
-    const DIM: ActionValueDim = ActionValueDim::Bool;
-}
-
-#[derive(Debug)]
+#[derive(Debug, InputAction)]
+#[action_dim(Bool)]
 struct EnterCar;
 
-impl InputAction for EnterCar {
-    const DIM: ActionValueDim = ActionValueDim::Bool;
-}
-
 #[derive(Component)]
 struct InCar;
 
@@ -66,20 +57,14 @@ impl InputContext for InCar {
     }
 }
 
-#[derive(Debug)]
+#[derive(Debug, InputAction)]
+#[action_dim(Axis2D)]
 struct Drive;
 
-impl InputAction for Drive {
-    const DIM: ActionValueDim = ActionValueDim::Axis2D;
-}
-
-#[derive(Debug)]
+#[derive(Debug, InputAction)]
+#[action_dim(Bool)]
 struct ExitCar;
 
-impl InputAction for ExitCar {
-    const DIM: ActionValueDim = ActionValueDim::Bool;
-}
-
 fn spawn(mut commands: Commands) {
     commands.spawn(OnFoot);
 }

macros/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+name = "bevy_enhanced_input_macros"
+version = "0.1.0"
+description = "Bevy Enhanced Input Macros"
+edition = "2021"
+license = "MIT OR Apache-2.0"
+
+[lib]
+proc-macro = true
+
+[dependencies]
+syn = { version = "2.0", features = ["full"] }
+quote = "1.0"
+proc-macro2 = "1.0"

macros/src/lib.rs

@@ -0,0 +1,50 @@
+use proc_macro::TokenStream;
+use proc_macro2::TokenTree;
+use quote::quote;
+use syn::{parse_macro_input, DeriveInput, Meta};
+
+#[proc_macro_derive(InputAction, attributes(action_dim))]
+pub fn input_action_derive(item: TokenStream) -> TokenStream {
+    let input = parse_macro_input!(item as DeriveInput);
+
+    const ATTR_NAME: &str = "action_dim";
+    let mut dim = None;
+    for attr in input.attrs {
+        let Meta::List(list) = attr.meta else {
+            continue;
+        };
+
+        if list
+            .path
+            .segments
+            .iter()
+            .any(|segment| segment.ident == ATTR_NAME)
+        {
+            assert!(dim.is_none(), "`{ATTR_NAME}` can be defined only once");
+
+            let mut token_iter = list.tokens.into_iter();
+            let token = token_iter
+                .next()
+                .unwrap_or_else(|| panic!("`{ATTR_NAME}` should have argument"));
+
+            let TokenTree::Ident(indent) = token else {
+                panic!("`{token}` is invalid argument for `{ATTR_NAME}`");
+            };
+
+            dim = Some(indent);
+
+            assert!(
+                token_iter.next().is_none(),
+                "`{ATTR_NAME}` should have only a single argument"
+            );
+        }
+    }
+
+    let dim = dim.unwrap_or_else(|| panic!("`InputAction` should have `{ATTR_NAME}` attribute"));
+    let struct_name = input.ident;
+    TokenStream::from(quote! {
+        impl InputAction for #struct_name {
+            const DIM: ActionValueDim = ActionValueDim::#dim;
+        }
+    })
+}

src/lib.rs

@@ -16,6 +16,7 @@ pub mod prelude {
         input_reader::KeyboardModifiers,
         EnhancedInputPlugin,
     };
+    pub use bevy_enhanced_input_macros::InputAction;
 }
 
 use bevy::{ecs::system::SystemState, input::InputSystem, prelude::*};