#[derive(Property, Export)] for enums

godot-macros/src/derive_export.rs

@@ -0,0 +1,77 @@
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+use proc_macro2::TokenStream as TokenStream2;
+use quote::quote;
+use venial::{Declaration, StructFields};
+
+use crate::util::{bail, decl_get_info, DeclInfo};
+use crate::ParseResult;
+
+pub fn transform(decl: Declaration) -> ParseResult<TokenStream2> {
+    let DeclInfo { name, .. } = decl_get_info(&decl);
+
+    let enum_ = match decl {
+        Declaration::Enum(e) => e,
+        Declaration::Struct(s) => {
+            return bail!(s.tk_struct, "Export can only be derived on enums for now")
+        }
+        Declaration::Union(u) => {
+            return bail!(u.tk_union, "Export can only be derived on enums for now")
+        }
+        _ => unreachable!(),
+    };
+
+    let hint_string = if enum_.variants.is_empty() {
+        return bail!(
+            enum_.name,
+            "In order to derive Export, enums must have at least one variant"
+        );
+    } else {
+        let mut hint_string_segments = Vec::new();
+        for (enum_v, _) in enum_.variants.inner.iter() {
+            let v_name = enum_v.name.clone();
+            let v_disc = if let Some(c) = enum_v.value.clone() {
+                c.value
+            } else {
+                return bail!(
+                    v_name,
+                    "Property can only be derived on enums with explicit discriminants in all their variants"
+                );
+            };
+            let v_disc_trimmed = v_disc
+                .to_string()
+                .trim_matches(['(', ')'].as_slice())
+                .to_string();
+
+            hint_string_segments.push(format!("{v_name}:{v_disc_trimmed}"));
+
+            match &enum_v.contents {
+                StructFields::Unit => {}
+                _ => {
+                    return bail!(
+                        v_name,
+                        "Property can only be derived on enums with only unit variants for now"
+                    )
+                }
+            };
+        }
+        hint_string_segments.join(",")
+    };
+
+    let out = quote! {
+        #[allow(unused_parens)]
+        impl godot::bind::property::Export for #name {
+            fn default_export_info() -> godot::bind::property::ExportInfo {
+                godot::bind::property::ExportInfo {
+                    hint: godot::engine::global::PropertyHint::PROPERTY_HINT_ENUM,
+                    hint_string: godot::prelude::GodotString::from(#hint_string),
+                }
+            }
+        }
+    };
+    Ok(out)
+}

godot-macros/src/derive_property.rs

@@ -0,0 +1,121 @@
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+use proc_macro2::TokenStream as TokenStream2;
+use quote::{quote, ToTokens};
+use venial::{Declaration, StructFields};
+
+use crate::util::{bail, decl_get_info, ident, DeclInfo};
+use crate::ParseResult;
+
+pub fn transform(decl: Declaration) -> ParseResult<TokenStream2> {
+    let DeclInfo {
+        name, name_string, ..
+    } = decl_get_info(&decl);
+
+    let body_get;
+    let body_set;
+    let intermediate;
+
+    let enum_ = match decl {
+        Declaration::Enum(e) => e,
+        Declaration::Struct(s) => {
+            return bail!(s.tk_struct, "Property can only be derived on enums for now")
+        }
+        Declaration::Union(u) => {
+            return bail!(u.tk_union, "Property can only be derived on enums for now")
+        }
+        _ => unreachable!(),
+    };
+
+    if enum_.variants.is_empty() {
+        return bail!(
+            enum_.name,
+            "In order to derive Property, enums must have at least one variant"
+        );
+    } else {
+        let mut matches_get = quote! {};
+        let mut matches_set = quote! {};
+        intermediate = if let Some(attr) = enum_
+            .attributes
+            .iter()
+            .find(|attr| attr.get_single_path_segment() == Some(&ident("repr")))
+        {
+            attr.value.to_token_stream()
+        } else {
+            return bail!(
+                name,
+                "Property can only be derived on enums with an explicit `#[repr(i*/u*)]` type"
+            );
+        };
+
+        for (enum_v, _) in enum_.variants.inner.iter() {
+            let v_name = enum_v.name.clone();
+            let v_disc = if let Some(c) = enum_v.value.clone() {
+                c.value
+            } else {
+                return bail!(
+                    v_name,
+                    "Property can only be derived on enums with explicit discriminants in all their variants"
+                );
+            };
+
+            let match_content_get;
+            let match_content_set;
+            match &enum_v.contents {
+                StructFields::Unit => {
+                    match_content_get = quote! {
+                        Self::#v_name => #v_disc,
+                    };
+                    match_content_set = quote! {
+                        #v_disc => Self::#v_name,
+                    };
+                }
+                _ => {
+                    return bail!(
+                        v_name,
+                        "Property can only be derived on enums with only unit variants for now"
+                    )
+                }
+            };
+            matches_get = quote! {
+                #matches_get
+                #match_content_get
+            };
+            matches_set = quote! {
+                #matches_set
+                #match_content_set
+            };
+        }
+        body_get = quote! {
+            match &self {
+                #matches_get
+            }
+        };
+        body_set = quote! {
+            *self = match value {
+                #matches_set
+                _ => panic!("Incorrect conversion from {} to {}", stringify!(#intermediate), #name_string),
+            }
+        };
+    }
+
+    let out = quote! {
+        #[allow(unused_parens)]
+        impl godot::bind::property::Property for #name {
+            type Intermediate = #intermediate;
+
+            fn get_property(&self) -> #intermediate {
+                #body_get
+            }
+
+            fn set_property(&mut self, value: #intermediate) {
+                #body_set
+            }
+        }
+    };
+    Ok(out)
+}

godot-macros/src/lib.rs

@@ -87,8 +87,10 @@ use proc_macro2::TokenStream as TokenStream2;
 use quote::quote;
 use venial::Declaration;
 
+mod derive_export;
 mod derive_from_variant;
 mod derive_godot_class;
+mod derive_property;
 mod derive_to_variant;
 mod gdextension;
 mod godot_api;
@@ -454,6 +456,57 @@ pub fn derive_from_variant(input: TokenStream) -> TokenStream {
     translate(input, derive_from_variant::transform)
 }
 
+/// Derive macro for [Property](godot::bind::property::Property) on enums.
+///
+/// Currently has some tight requirements which are expected to be softened as implementation expands:
+/// - Only works for enums, structs aren't supported by this derive macro at the moment.
+/// - The enum must have an explicit `#[repr(u*/i*)]` type.
+///     - This will likely stay this way, since `isize`, the default repr type, is not a concept in Godot.
+/// - The enum variants must not have any fields - currently only unit variants are supported.
+/// - The enum variants must have explicit discriminants, that is, e.g. `A = 2`, not just `A`
+///
+/// # Example
+///
+/// ```no_run
+/// # use godot::prelude::*;
+/// #[repr(i32)]
+/// #[derive(Property)]
+/// # #[derive(PartialEq, Eq, Debug)]
+/// enum TestEnum {
+///     A = 0,
+///     B = 1,
+/// }
+///
+/// #[derive(GodotClass)]
+/// struct TestClass {
+///     #[var]
+///     foo: TestEnum
+/// }
+///
+/// # //TODO: remove this when https://github.com/godot-rust/gdext/issues/187 is truly addressed
+/// # #[godot_api]
+/// # impl TestClass {}
+///
+/// # fn main() {
+/// let mut class = TestClass {foo: TestEnum::B};
+/// assert_eq!(class.get_foo(), TestEnum::B as i32);
+/// class.set_foo(TestEnum::A as i32);
+/// assert_eq!(class.foo, TestEnum::A);
+/// # }
+/// ```
+#[proc_macro_derive(Property)]
+pub fn derive_property(input: TokenStream) -> TokenStream {
+    translate(input, derive_property::transform)
+}
+
+/// Derive macro for [Export](godot::bind::property::Property) on enums.
+///
+/// Currently has some tight requirements which are expected to be softened as implementation expands, see requirements for [Property]
+#[proc_macro_derive(Export)]
+pub fn derive_export(input: TokenStream) -> TokenStream {
+    translate(input, derive_export::transform)
+}
+
 #[proc_macro_attribute]
 pub fn godot_api(_meta: TokenStream, input: TokenStream) -> TokenStream {
     translate(input, godot_api::transform)

godot/src/lib.rs

@@ -169,7 +169,7 @@ pub mod init {
 /// Export user-defined classes and methods to be called by the engine.
 pub mod bind {
     pub use godot_core::property;
-    pub use godot_macros::{godot_api, FromVariant, GodotClass, ToVariant};
+    pub use godot_macros::{godot_api, Export, FromVariant, GodotClass, Property, ToVariant};
 }
 
 /// Testing facilities (unstable).
@@ -184,7 +184,7 @@ pub use godot_core::private;
 /// Often-imported symbols.
 pub mod prelude {
     pub use super::bind::property::{Export, Property, TypeStringHint};
-    pub use super::bind::{godot_api, FromVariant, GodotClass, ToVariant};
+    pub use super::bind::{godot_api, Export, FromVariant, GodotClass, Property, ToVariant};
 
     pub use super::builtin::math::FloatExt as _;
     pub use super::builtin::*;

itest/rust/src/property_test.rs

@@ -8,6 +8,7 @@ use godot::{
     bind::property::ExportInfo,
     engine::{global::PropertyHint, Texture},
     prelude::*,
+    test::itest,
 };
 
 // No tests currently, tests using these classes are in Godot scripts.
@@ -293,3 +294,77 @@ struct CheckAllExports {
 
 #[godot_api]
 impl CheckAllExports {}
+
+#[repr(i64)]
+#[derive(Property, Debug, PartialEq, Eq, Export)]
+pub enum TestEnum {
+    A = 0,
+    B = 1,
+    C = 2,
+}
+
+#[derive(GodotClass)]
+pub struct DeriveProperty {
+    #[var]
+    pub foo: TestEnum,
+}
+
+#[godot_api]
+impl DeriveProperty {}
+
+#[itest]
+fn derive_property() {
+    let mut class = DeriveProperty { foo: TestEnum::B };
+    assert_eq!(class.get_foo(), TestEnum::B as i64);
+    class.set_foo(TestEnum::C as i64);
+    assert_eq!(class.foo, TestEnum::C);
+}
+
+#[derive(GodotClass)]
+pub struct DeriveExport {
+    #[export]
+    pub foo: TestEnum,
+
+    #[base]
+    pub base: Base<RefCounted>,
+}
+
+#[godot_api]
+impl DeriveExport {}
+
+#[godot_api]
+impl RefCountedVirtual for DeriveExport {
+    fn init(base: godot::obj::Base<Self::Base>) -> Self {
+        Self {
+            foo: TestEnum::B,
+            base,
+        }
+    }
+}
+
+#[itest]
+fn derive_export() {
+    let class: Gd<DeriveExport> = Gd::new_default();
+
+    let property = class
+        .get_property_list()
+        .iter_shared()
+        .find(|c| c.get_or_nil("name") == "foo".to_variant())
+        .unwrap();
+    assert_eq!(
+        property.get_or_nil("class_name"),
+        "DeriveExport".to_variant()
+    );
+    assert_eq!(
+        property.get_or_nil("type"),
+        (VariantType::Int as i32).to_variant()
+    );
+    assert_eq!(
+        property.get_or_nil("hint"),
+        (PropertyHint::PROPERTY_HINT_ENUM.ord()).to_variant()
+    );
+    assert_eq!(
+        property.get_or_nil("hint_string"),
+        "A:0,B:1,C:2".to_variant()
+    );
+}