[refactor]: Add compile-time assertions if #[view(into = Type)] is mi…

…ssed

Signed-off-by: Shanin Roman <[email protected]>

config/base/derive/src/lib.rs

@@ -622,11 +622,15 @@ pub fn view(input: TokenStream) -> TokenStream {
     let view = gen_view_struct(ast);
     let impl_from = gen_impl_from(&original, &view);
     let impl_default = gen_impl_default(&original, &view);
+    let impl_has_view = gen_impl_has_view(&original);
+    let assertions = gen_assertions(&view);
     let out = quote! {
         #original
+        #impl_has_view
         #view
         #impl_from
         #impl_default
+        #assertions
     };
     out.into()
 }
@@ -741,6 +745,39 @@ fn gen_impl_default(original: &ViewInput, view: &ViewInput) -> proc_macro2::Toke
     }
 }
 
+fn gen_impl_has_view(original: &ViewInput) -> proc_macro2::TokenStream {
+    let ViewInput {
+        generics,
+        ident: view_ident,
+        ..
+    } = original;
+    let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
+
+    quote! {
+        impl #impl_generics iroha_config_base::view::HasView for #view_ident #ty_generics #where_clause {}
+    }
+}
+
+fn gen_assertions(view: &ViewInput) -> proc_macro2::TokenStream {
+    let ViewInput { fields, .. } = view;
+    let field_types = extract_field_types(fields);
+    let messages: Vec<String> = extract_field_idents(fields)
+        .iter()
+        .map(|ident| {
+            format!("Field `{ident}` has it's own view, consider adding attribute #[view(into = ViewType)]")
+        })
+        .collect();
+    quote! {
+        /// Assert that every field of 'View' doesn't implement `HasView` trait
+        const _: () = {
+            use iroha_config_base::view::NoView;
+            #(
+                const _: () = assert!(!iroha_config_base::view::IsHasView::<#field_types>::IS_HAS_VIEW, #messages);
+            )*
+        };
+    }
+}
+
 /// Change [`Field`] type to `Type` if `#[view(type = Type)]` is present
 fn view_field_change_type(field: &mut Field) {
     if let Some(ty) = field
@@ -791,3 +828,8 @@ fn extract_field_idents(fields: &[Field]) -> Vec<&Ident> {
         })
         .collect::<Vec<_>>()
 }
+
+/// Return [`Vec`] of fields types
+fn extract_field_types(fields: &[Field]) -> Vec<&Type> {
+    fields.iter().map(|field| &field.ty).collect::<Vec<_>>()
+}

config/base/src/lib.rs

@@ -232,3 +232,27 @@ pub trait Configurable: Serialize + DeserializeOwned {
     /// Get inner documentation for non-leaf fields
     fn get_inner_docs() -> String;
 }
+
+pub mod view {
+    //! Module for view related traits and structs
+
+    /// Marker trait to set default value `IS_HAS_VIEW` to `false`
+    pub trait NoView {
+        /// [`Self`] doesn't implement [`HasView`]
+        const IS_HAS_VIEW: bool = false;
+    }
+    impl<T> NoView for T {}
+
+    /// Marker traits for types for which views are implemented  
+    pub trait HasView {}
+
+    /// Wrapper structure used to check if type implements `[HasView]`
+    /// If `T` doesn't implement [`HasView`] then `NoView::IS_HAS_VIEW` (`false`) will be used
+    /// Otherwise `IsHasView::IS_HAS_VIEW` (`true`) from `impl` block will shadow `NoView::IS_HAS_VIEW`  
+    pub struct IsHasView<T>(std::marker::PhantomData<T>);
+
+    impl<T: HasView> IsHasView<T> {
+        /// `T` implements trait [`HasView`]
+        pub const IS_HAS_VIEW: bool = true;
+    }
+}