bevy_reflect: Allow #[reflect(skip_serializing)] on enum variant fields

crates/bevy_reflect/bevy_reflect_derive/src/derive_data.rs

@@ -1,10 +1,10 @@
 use crate::container_attributes::ReflectTraits;
 use crate::field_attributes::{parse_field_attrs, ReflectFieldAttr};
 use crate::fq_std::{FQAny, FQDefault, FQSend, FQSync};
-use crate::utility::{members_to_serialization_denylist, WhereClauseOptions};
-use bit_set::BitSet;
+use crate::utility::WhereClauseOptions;
 use quote::quote;
 
+use crate::serialization::SerializationDenylist;
 use crate::{utility, REFLECT_ATTRIBUTE_NAME, REFLECT_VALUE_ATTRIBUTE_NAME};
 use syn::punctuated::Punctuated;
 use syn::spanned::Spanned;
@@ -60,7 +60,7 @@ pub(crate) struct ReflectMeta<'a> {
 /// ```
 pub(crate) struct ReflectStruct<'a> {
     meta: ReflectMeta<'a>,
-    serialization_denylist: BitSet<u32>,
+    serialization_denylist: SerializationDenylist,
     fields: Vec<StructField<'a>>,
 }
 
@@ -79,6 +79,7 @@ pub(crate) struct ReflectStruct<'a> {
 /// ```
 pub(crate) struct ReflectEnum<'a> {
     meta: ReflectMeta<'a>,
+    serialization_denylist: SerializationDenylist,
     variants: Vec<EnumVariant<'a>>,
 }
 
@@ -199,8 +200,8 @@ impl<'a> ReflectDerive<'a> {
                 let fields = Self::collect_struct_fields(&data.fields)?;
                 let reflect_struct = ReflectStruct {
                     meta,
-                    serialization_denylist: members_to_serialization_denylist(
-                        fields.iter().map(|v| v.attrs.ignore),
+                    serialization_denylist: SerializationDenylist::from_struct_fields(
+                        fields.iter(),
                     ),
                     fields,
                 };
@@ -214,7 +215,13 @@ impl<'a> ReflectDerive<'a> {
             Data::Enum(data) => {
                 let variants = Self::collect_enum_variants(&data.variants)?;
 
-                let reflect_enum = ReflectEnum { meta, variants };
+                let reflect_enum = ReflectEnum {
+                    meta,
+                    serialization_denylist: SerializationDenylist::from_enum_variants(
+                        variants.iter(),
+                    ),
+                    variants,
+                };
                 Ok(Self::Enum(reflect_enum))
             }
             Data::Union(..) => Err(syn::Error::new(
@@ -345,10 +352,7 @@ impl<'a> ReflectStruct<'a> {
     }
 
     /// Access the data about which fields should be ignored during serialization.
-    ///
-    /// The returned bitset is a collection of indices obtained from the [`members_to_serialization_denylist`](crate::utility::members_to_serialization_denylist) function.
-    #[allow(dead_code)]
-    pub fn serialization_denylist(&self) -> &BitSet<u32> {
+    pub fn serialization_denylist(&self) -> &SerializationDenylist {
         &self.serialization_denylist
     }
 
@@ -359,15 +363,13 @@ impl<'a> ReflectStruct<'a> {
         &self,
         where_clause_options: &WhereClauseOptions,
     ) -> proc_macro2::TokenStream {
-        let reflect_path = self.meta.bevy_reflect_path();
-
         crate::registration::impl_get_type_registration(
             self.meta.type_name(),
-            reflect_path,
+            self.meta.bevy_reflect_path(),
             self.meta.traits().idents(),
             self.meta.generics(),
             where_clause_options,
-            Some(&self.serialization_denylist),
+            Some(self.serialization_denylist()),
         )
     }
 
@@ -430,6 +432,11 @@ impl<'a> ReflectEnum<'a> {
         }
     }
 
+    /// Access the data about which fields should be ignored during serialization.
+    pub fn serialization_denylist(&self) -> &SerializationDenylist {
+        &self.serialization_denylist
+    }
+
     /// The complete set of variants in this enum.
     pub fn variants(&self) -> &[EnumVariant<'a>] {
         &self.variants
@@ -472,6 +479,23 @@ impl<'a> ReflectEnum<'a> {
             ignored_trait_bounds: quote! { #FQAny + #FQSend + #FQSync + #FQDefault },
         }
     }
+
+    /// Returns the `GetTypeRegistration` impl as a `TokenStream`.
+    ///
+    /// Returns a specific implementation for enums that should be preferred over the generic [`get_type_registration`](crate::ReflectMeta) method.
+    pub fn get_type_registration(
+        &self,
+        where_clause_options: &WhereClauseOptions,
+    ) -> proc_macro2::TokenStream {
+        crate::registration::impl_get_type_registration(
+            self.meta.type_name(),
+            self.meta.bevy_reflect_path(),
+            self.meta.traits().idents(),
+            self.meta.generics(),
+            where_clause_options,
+            Some(self.serialization_denylist()),
+        )
+    }
 }
 
 impl<'a> EnumVariant<'a> {

crates/bevy_reflect/bevy_reflect_derive/src/impls/enums.rs

@@ -88,9 +88,8 @@ pub(crate) fn impl_enum(reflect_enum: &ReflectEnum) -> TokenStream {
         bevy_reflect_path,
     );
 
-    let get_type_registration_impl = reflect_enum
-        .meta()
-        .get_type_registration(&where_clause_options);
+    let get_type_registration_impl = reflect_enum.get_type_registration(&where_clause_options);
+
     let (impl_generics, ty_generics, where_clause) =
         reflect_enum.meta().generics().split_for_impl();
 

crates/bevy_reflect/bevy_reflect_derive/src/lib.rs

@@ -25,6 +25,7 @@ mod from_reflect;
 mod impls;
 mod reflect_value;
 mod registration;
+mod serialization;
 mod trait_reflection;
 mod type_uuid;
 mod utility;

crates/bevy_reflect/bevy_reflect_derive/src/registration.rs

@@ -1,9 +1,9 @@
 //! Contains code related specifically to Bevy's type registration.
 
+use crate::serialization::SerializationDenylist;
 use crate::utility::{extend_where_clause, WhereClauseOptions};
-use bit_set::BitSet;
 use proc_macro2::Ident;
-use quote::quote;
+use quote::{quote, ToTokens};
 use syn::{Generics, Path};
 
 /// Creates the `GetTypeRegistration` impl for the given type data.
@@ -14,14 +14,47 @@ pub(crate) fn impl_get_type_registration(
     registration_data: &[Ident],
     generics: &Generics,
     where_clause_options: &WhereClauseOptions,
-    serialization_denylist: Option<&BitSet<u32>>,
+    serialization_denylist: Option<&SerializationDenylist>,
 ) -> proc_macro2::TokenStream {
     let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
-    let serialization_data = serialization_denylist.map(|denylist| {
-        let denylist = denylist.into_iter();
-        quote! {
-            let ignored_indices = ::core::iter::IntoIterator::into_iter([#(#denylist),*]);
-            registration.insert::<#bevy_reflect_path::serde::SerializationData>(#bevy_reflect_path::serde::SerializationData::new(ignored_indices));
+
+    let serialization_data = serialization_denylist.map(|denylist| match denylist {
+        SerializationDenylist::Struct(denylist) => {
+            let denylist = denylist.into_iter();
+            quote! {
+                let ignored_indices = ::core::iter::IntoIterator::into_iter([#(#denylist),*]);
+                registration.insert(
+                    #bevy_reflect_path::serde::SerializationData::Struct(
+                        #bevy_reflect_path::serde::StructSerializationData::new(ignored_indices)
+                    )
+                );
+            }
+        }
+        SerializationDenylist::Enum(denylist) => {
+            // This will contain a list of tuples containing:
+            // 1. The name of the variant
+            // 2. An iterator of the skipped indices
+            let mut indices = proc_macro2::TokenStream::new();
+            for (variant_name, variant_fields) in denylist {
+                let variant_fields = variant_fields.into_iter();
+                quote!((
+                    #variant_name,
+                    ::core::iter::Iterator::copied(
+                        ::core::iter::IntoIterator::into_iter(
+                            &[#(#variant_fields),*] as &[usize]
+                        )
+                    )
+                ),)
+                .to_tokens(&mut indices);
+            }
+            quote! {
+                let ignored_indices = ::core::iter::IntoIterator::into_iter([#indices]);
+                registration.insert(
+                    #bevy_reflect_path::serde::SerializationData::Enum(
+                        #bevy_reflect_path::serde::EnumSerializationData::new(ignored_indices)
+                    )
+                );
+            }
         }
     });
 

crates/bevy_reflect/bevy_reflect_derive/src/serialization.rs

@@ -0,0 +1,76 @@
+use crate::derive_data::{EnumVariant, StructField};
+use crate::field_attributes::ReflectIgnoreBehavior;
+use bit_set::BitSet;
+
+/// A bitset of fields to ignore for serialization.
+///
+/// This uses the `#[reflect(skip_serializing)]` and `#[reflect(ignore)]` attributes to determine
+/// which fields to mark as skippable for serialization.
+///
+/// This data is encoded into a bitset over the fields' indices.
+///
+/// For enums, this also contains the name of the variant associated with the bitset.
+pub(crate) enum SerializationDenylist {
+    Struct(BitSet<usize>),
+    Enum(Vec<(String, BitSet<usize>)>),
+}
+
+impl SerializationDenylist {
+    /// Create a new bitset for a struct's fields.
+    ///
+    /// This will return a [`SerializationDenylist::Struct`] value.
+    pub fn from_struct_fields<'a>(fields: impl Iterator<Item = &'a StructField<'a>>) -> Self {
+        Self::Struct(Self::generate_bitset(fields))
+    }
+
+    /// Create a new bitset for an enum's fields.
+    ///
+    /// This will return a [`SerializationDenylist::Enum`] value.
+    pub fn from_enum_variants<'a>(variants: impl Iterator<Item = &'a EnumVariant<'a>>) -> Self {
+        Self::Enum(
+            variants
+                .map(|variant| {
+                    let name = variant.data.ident.to_string();
+                    let denylist = Self::generate_bitset(variant.fields().iter());
+                    (name, denylist)
+                })
+                .collect(),
+        )
+    }
+
+    /// Converts an iterator over fields to a bitset of ignored members.
+    ///
+    /// Takes into account the fact that always ignored (non-reflected) members are skipped.
+    ///
+    /// # Example
+    /// ```rust,ignore
+    /// pub struct HelloWorld {
+    ///     reflected_field: u32      // index: 0
+    ///
+    ///     #[reflect(ignore)]
+    ///     non_reflected_field: u32  // index: N/A (not 1!)
+    ///
+    ///     #[reflect(skip_serializing)]
+    ///     non_serialized_field: u32 // index: 1
+    /// }
+    /// ```
+    /// Would convert to the `0b01` bitset (i.e second field is NOT serialized).
+    /// Keep in mind, however, that it is always recommended that
+    /// `#[reflect(skip_serializing)]` comes _before_ `#[reflect(ignore)]`.
+    /// The example above is meant for demonstration purposes only.
+    ///
+    fn generate_bitset<'a>(fields: impl Iterator<Item = &'a StructField<'a>>) -> BitSet<usize> {
+        let mut bitset = BitSet::default();
+
+        fields.fold(0, |next_idx, member| match member.attrs.ignore {
+            ReflectIgnoreBehavior::IgnoreAlways => next_idx,
+            ReflectIgnoreBehavior::IgnoreSerialization => {
+                bitset.insert(next_idx);
+                next_idx + 1
+            }
+            ReflectIgnoreBehavior::None => next_idx + 1,
+        });
+
+        bitset
+    }
+}

crates/bevy_reflect/bevy_reflect_derive/src/utility.rs

@@ -1,8 +1,6 @@
 //! General-purpose utility functions for internal usage within this crate.
 
-use crate::field_attributes::ReflectIgnoreBehavior;
 use bevy_macro_utils::BevyManifest;
-use bit_set::BitSet;
 use proc_macro2::{Ident, Span};
 use quote::quote;
 use syn::{Member, Path, Type, WhereClause};
@@ -176,39 +174,3 @@ impl<T> ResultSifter<T> {
         }
     }
 }
-
-/// Converts an iterator over ignore behavior of members to a bitset of ignored members.
-///
-/// Takes into account the fact that always ignored (non-reflected) members are skipped.
-///
-/// # Example
-/// ```rust,ignore
-/// pub struct HelloWorld {
-///     reflected_field: u32      // index: 0
-///
-///     #[reflect(ignore)]
-///     non_reflected_field: u32  // index: N/A (not 1!)
-///
-///     #[reflect(skip_serializing)]
-///     non_serialized_field: u32 // index: 1
-/// }
-/// ```
-/// Would convert to the `0b01` bitset (i.e second field is NOT serialized)
-///
-pub(crate) fn members_to_serialization_denylist<T>(member_iter: T) -> BitSet<u32>
-where
-    T: Iterator<Item = ReflectIgnoreBehavior>,
-{
-    let mut bitset = BitSet::default();
-
-    member_iter.fold(0, |next_idx, member| match member {
-        ReflectIgnoreBehavior::IgnoreAlways => next_idx,
-        ReflectIgnoreBehavior::IgnoreSerialization => {
-            bitset.insert(next_idx);
-            next_idx + 1
-        }
-        ReflectIgnoreBehavior::None => next_idx + 1,
-    });
-
-    bitset
-}