refactor(ast): #[content_eq(skip)] attr (#8875)

Introduce custom attribute `#[content_eq(skip)]` to guide code generation for `ContentEq` trait. Instead of a hard-coded list of types to skip in codegen, use this attribute on types to control the behavior.

Author: overlookmotel

crates/oxc_ast_macros/src/lib.rs

@@ -47,7 +47,10 @@ pub fn ast(_args: TokenStream, input: TokenStream) -> TokenStream {
 /// Its only purpose is to allow the occurrence of helper attributes used in `tasks/ast_tools`.
 ///
 /// See [`macro@ast`] for further details.
-#[proc_macro_derive(Ast, attributes(clone_in, estree, generate_derive, scope, span, ts, visit))]
+#[proc_macro_derive(
+    Ast,
+    attributes(clone_in, content_eq, estree, generate_derive, scope, span, ts, visit)
+)]
 pub fn ast_derive(_input: TokenStream) -> TokenStream {
     TokenStream::new()
 }

crates/oxc_span/src/span/types.rs

@@ -61,6 +61,7 @@ use super::PointerAlign;
 #[ast(visit)]
 #[derive(Default, Clone, Copy, Eq, PartialOrd, Ord)]
 #[generate_derive(ESTree)]
+#[content_eq(skip)]
 #[estree(no_type, flatten)]
 pub struct Span {
     /// The zero-based start offset of the span

crates/oxc_syntax/src/reference.rs

@@ -1,17 +1,19 @@
 #![allow(missing_docs)] // fixme
 use bitflags::bitflags;
 use nonmax::NonMaxU32;
-use oxc_allocator::CloneIn;
 use oxc_index::Idx;
 #[cfg(feature = "serialize")]
 use serde::{Serialize, Serializer};
 
+use oxc_allocator::CloneIn;
+
 use crate::{node::NodeId, symbol::SymbolId};
 
 use oxc_ast_macros::ast;
 
 #[ast]
 #[derive(Debug, Clone, Copy, Eq, PartialEq, Ord, PartialOrd, Hash)]
+#[content_eq(skip)]
 pub struct ReferenceId(NonMaxU32);
 
 impl Idx for ReferenceId {

crates/oxc_syntax/src/scope.rs

@@ -9,6 +9,7 @@ use oxc_ast_macros::ast;
 
 #[ast]
 #[derive(Debug, Clone, Copy, Eq, PartialEq, Ord, PartialOrd, Hash)]
+#[content_eq(skip)]
 pub struct ScopeId(NonMaxU32);
 
 impl ScopeId {

crates/oxc_syntax/src/symbol.rs

@@ -9,6 +9,7 @@ use oxc_ast_macros::ast;
 
 #[ast]
 #[derive(Debug, Clone, Copy, Eq, PartialEq, Ord, PartialOrd, Hash)]
+#[content_eq(skip)]
 pub struct SymbolId(NonMaxU32);
 
 impl SymbolId {

tasks/ast_tools/src/derives/content_eq.rs

@@ -3,11 +3,14 @@
 use proc_macro2::TokenStream;
 use quote::{format_ident, quote};
 
-use crate::schema::{Def, EnumDef, Schema, StructDef};
+use crate::{
+    schema::{Def, EnumDef, Schema, StructDef, TypeDef},
+    Result,
+};
 
-use super::{define_derive, Derive, StructOrEnum};
-
-const IGNORE_FIELD_TYPES: [&str; 4] = ["Span", "ScopeId", "SymbolId", "ReferenceId"];
+use super::{
+    attr_positions, define_derive, AttrLocation, AttrPart, AttrPositions, Derive, StructOrEnum,
+};
 
 /// Derive for `ContentEq` trait.
 pub struct DeriveContentEq;
@@ -23,6 +26,31 @@ impl Derive for DeriveContentEq {
         "oxc_span"
     }
 
+    /// Register that accept `#[content_eq]` attr on structs, enums, or struct fields.
+    /// Allow attr on structs and enums which don't derive this trait.
+    fn attrs(&self) -> &[(&'static str, AttrPositions)] {
+        &[("content_eq", attr_positions!(StructMaybeDerived | EnumMaybeDerived | StructField))]
+    }
+
+    /// Parse `#[content_eq(skip)]` attr.
+    fn parse_attr(&self, _attr_name: &str, location: AttrLocation, part: AttrPart) -> Result<()> {
+        // No need to check attr name is `content_eq`, because that's the only attribute this derive handles.
+        if !matches!(part, AttrPart::Tag("skip")) {
+            return Err(());
+        }
+
+        match location {
+            AttrLocation::Struct(struct_def) => struct_def.content_eq.skip = true,
+            AttrLocation::Enum(enum_def) => enum_def.content_eq.skip = true,
+            AttrLocation::StructField(struct_def, field_index) => {
+                struct_def.fields[field_index].content_eq.skip = true;
+            }
+            _ => return Err(()),
+        }
+
+        Ok(())
+    }
+
     fn prelude(&self) -> TokenStream {
         quote! {
             #![allow(clippy::match_same_arms)]
@@ -41,30 +69,49 @@ impl Derive for DeriveContentEq {
 }
 
 fn derive_struct(struct_def: &StructDef, schema: &Schema) -> TokenStream {
-    let fields = struct_def
-        .fields
-        .iter()
-        .filter(|field| {
-            let innermost_type = field.type_def(schema).innermost_type(schema);
-            !IGNORE_FIELD_TYPES.contains(&innermost_type.name())
-        })
-        .map(|field| {
-            let ident = field.ident();
-            quote!( ContentEq::content_eq(&self.#ident, &other.#ident) )
-        });
-
-    let mut body = quote!( #(#fields)&&* );
     let mut other_name = "other";
-    if body.is_empty() {
-        body = quote!(true);
+
+    let body = if struct_def.content_eq.skip {
+        // Struct has `#[content_eq(skip)]` attr. So `content_eq` always returns true.
         other_name = "_";
+        quote!(true)
+    } else {
+        let fields = struct_def
+            .fields
+            .iter()
+            .filter(|field| !field.content_eq.skip)
+            .filter(|field| {
+                let innermost_type = field.type_def(schema).innermost_type(schema);
+                match innermost_type {
+                    TypeDef::Struct(struct_def) => !struct_def.content_eq.skip,
+                    TypeDef::Enum(enum_def) => !enum_def.content_eq.skip,
+                    _ => true,
+                }
+            })
+            .map(|field| {
+                let ident = field.ident();
+                quote!( ContentEq::content_eq(&self.#ident, &other.#ident) )
+            });
+
+        let mut body = quote!( #(#fields)&&* );
+        if body.is_empty() {
+            body = quote!(true);
+            other_name = "_";
+        };
+        body
     };
 
     generate_impl(&struct_def.ty_anon(schema), other_name, &body)
 }
 
 fn derive_enum(enum_def: &EnumDef, schema: &Schema) -> TokenStream {
-    let body = if enum_def.is_fieldless() {
+    let mut other_name = "other";
+
+    let body = if enum_def.content_eq.skip {
+        // Enum has `#[content_eq(skip)]` attr. So `content_eq` always returns true.
+        other_name = "_";
+        quote!(true)
+    } else if enum_def.is_fieldless() {
         // We assume fieldless enums implement `PartialEq`
         quote!(self == other)
     } else {
@@ -76,6 +123,7 @@ fn derive_enum(enum_def: &EnumDef, schema: &Schema) -> TokenStream {
                 quote!( (Self::#ident(a), Self::#ident(b)) => a.content_eq(b) )
             }
         });
+
         quote! {
             match (self, other) {
                 #(#matches,)*
@@ -84,7 +132,7 @@ fn derive_enum(enum_def: &EnumDef, schema: &Schema) -> TokenStream {
         }
     };
 
-    generate_impl(&enum_def.ty_anon(schema), "other", &body)
+    generate_impl(&enum_def.ty_anon(schema), other_name, &body)
 }
 
 fn generate_impl(ty: &TokenStream, other_name: &str, body: &TokenStream) -> TokenStream {

tasks/ast_tools/src/schema/defs/enum.rs

@@ -9,6 +9,7 @@ use crate::utils::create_ident;
 
 use super::{
     extensions::{
+        content_eq::ContentEqType,
         estree::{ESTreeEnum, ESTreeEnumVariant},
         kind::Kind,
         layout::Layout,
@@ -33,6 +34,7 @@ pub struct EnumDef {
     pub visit: VisitEnum,
     pub kind: Kind,
     pub layout: Layout,
+    pub content_eq: ContentEqType,
     pub estree: ESTreeEnum,
 }
 
@@ -58,6 +60,7 @@ impl EnumDef {
             visit: VisitEnum::default(),
             kind: Kind::default(),
             layout: Layout::default(),
+            content_eq: ContentEqType::default(),
             estree: ESTreeEnum::default(),
         }
     }

tasks/ast_tools/src/schema/defs/struct.rs

@@ -9,6 +9,7 @@ use crate::utils::create_ident_tokens;
 use super::{
     extensions::{
         clone_in::CloneInStructField,
+        content_eq::{ContentEqStructField, ContentEqType},
         estree::{ESTreeStruct, ESTreeStructField},
         kind::Kind,
         layout::{Layout, Offset},
@@ -31,6 +32,7 @@ pub struct StructDef {
     pub kind: Kind,
     pub layout: Layout,
     pub span: SpanStruct,
+    pub content_eq: ContentEqType,
     pub estree: ESTreeStruct,
 }
 
@@ -55,6 +57,7 @@ impl StructDef {
             kind: Kind::default(),
             layout: Layout::default(),
             span: SpanStruct::default(),
+            content_eq: ContentEqType::default(),
             estree: ESTreeStruct::default(),
         }
     }
@@ -118,6 +121,7 @@ pub struct FieldDef {
     pub visit: VisitFieldOrVariant,
     pub offset: Offset,
     pub clone_in: CloneInStructField,
+    pub content_eq: ContentEqStructField,
     pub estree: ESTreeStructField,
 }
 
@@ -137,6 +141,7 @@ impl FieldDef {
             visit: VisitFieldOrVariant::default(),
             offset: Offset::default(),
             clone_in: CloneInStructField::default(),
+            content_eq: ContentEqStructField::default(),
             estree: ESTreeStructField::default(),
         }
     }

tasks/ast_tools/src/schema/extensions/content_eq.rs

@@ -0,0 +1,13 @@
+/// Details for `ContentEq` derive on a struct or enum.
+#[derive(Default, Debug)]
+pub struct ContentEqType {
+    /// `true` if type should ignored by `ContentEq`
+    pub skip: bool,
+}
+
+/// Details for `ContentEq` derive on a struct field.
+#[derive(Default, Debug)]
+pub struct ContentEqStructField {
+    /// `true` if field should ignored by `ContentEq`
+    pub skip: bool,
+}

tasks/ast_tools/src/schema/mod.rs

@@ -14,6 +14,7 @@ pub use file::File;
 /// Extensions to schema for specific derives / generators
 pub mod extensions {
     pub mod clone_in;
+    pub mod content_eq;
     pub mod estree;
     pub mod kind;
     pub mod layout;