refactor(ast/estree): generalize concatenating fields with Concat2 (#10848)

Pure refactor. Replace `AppendTo` and `AppendToConcat` which are used in ESTree serializer to concatenate 2 fields with a more generalized `Concat2`, which performs both functions.

crates/oxc_allocator/src/vec.rs

@@ -15,7 +15,7 @@ use std::{
 
 use crate::vec2::Vec as InnerVec;
 #[cfg(any(feature = "serialize", test))]
-use oxc_estree::{ESTree, Serializer as ESTreeSerializer};
+use oxc_estree::{ConcatElement, ESTree, SequenceSerializer, Serializer as ESTreeSerializer};
 #[cfg(any(feature = "serialize", test))]
 use serde::{Serialize, Serializer as SerdeSerializer};
 
@@ -248,6 +248,15 @@ impl<T: ESTree> ESTree for Vec<'_, T> {
     }
 }
 
+#[cfg(feature = "serialize")]
+impl<T: ESTree> ConcatElement for Vec<'_, T> {
+    fn push_to_sequence<S: SequenceSerializer>(&self, seq: &mut S) {
+        for element in self {
+            seq.serialize_element(element);
+        }
+    }
+}
+
 impl<T: Hash> Hash for Vec<'_, T> {
     #[inline(always)]
     fn hash<H: Hasher>(&self, state: &mut H) {

crates/oxc_ast/src/generated/derive_estree.rs

@@ -4,8 +4,7 @@
 #![allow(unused_imports, clippy::match_same_arms, clippy::semicolon_if_nothing_returned)]
 
 use oxc_estree::{
-    ESTree, FlatStructSerializer, JsonSafeString, Serializer, StructSerializer,
-    ser::{AppendTo, AppendToConcat},
+    Concat2, ESTree, FlatStructSerializer, JsonSafeString, Serializer, StructSerializer,
 };
 
 use crate::ast::comment::*;
@@ -635,7 +634,7 @@ impl ESTree for ArrayAssignmentTarget<'_> {
         state.serialize_field("type", &JsonSafeString("ArrayPattern"));
         state.serialize_field("start", &self.span.start);
         state.serialize_field("end", &self.span.end);
-        state.serialize_field("elements", &AppendTo { array: &self.elements, after: &self.rest });
+        state.serialize_field("elements", &Concat2(&self.elements, &self.rest));
         state.serialize_ts_field("decorators", &crate::serialize::TsEmptyArray(self));
         state.serialize_ts_field("optional", &crate::serialize::TsFalse(self));
         state.serialize_ts_field("typeAnnotation", &crate::serialize::TsNull(self));
@@ -649,10 +648,7 @@ impl ESTree for ObjectAssignmentTarget<'_> {
         state.serialize_field("type", &JsonSafeString("ObjectPattern"));
         state.serialize_field("start", &self.span.start);
         state.serialize_field("end", &self.span.end);
-        state.serialize_field(
-            "properties",
-            &AppendTo { array: &self.properties, after: &self.rest },
-        );
+        state.serialize_field("properties", &Concat2(&self.properties, &self.rest));
         state.serialize_ts_field("decorators", &crate::serialize::TsEmptyArray(self));
         state.serialize_ts_field("optional", &crate::serialize::TsFalse(self));
         state.serialize_ts_field("typeAnnotation", &crate::serialize::TsNull(self));
@@ -1295,10 +1291,7 @@ impl ESTree for ObjectPattern<'_> {
         state.serialize_field("type", &JsonSafeString("ObjectPattern"));
         state.serialize_field("start", &self.span.start);
         state.serialize_field("end", &self.span.end);
-        state.serialize_field(
-            "properties",
-            &AppendTo { array: &self.properties, after: &self.rest },
-        );
+        state.serialize_field("properties", &Concat2(&self.properties, &self.rest));
         state.serialize_ts_field("decorators", &crate::serialize::TsEmptyArray(self));
         state.serialize_ts_field("optional", &crate::serialize::TsFalse(self));
         state.serialize_ts_field("typeAnnotation", &crate::serialize::TsNull(self));
@@ -1329,7 +1322,7 @@ impl ESTree for ArrayPattern<'_> {
         state.serialize_field("type", &JsonSafeString("ArrayPattern"));
         state.serialize_field("start", &self.span.start);
         state.serialize_field("end", &self.span.end);
-        state.serialize_field("elements", &AppendTo { array: &self.elements, after: &self.rest });
+        state.serialize_field("elements", &Concat2(&self.elements, &self.rest));
         state.serialize_ts_field("decorators", &crate::serialize::TsEmptyArray(self));
         state.serialize_ts_field("optional", &crate::serialize::TsFalse(self));
         state.serialize_ts_field("typeAnnotation", &crate::serialize::TsNull(self));
@@ -1419,10 +1412,7 @@ impl ESTree for FunctionBody<'_> {
         state.serialize_field("type", &JsonSafeString("BlockStatement"));
         state.serialize_field("start", &self.span.start);
         state.serialize_field("end", &self.span.end);
-        state.serialize_field(
-            "body",
-            &AppendToConcat { array: &self.directives, after: &self.statements },
-        );
+        state.serialize_field("body", &Concat2(&self.directives, &self.statements));
         state.end();
     }
 }
@@ -3076,10 +3066,7 @@ impl ESTree for TSModuleBlock<'_> {
         state.serialize_field("type", &JsonSafeString("TSModuleBlock"));
         state.serialize_field("start", &self.span.start);
         state.serialize_field("end", &self.span.end);
-        state.serialize_field(
-            "body",
-            &AppendToConcat { array: &self.directives, after: &self.body },
-        );
+        state.serialize_field("body", &Concat2(&self.directives, &self.body));
         state.end();
     }
 }

crates/oxc_ast/src/serialize.rs

@@ -6,9 +6,9 @@ use crate::ast::*;
 use oxc_ast_macros::ast_meta;
 use oxc_estree::{
     CompactFixesJSSerializer, CompactFixesTSSerializer, CompactJSSerializer, CompactTSSerializer,
-    ESTree, FlatStructSerializer, JsonSafeString, LoneSurrogatesString, PrettyFixesJSSerializer,
-    PrettyFixesTSSerializer, PrettyJSSerializer, PrettyTSSerializer, SequenceSerializer,
-    Serializer, StructSerializer, ser::AppendToConcat,
+    Concat2, ESTree, FlatStructSerializer, JsonSafeString, LoneSurrogatesString,
+    PrettyFixesJSSerializer, PrettyFixesTSSerializer, PrettyJSSerializer, PrettyTSSerializer,
+    SequenceSerializer, Serializer, StructSerializer,
 };
 use oxc_span::GetSpan;
 
@@ -171,10 +171,7 @@ impl ESTree for ProgramConverter<'_, '_> {
         state.serialize_field("type", &JsonSafeString("Program"));
         state.serialize_field("start", &span_start);
         state.serialize_field("end", &program.span.end);
-        state.serialize_field(
-            "body",
-            &AppendToConcat { array: &program.directives, after: &program.body },
-        );
+        state.serialize_field("body", &Concat2(&program.directives, &program.body));
         state.serialize_field("sourceType", &program.source_type.module_kind());
         state.serialize_field("hashbang", &program.hashbang);
         state.end();

crates/oxc_estree/src/lib.rs

@@ -1,6 +1,4 @@
 #[cfg(feature = "serialize")]
-pub mod ser;
-#[cfg(feature = "serialize")]
 mod serialize;
 #[cfg(feature = "serialize")]
 pub use serialize::*;

crates/oxc_estree/src/ser.rs

@@ -1,41 +0,0 @@
-use crate::{ESTree, SequenceSerializer, Serializer};
-
-/// A helper struct for serializing a sequence followed by an optional element.
-/// This is only used by generated ESTree serialization code.
-pub struct AppendTo<'a, TVec, TAfter> {
-    pub array: &'a [TVec],
-    pub after: &'a Option<TAfter>,
-}
-
-impl<TVec: ESTree, TAfter: ESTree> ESTree for AppendTo<'_, TVec, TAfter> {
-    fn serialize<S: Serializer>(&self, serializer: S) {
-        if let Some(after) = self.after {
-            let mut seq = serializer.serialize_sequence();
-            for element in self.array {
-                seq.serialize_element(element);
-            }
-            seq.serialize_element(after);
-            seq.end();
-        } else {
-            self.array.serialize(serializer);
-        }
-    }
-}
-
-pub struct AppendToConcat<'a, TVec, TAfter> {
-    pub array: &'a [TVec],
-    pub after: &'a [TAfter],
-}
-
-impl<TVec: ESTree, TAfter: ESTree> ESTree for AppendToConcat<'_, TVec, TAfter> {
-    fn serialize<S: Serializer>(&self, serializer: S) {
-        let mut seq = serializer.serialize_sequence();
-        for element in self.array {
-            seq.serialize_element(element);
-        }
-        for element in self.after {
-            seq.serialize_element(element);
-        }
-        seq.end();
-    }
-}

crates/oxc_estree/src/serialize/concat.rs

@@ -0,0 +1,28 @@
+use crate::{ESTree, SequenceSerializer, Serializer};
+
+/// Trait for types which can be concatenated.
+///
+/// Implemented by `Option` and `Vec`.
+pub trait ConcatElement {
+    fn push_to_sequence<S: SequenceSerializer>(&self, seq: &mut S);
+}
+
+impl<T: ESTree> ConcatElement for Option<T> {
+    fn push_to_sequence<S: SequenceSerializer>(&self, seq: &mut S) {
+        if let Some(value) = self {
+            seq.serialize_element(value);
+        }
+    }
+}
+
+/// Helper struct for concatenating 2 elements into a sequence.
+pub struct Concat2<'t, C1: ConcatElement, C2: ConcatElement>(pub &'t C1, pub &'t C2);
+
+impl<C1: ConcatElement, C2: ConcatElement> ESTree for Concat2<'_, C1, C2> {
+    fn serialize<S: Serializer>(&self, serializer: S) {
+        let mut seq = serializer.serialize_sequence();
+        self.0.push_to_sequence(&mut seq);
+        self.1.push_to_sequence(&mut seq);
+        seq.end();
+    }
+}

crates/oxc_estree/src/serialize/mod.rs

@@ -8,6 +8,7 @@ use itoa::Buffer as ItoaBuffer;
 use oxc_data_structures::{code_buffer::CodeBuffer, stack::NonEmptyStack};
 
 mod blanket;
+mod concat;
 mod config;
 mod formatter;
 mod primitives;
@@ -19,6 +20,7 @@ use formatter::{CompactFormatter, Formatter, PrettyFormatter};
 use sequences::ESTreeSequenceSerializer;
 use structs::ESTreeStructSerializer;
 
+pub use concat::{Concat2, ConcatElement};
 pub use sequences::SequenceSerializer;
 pub use strings::{JsonSafeString, LoneSurrogatesString};
 pub use structs::{FlatStructSerializer, StructSerializer};

crates/oxc_span/src/generated/derive_estree.rs

@@ -4,8 +4,7 @@
 #![allow(unused_imports, clippy::match_same_arms, clippy::semicolon_if_nothing_returned)]
 
 use oxc_estree::{
-    ESTree, FlatStructSerializer, JsonSafeString, Serializer, StructSerializer,
-    ser::{AppendTo, AppendToConcat},
+    Concat2, ESTree, FlatStructSerializer, JsonSafeString, Serializer, StructSerializer,
 };
 
 use crate::source_type::*;

crates/oxc_syntax/src/generated/derive_estree.rs

@@ -4,8 +4,7 @@
 #![allow(unused_imports, clippy::match_same_arms, clippy::semicolon_if_nothing_returned)]
 
 use oxc_estree::{
-    ESTree, FlatStructSerializer, JsonSafeString, Serializer, StructSerializer,
-    ser::{AppendTo, AppendToConcat},
+    Concat2, ESTree, FlatStructSerializer, JsonSafeString, Serializer, StructSerializer,
 };
 
 use crate::module_record::*;

napi/parser/src/generated/derive_estree.rs

@@ -4,8 +4,7 @@
 #![allow(unused_imports, clippy::match_same_arms, clippy::semicolon_if_nothing_returned)]
 
 use oxc_estree::{
-    ESTree, FlatStructSerializer, JsonSafeString, Serializer, StructSerializer,
-    ser::{AppendTo, AppendToConcat},
+    Concat2, ESTree, FlatStructSerializer, JsonSafeString, Serializer, StructSerializer,
 };
 
 use crate::raw_transfer_types::*;

tasks/ast_tools/src/derives/estree.rs

@@ -71,8 +71,7 @@ impl Derive for DeriveESTree {
 
             ///@@line_break
             use oxc_estree::{
-                ser::{AppendTo, AppendToConcat},
-                ESTree, FlatStructSerializer, JsonSafeString, Serializer, StructSerializer,
+                Concat2, ESTree, FlatStructSerializer, JsonSafeString, Serializer, StructSerializer,
             };
         }
     }
@@ -443,16 +442,9 @@ impl<'s> StructSerializerGenerator<'s> {
             let converter_path = get_converter_path(converter_name, self.krate, self.schema);
             quote!( #converter_path(#self_path) )
         } else if let Some(append_field_index) = field.estree.append_field_index {
-            let append_field = &struct_def.fields[append_field_index];
-            let append_from_ident = append_field.ident();
-            let wrapper_name = if append_field.type_def(self.schema).is_option() {
-                "AppendTo"
-            } else {
-                "AppendToConcat"
-            };
-            let wrapper_ident = create_safe_ident(wrapper_name);
+            let append_from_ident = struct_def.fields[append_field_index].ident();
             quote! {
-                #wrapper_ident { array: &#self_path.#field_name_ident, after: &#self_path.#append_from_ident  }
+                Concat2(&#self_path.#field_name_ident, &#self_path.#append_from_ident)
             }
         } else if field.estree.json_safe {
             // Wrap value in `JsonSafeString(...)` if field is tagged `#[estree(json_safe)]`

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

@@ -161,6 +161,7 @@ impl TypeDef {
         }
     }
 
+    #[expect(dead_code)]
     pub fn is_option(&self) -> bool {
         matches!(self, Self::Option(_))
     }