Ignore serde attributes specta does not model (fixes remote = "Self")

specta-macros/src/type/serde.rs

@@ -1,6 +1,6 @@
-use proc_macro2::TokenStream;
+use proc_macro2::{TokenStream, TokenTree};
 use quote::quote;
-use syn::{Attribute, LitStr, Meta, Result, Type, meta::ParseNestedMeta};
+use syn::{Attribute, Expr, LitStr, Meta, Result, Token, Type, meta::ParseNestedMeta, token};
 
 use super::AttributeScope;
 
@@ -210,11 +210,26 @@ fn parse_container_meta(target: &mut ContainerAttrs, meta: ParseNestedMeta<'_>)
         target.variant_identifier = true;
     } else if meta.path.is_ident("field_identifier") {
         target.field_identifier = true;
+    } else {
+        skip_unknown_meta(&meta)?;
     }
 
     Ok(())
 }
 
+/// serde owns and validates its attribute namespace, so keys specta does not model (e.g.
+/// container `remote`/`bound`/`expecting`, variant `bound`, field `getter`) are ignored - but
+/// their value must still be consumed, or `parse_nested_meta` fails the whole derive with
+/// "expected `,`" on the leftover tokens.
+fn skip_unknown_meta(meta: &ParseNestedMeta<'_>) -> Result<()> {
+    if meta.input.peek(Token![=]) {
+        meta.value()?.parse::<Expr>()?;
+    } else if meta.input.peek(token::Paren) {
+        meta.input.parse::<TokenTree>()?;
+    }
+    Ok(())
+}
+
 fn parse_variant_meta(target: &mut VariantAttrs, meta: ParseNestedMeta<'_>) -> Result<()> {
     if meta.path.is_ident("rename") {
         parse_rename(
@@ -250,6 +265,8 @@ fn parse_variant_meta(target: &mut VariantAttrs, meta: ParseNestedMeta<'_>) -> R
         target.other = true;
     } else if meta.path.is_ident("untagged") {
         target.untagged = true;
+    } else {
+        skip_unknown_meta(&meta)?;
     }
 
     Ok(())
@@ -287,6 +304,8 @@ fn parse_field_meta(target: &mut FieldAttrs, meta: ParseNestedMeta<'_>) -> Resul
     } else if meta.path.is_ident("with") {
         target.has_with = true;
         parse_string_assignment(&meta)?;
+    } else {
+        skip_unknown_meta(&meta)?;
     }
 
     Ok(())

tests/tests/mod.rs

@@ -23,6 +23,7 @@ mod semantic;
 mod serde_conversions;
 mod serde_identifiers;
 mod serde_other;
+mod serde_unknown_attrs;
 mod swift;
 mod types;
 mod typescript;

tests/tests/serde_unknown_attrs.rs

@@ -0,0 +1,106 @@
+//! specta models only a subset of serde's attribute namespace, and serde validates that
+//! namespace itself - so attributes specta does not model must be ignored, not rejected.
+//! Ignoring a name-value or list attribute still requires consuming its tokens: returning
+//! from the `parse_nested_meta` callback without doing so makes syn fail the whole derive
+//! with "expected `,`".
+//!
+//! The trigger case was `#[serde(remote = "Self")]`, which makes the serde derives emit
+//! inherent `serialize`/`deserialize` functions so the trait impls can be written by hand
+//! (e.g. to migrate a document before parsing it). Container `bound`/`expecting`, variant
+//! `bound`, and field `getter` hit the same paths in each attribute scope.
+
+use serde::{Deserialize, Serialize};
+use specta::{Type, Types};
+use specta_typescript::Typescript;
+
+#[derive(Type, Serialize, Deserialize)]
+#[specta(collect = false)]
+#[serde(remote = "Self")]
+struct RemoteSelf {
+    value: i32,
+    #[serde(default)]
+    label: Option<String>,
+}
+
+#[derive(Type, Serialize)]
+#[specta(collect = false)]
+#[serde(bound = "T: Serialize + Clone")]
+struct ContainerBound<T> {
+    inner: T,
+}
+
+#[derive(Type, Deserialize)]
+#[specta(collect = false)]
+#[serde(expecting = "a remote self")]
+struct ContainerExpecting {
+    id: u32,
+}
+
+#[derive(Type, Serialize)]
+#[specta(collect = false)]
+enum VariantBound<T> {
+    #[serde(bound = "T: Serialize")]
+    Value(T),
+    Empty,
+}
+
+struct Seconds(i32);
+
+impl Seconds {
+    fn value(&self) -> i32 {
+        self.0
+    }
+}
+
+// The remote-definition pattern: serde reads the real type's fields through getters.
+#[derive(Type, Serialize)]
+#[specta(collect = false)]
+#[serde(remote = "Seconds")]
+struct SecondsDef {
+    #[serde(getter = "Seconds::value")]
+    value: i32,
+}
+
+#[test]
+fn unknown_serde_attributes_are_ignored() {
+    let rendered = Typescript::default()
+        .export(
+            &Types::default().register::<RemoteSelf>(),
+            specta_serde::Format,
+        )
+        .expect("remote = \"Self\" must not affect the exported type");
+    assert!(rendered.contains("value: number"), "got: {rendered}");
+    assert!(rendered.contains("label"), "got: {rendered}");
+
+    let rendered = Typescript::default()
+        .export(
+            &Types::default().register::<ContainerBound<String>>(),
+            specta_serde::Format,
+        )
+        .expect("container bound must not affect the exported type");
+    assert!(rendered.contains("inner"), "got: {rendered}");
+
+    let rendered = Typescript::default()
+        .export(
+            &Types::default().register::<ContainerExpecting>(),
+            specta_serde::Format,
+        )
+        .expect("container expecting must not affect the exported type");
+    assert!(rendered.contains("id: number"), "got: {rendered}");
+
+    let rendered = Typescript::default()
+        .export(
+            &Types::default().register::<VariantBound<String>>(),
+            specta_serde::Format,
+        )
+        .expect("variant bound must not affect the exported type");
+    assert!(rendered.contains("Value"), "got: {rendered}");
+
+    let rendered = Typescript::default()
+        .export(
+            &Types::default().register::<SecondsDef>(),
+            specta_serde::Format,
+        )
+        .expect("field getter must not affect the exported type");
+    assert!(rendered.contains("value: number"), "got: {rendered}");
+}