codex: gate empty experimental fields

Co-authored-by: Codex <noreply@openai.com>

codex-rs/app-server-protocol/src/experimental_api.rs

@@ -98,6 +98,13 @@ mod tests {
         inners: HashMap<String, EnumVariantShapes>,
     }
 
+    #[allow(dead_code)]
+    #[derive(ExperimentalApi)]
+    struct ExperimentalFieldShape {
+        #[experimental("field/optionalCollection")]
+        optional_collection: Option<Vec<EnumVariantShapes>>,
+    }
+
     #[test]
     fn derive_supports_all_enum_variant_shapes() {
         assert_eq!(
@@ -169,4 +176,20 @@ mod tests {
             None
         );
     }
+
+    #[test]
+    fn derive_marks_optional_experimental_fields_when_some() {
+        assert_eq!(
+            ExperimentalApiTrait::experimental_reason(&ExperimentalFieldShape {
+                optional_collection: Some(Vec::new()),
+            }),
+            Some("field/optionalCollection")
+        );
+        assert_eq!(
+            ExperimentalApiTrait::experimental_reason(&ExperimentalFieldShape {
+                optional_collection: None,
+            }),
+            None
+        );
+    }
 }

codex-rs/codex-experimental-api-macros/src/lib.rs

@@ -261,11 +261,8 @@ fn presence_expr_for_access(
     access: proc_macro2::TokenStream,
     ty: &Type,
 ) -> proc_macro2::TokenStream {
-    if let Some(inner) = option_inner(ty) {
-        let inner_expr = presence_expr_for_ref(quote!(value), inner);
-        return quote! {
-            #access.as_ref().is_some_and(|value| #inner_expr)
-        };
+    if option_inner(ty).is_some() {
+        return quote! { #access.is_some() };
     }
     if is_vec_like(ty) || is_map_like(ty) {
         return quote! { !#access.is_empty() };