@oneOf input objects (#1062, #1347)

juniper/CHANGELOG.md

@@ -24,7 +24,10 @@ All user visible changes to `juniper` crate will be documented in this file. Thi
 ### Added
 
 - [September 2025] GraphQL spec: ([#1347])
-    - `__Type.isOneOf` field. ([#1348], [graphql/graphql-spec#825])
+    - `@oneOf` input objects: ([#1354], [graphql/graphql-spec#825])
+        - `@oneOf` built-in directive.
+        - `__Type.isOneOf` field. ([#1348])
+        - `schema::meta::InputObjectMeta::is_one_of` field.
     - `SCHEMA`, `OBJECT`, `ARGUMENT_DEFINITION`, `INTERFACE`, `UNION`, `ENUM`, `INPUT_OBJECT` and `INPUT_FIELD_DEFINITION` values to `__DirectiveLocation` enum. ([#1348])
     - Arguments and input object fields deprecation: ([#1348], [#864], [graphql/graphql-spec#525], [graphql/graphql-spec#805])
         - Placing `#[graphql(deprecated)]` and `#[deprecated]` attributes on struct fields in `#[derive(GraphQLInputObject)]` macro.
@@ -54,6 +57,7 @@ All user visible changes to `juniper` crate will be documented in this file. Thi
 [#1348]: /../../pull/1348
 [#1349]: /../../pull/1349
 [#1353]: /../../pull/1353
+[#1354]: /../../pull/1354
 [graphql/graphql-spec#525]: https://github.com/graphql/graphql-spec/pull/525
 [graphql/graphql-spec#687]: https://github.com/graphql/graphql-spec/issues/687
 [graphql/graphql-spec#805]: https://github.com/graphql/graphql-spec/pull/805

juniper/src/schema/meta.rs

@@ -348,6 +348,8 @@ pub struct InputObjectMeta<S> {
     pub description: Option<ArcStr>,
     #[doc(hidden)]
     pub input_fields: Vec<Argument<S>>,
+    #[doc(hidden)]
+    pub is_one_of: bool,
     #[debug(ignore)]
     pub(crate) try_parse_fn: InputValueParseFn<S>,
 }
@@ -364,6 +366,7 @@ impl<S> InputObjectMeta<S> {
             name: name.into(),
             description: None,
             input_fields: input_fields.to_vec(),
+            is_one_of: false,
             try_parse_fn: try_parse_fn::<S, T>,
         }
     }
@@ -377,6 +380,15 @@ impl<S> InputObjectMeta<S> {
         self
     }
 
+    /// Marks this [`InputObjectMeta`] type as [`@oneOf`].
+    ///
+    /// [`@oneOf`]: https://spec.graphql.org/September2025#sec--oneOf
+    #[must_use]
+    pub fn one_of(mut self) -> Self {
+        self.is_one_of = true;
+        self
+    }
+
     /// Wraps this [`InputObjectMeta`] type into a generic [`MetaType`].
     pub fn into_meta(self) -> MetaType<S> {
         MetaType::InputObject(self)

juniper/src/schema/model.rs

@@ -250,14 +250,16 @@ impl<S> SchemaType<S> {
 
         registry.get_type::<SchemaType<S>>(&());
 
+        let deprecated_directive = DirectiveType::new_deprecated(&mut registry);
         let include_directive = DirectiveType::new_include(&mut registry);
+        let one_of_directive = DirectiveType::new_one_of();
         let skip_directive = DirectiveType::new_skip(&mut registry);
-        let deprecated_directive = DirectiveType::new_deprecated(&mut registry);
         let specified_by_directive = DirectiveType::new_specified_by(&mut registry);
         directives.insert(include_directive.name.clone(), include_directive);
         directives.insert(skip_directive.name.clone(), skip_directive);
         directives.insert(deprecated_directive.name.clone(), deprecated_directive);
         directives.insert(specified_by_directive.name.clone(), specified_by_directive);
+        directives.insert(one_of_directive.name.clone(), one_of_directive);
 
         let mut meta_fields = vec![
             registry.field::<SchemaType<S>>(arcstr::literal!("__schema"), &()),
@@ -585,28 +587,33 @@ impl<S> DirectiveType<S> {
         }
     }
 
-    fn new_include(registry: &mut Registry<S>) -> Self
+    fn new_deprecated(registry: &mut Registry<S>) -> Self
     where
         S: ScalarValue,
     {
         Self::new(
-            arcstr::literal!("include"),
+            arcstr::literal!("deprecated"),
             &[
-                DirectiveLocation::Field,
-                DirectiveLocation::FragmentSpread,
-                DirectiveLocation::InlineFragment,
+                DirectiveLocation::FieldDefinition,
+                DirectiveLocation::ArgumentDefinition,
+                DirectiveLocation::InputFieldDefinition,
+                DirectiveLocation::EnumValue,
             ],
-            &[registry.arg::<bool>(arcstr::literal!("if"), &())],
+            &[registry.arg_with_default::<String>(
+                arcstr::literal!("reason"),
+                &"No longer supported".into(),
+                &(),
+            )],
             false,
         )
     }
 
-    fn new_skip(registry: &mut Registry<S>) -> Self
+    fn new_include(registry: &mut Registry<S>) -> Self
     where
         S: ScalarValue,
     {
         Self::new(
-            arcstr::literal!("skip"),
+            arcstr::literal!("include"),
             &[
                 DirectiveLocation::Field,
                 DirectiveLocation::FragmentSpread,
@@ -617,23 +624,30 @@ impl<S> DirectiveType<S> {
         )
     }
 
-    fn new_deprecated(registry: &mut Registry<S>) -> Self
+    fn new_one_of() -> Self
     where
         S: ScalarValue,
     {
         Self::new(
-            arcstr::literal!("deprecated"),
+            arcstr::literal!("oneOf"),
+            &[DirectiveLocation::InputObject],
+            &[],
+            false,
+        )
+    }
+
+    fn new_skip(registry: &mut Registry<S>) -> Self
+    where
+        S: ScalarValue,
+    {
+        Self::new(
+            arcstr::literal!("skip"),
             &[
-                DirectiveLocation::FieldDefinition,
-                DirectiveLocation::ArgumentDefinition,
-                DirectiveLocation::InputFieldDefinition,
-                DirectiveLocation::EnumValue,
+                DirectiveLocation::Field,
+                DirectiveLocation::FragmentSpread,
+                DirectiveLocation::InlineFragment,
             ],
-            &[registry.arg_with_default::<String>(
-                arcstr::literal!("reason"),
-                &"No longer supported".into(),
-                &(),
-            )],
+            &[registry.arg::<bool>(arcstr::literal!("if"), &())],
             false,
         )
     }

juniper/src/schema/schema.rs

@@ -375,8 +375,7 @@ impl<'a, S: ScalarValue + 'a> TypeType<'a, S> {
     fn is_one_of(&self) -> Option<bool> {
         match self {
             Self::Concrete(t) => match t {
-                // TODO: Implement once `@oneOf` is implemented for input objects.
-                MetaType::InputObject(InputObjectMeta { .. }) => Some(false),
+                MetaType::InputObject(InputObjectMeta { is_one_of, .. }) => Some(*is_one_of),
                 MetaType::Enum(..)
                 | MetaType::Interface(..)
                 | MetaType::List(..)

juniper/src/schema/translate/graphql_parser.rs

@@ -83,7 +83,9 @@ impl GraphQLParserTranslator {
             default_value: default_value
                 .as_ref()
                 .map(|x| GraphQLParserTranslator::translate_value(x)),
-            directives: generate_directives(deprecation_status),
+            directives: deprecation_directive(deprecation_status)
+                .map(|d| vec![d])
+                .unwrap_or_default(),
         }
     }
 
@@ -159,7 +161,7 @@ impl GraphQLParserTranslator {
                 name: name.as_str().into(),
                 directives: specified_by_url
                     .as_deref()
-                    .map(|url| vec![specified_by_url_to_directive(url)])
+                    .map(|url| vec![specified_by_url_directive(url)])
                     .unwrap_or_default(),
             }),
             meta::MetaType::Enum(meta::EnumMeta {
@@ -209,12 +211,15 @@ impl GraphQLParserTranslator {
                 name,
                 description,
                 input_fields,
+                is_one_of,
                 try_parse_fn: _,
             }) => schema::TypeDefinition::InputObject(schema::InputObjectType {
                 position: Pos::default(),
                 description: description.as_deref().map(Into::into),
                 name: name.as_str().into(),
-                directives: vec![],
+                directives: is_one_of
+                    .then(|| vec![one_of_directive()])
+                    .unwrap_or_default(),
                 fields: input_fields
                     .iter()
                     .filter(|x| !x.is_builtin())
@@ -255,7 +260,9 @@ impl GraphQLParserTranslator {
             position: Pos::default(),
             name: name.as_str().into(),
             description: description.as_deref().map(Into::into),
-            directives: generate_directives(deprecation_status),
+            directives: deprecation_directive(deprecation_status)
+                .map(|d| vec![d])
+                .unwrap_or_default(),
         }
     }
 
@@ -275,7 +282,9 @@ impl GraphQLParserTranslator {
             position: Pos::default(),
             name: name.as_str().into(),
             description: description.as_deref().map(Into::into),
-            directives: generate_directives(deprecation_status),
+            directives: deprecation_directive(deprecation_status)
+                .map(|d| vec![d])
+                .unwrap_or_default(),
             field_type: GraphQLParserTranslator::translate_type(field_type),
             arguments: arguments
                 .as_ref()
@@ -290,7 +299,11 @@ impl GraphQLParserTranslator {
     }
 }
 
-fn deprecation_to_directive<'a, T>(
+/// Forms a [`@deprecated(reason:)`] [`schema::Directive`] out of the provided
+/// [`meta::DeprecationStatus`].
+///
+/// [`@deprecated(reason:)`]: https://spec.graphql.org/September2025#sec--deprecated
+fn deprecation_directive<'a, T>(
     status: &meta::DeprecationStatus,
 ) -> Option<schema::Directive<'a, T>>
 where
@@ -309,28 +322,32 @@ where
     }
 }
 
-/// Returns the `@specifiedBy(url:)` [`schema::Directive`] for the provided `url`.
-fn specified_by_url_to_directive<'a, T>(url: &str) -> schema::Directive<'a, T>
+/// Forms a [`@oneOf`] [`schema::Directive`].
+///
+/// [`@oneOf`]: https://spec.graphql.org/September2025#sec--oneOf
+fn one_of_directive<'a, T>() -> schema::Directive<'a, T>
 where
     T: schema::Text<'a>,
 {
     schema::Directive {
         position: Pos::default(),
-        name: "specifiedBy".into(),
-        arguments: vec![("url".into(), schema::Value::String(url.into()))],
+        name: "oneOf".into(),
+        arguments: vec![],
     }
 }
 
-// Right now the only directive supported is `@deprecated`.
-// `@skip` and `@include` are dealt with elsewhere.
-// https://spec.graphql.org/October2021#sec-Type-System.Directives.Built-in-Directives
-fn generate_directives<'a, T>(status: &meta::DeprecationStatus) -> Vec<schema::Directive<'a, T>>
+/// Forms a `@specifiedBy(url:)` [`schema::Directive`] out of the provided `url`.
+///
+/// [`@specifiedBy(url:)`]: https://spec.graphql.org/September2025#sec--specifiedBy
+fn specified_by_url_directive<'a, T>(url: &str) -> schema::Directive<'a, T>
 where
     T: schema::Text<'a>,
 {
-    deprecation_to_directive(status)
-        .map(|d| vec![d])
-        .unwrap_or_default()
+    schema::Directive {
+        position: Pos::default(),
+        name: "specifiedBy".into(),
+        arguments: vec![("url".into(), schema::Value::String(url.into()))],
+    }
 }
 
 /// Sorts the provided [`schema::Document`] in the "type-then-name" manner.