Support interfaces that implement other interfaces.

src/schema/ast.rs

@@ -182,6 +182,7 @@ pub struct InterfaceType<'a, T: Text<'a>> {
     pub position: Pos,
     pub description: Option<String>,
     pub name: T::Value,
+    pub implements_interfaces: Vec<T::Value>,
     pub directives: Vec<Directive<'a, T>>,
     pub fields: Vec<Field<'a, T>>,
 }
@@ -194,6 +195,7 @@ impl<'a, T> InterfaceType<'a, T>
             position: Pos::default(),
             description: None,
             name,
+            implements_interfaces: vec![],
             directives: vec![],
             fields: vec![],
         }
@@ -204,6 +206,7 @@ impl<'a, T> InterfaceType<'a, T>
 pub struct InterfaceTypeExtension<'a, T: Text<'a>> {
     pub position: Pos,
     pub name: T::Value,
+    pub implements_interfaces: Vec<T::Value>,
     pub directives: Vec<Directive<'a, T>>,
     pub fields: Vec<Field<'a, T>>,
 }
@@ -215,6 +218,7 @@ where T: Text<'a>
         Self {
             position: Pos::default(),
             name,
+            implements_interfaces: vec![],
             directives: vec![],
             fields: vec![],
         }

src/schema/format.rs

@@ -6,7 +6,7 @@ use crate::common::Text;
 use crate::schema::ast::*;
 
 
-impl<'a, T> Document<'a, T> 
+impl<'a, T> Document<'a, T>
     where T: Text<'a>,
 {
     /// Format a document according to style
@@ -33,7 +33,7 @@ fn description<'a>(description: &Option<String>, f: &mut Formatter) {
 }
 
 
-impl<'a, T> Displayable for Document<'a, T> 
+impl<'a, T> Displayable for Document<'a, T>
     where T: Text<'a>,
 {
     fn display(&self, f: &mut Formatter) {
@@ -43,7 +43,7 @@ impl<'a, T> Displayable for Document<'a, T>
     }
 }
 
-impl<'a, T> Displayable for Definition<'a, T> 
+impl<'a, T> Displayable for Definition<'a, T>
     where T: Text<'a>,
 {
     fn display(&self, f: &mut Formatter) {
@@ -57,7 +57,7 @@ impl<'a, T> Displayable for Definition<'a, T>
     }
 }
 
-impl<'a, T> Displayable for SchemaDefinition<'a, T> 
+impl<'a, T> Displayable for SchemaDefinition<'a, T>
     where T: Text<'a>,
 {
     fn display(&self, f: &mut Formatter) {
@@ -88,7 +88,7 @@ impl<'a, T> Displayable for SchemaDefinition<'a, T>
     }
 }
 
-impl<'a, T> Displayable for TypeDefinition<'a, T> 
+impl<'a, T> Displayable for TypeDefinition<'a, T>
     where T: Text<'a>,
 {
     fn display(&self, f: &mut Formatter) {
@@ -103,7 +103,7 @@ impl<'a, T> Displayable for TypeDefinition<'a, T>
     }
 }
 
-impl<'a, T> Displayable for ScalarType<'a, T> 
+impl<'a, T> Displayable for ScalarType<'a, T>
     where T: Text<'a>,
 {
     fn display(&self, f: &mut Formatter) {
@@ -116,7 +116,7 @@ impl<'a, T> Displayable for ScalarType<'a, T>
     }
 }
 
-impl<'a, T> Displayable for ScalarTypeExtension<'a, T> 
+impl<'a, T> Displayable for ScalarTypeExtension<'a, T>
     where T: Text<'a>,
 {
     fn display(&self, f: &mut Formatter) {
@@ -128,7 +128,7 @@ impl<'a, T> Displayable for ScalarTypeExtension<'a, T>
     }
 }
 
-fn format_fields<'a, T>(fields: &[Field<'a, T>], f: &mut Formatter) 
+fn format_fields<'a, T>(fields: &[Field<'a, T>], f: &mut Formatter)
     where T: Text<'a>,
 {
     if !fields.is_empty() {
@@ -143,7 +143,7 @@ fn format_fields<'a, T>(fields: &[Field<'a, T>], f: &mut Formatter)
     }
 }
 
-impl<'a, T> Displayable for ObjectType<'a, T> 
+impl<'a, T> Displayable for ObjectType<'a, T>
     where T: Text<'a>,
 {
     fn display(&self, f: &mut Formatter) {
@@ -164,7 +164,7 @@ impl<'a, T> Displayable for ObjectType<'a, T>
     }
 }
 
-impl<'a, T> Displayable for ObjectTypeExtension<'a, T> 
+impl<'a, T> Displayable for ObjectTypeExtension<'a, T>
     where T: Text<'a>,
 {
     fn display(&self, f: &mut Formatter) {
@@ -184,7 +184,7 @@ impl<'a, T> Displayable for ObjectTypeExtension<'a, T>
     }
 }
 
-impl<'a, T> Displayable for InputValue<'a, T> 
+impl<'a, T> Displayable for InputValue<'a, T>
     where T: Text<'a>,
 {
     fn display(&self, f: &mut Formatter) {
@@ -203,7 +203,7 @@ impl<'a, T> Displayable for InputValue<'a, T>
     }
 }
 
-fn format_arguments<'a, T>(arguments: &[InputValue<'a, T>], f: &mut Formatter) 
+fn format_arguments<'a, T>(arguments: &[InputValue<'a, T>], f: &mut Formatter)
     where T: Text<'a>,
 {
     if !arguments.is_empty() {
@@ -217,7 +217,7 @@ fn format_arguments<'a, T>(arguments: &[InputValue<'a, T>], f: &mut Formatter)
     }
 }
 
-impl<'a, T> Displayable for Field<'a, T> 
+impl<'a, T> Displayable for Field<'a, T>
     where T: Text<'a>,
 {
     fn display(&self, f: &mut Formatter) {
@@ -232,32 +232,48 @@ impl<'a, T> Displayable for Field<'a, T>
     }
 }
 
-impl<'a, T> Displayable for InterfaceType<'a, T> 
+impl<'a, T> Displayable for InterfaceType<'a, T>
     where T: Text<'a>,
 {
     fn display(&self, f: &mut Formatter) {
         description(&self.description, f);
         f.indent();
         f.write("interface ");
         f.write(self.name.as_ref());
+        if !self.implements_interfaces.is_empty() {
+            f.write(" implements ");
+            f.write(self.implements_interfaces[0].as_ref());
+            for name in &self.implements_interfaces[1..] {
+                f.write(" & ");
+                f.write(name.as_ref());
+            }
+        }
         format_directives(&self.directives, f);
         format_fields(&self.fields, f);
     }
 }
 
-impl<'a, T> Displayable for InterfaceTypeExtension<'a, T> 
+impl<'a, T> Displayable for InterfaceTypeExtension<'a, T>
     where T: Text<'a>,
 {
     fn display(&self, f: &mut Formatter) {
         f.indent();
         f.write("extend interface ");
         f.write(self.name.as_ref());
+        if !self.implements_interfaces.is_empty() {
+            f.write(" implements ");
+            f.write(self.implements_interfaces[0].as_ref());
+            for name in &self.implements_interfaces[1..] {
+                f.write(" & ");
+                f.write(name.as_ref());
+            }
+        }
         format_directives(&self.directives, f);
         format_fields(&self.fields, f);
     }
 }
 
-impl<'a, T> Displayable for UnionType<'a, T> 
+impl<'a, T> Displayable for UnionType<'a, T>
     where T: Text<'a>,
 {
     fn display(&self, f: &mut Formatter) {
@@ -278,7 +294,7 @@ impl<'a, T> Displayable for UnionType<'a, T>
     }
 }
 
-impl<'a, T> Displayable for UnionTypeExtension<'a, T> 
+impl<'a, T> Displayable for UnionTypeExtension<'a, T>
     where T: Text<'a>,
 {
     fn display(&self, f: &mut Formatter) {
@@ -298,7 +314,7 @@ impl<'a, T> Displayable for UnionTypeExtension<'a, T>
     }
 }
 
-impl<'a, T> Displayable for EnumType<'a, T> 
+impl<'a, T> Displayable for EnumType<'a, T>
     where T: Text<'a>,
 {
     fn display(&self, f: &mut Formatter) {
@@ -327,7 +343,7 @@ impl<'a, T> Displayable for EnumType<'a, T>
     }
 }
 
-impl<'a, T> Displayable for EnumTypeExtension<'a, T> 
+impl<'a, T> Displayable for EnumTypeExtension<'a, T>
     where T: Text<'a>,
 {
     fn display(&self, f: &mut Formatter) {
@@ -355,7 +371,7 @@ impl<'a, T> Displayable for EnumTypeExtension<'a, T>
     }
 }
 
-fn format_inputs<'a, T>(fields: &[InputValue<'a, T>], f: &mut Formatter) 
+fn format_inputs<'a, T>(fields: &[InputValue<'a, T>], f: &mut Formatter)
     where T: Text<'a>,
 {
     if !fields.is_empty() {
@@ -372,7 +388,7 @@ fn format_inputs<'a, T>(fields: &[InputValue<'a, T>], f: &mut Formatter)
     }
 }
 
-impl<'a, T> Displayable for InputObjectType<'a, T> 
+impl<'a, T> Displayable for InputObjectType<'a, T>
     where T: Text<'a>,
 {
     fn display(&self, f: &mut Formatter) {
@@ -385,7 +401,7 @@ impl<'a, T> Displayable for InputObjectType<'a, T>
     }
 }
 
-impl<'a, T> Displayable for InputObjectTypeExtension<'a, T> 
+impl<'a, T> Displayable for InputObjectTypeExtension<'a, T>
     where T: Text<'a>,
 {
     fn display(&self, f: &mut Formatter) {
@@ -397,7 +413,7 @@ impl<'a, T> Displayable for InputObjectTypeExtension<'a, T>
     }
 }
 
-impl<'a, T> Displayable for TypeExtension<'a, T> 
+impl<'a, T> Displayable for TypeExtension<'a, T>
     where T: Text<'a>,
 {
     fn display(&self, f: &mut Formatter) {
@@ -412,7 +428,7 @@ impl<'a, T> Displayable for TypeExtension<'a, T>
     }
 }
 
-impl<'a, T> Displayable for DirectiveDefinition<'a, T> 
+impl<'a, T> Displayable for DirectiveDefinition<'a, T>
     where T: Text<'a>,
 {
     fn display(&self, f: &mut Formatter) {
@@ -441,7 +457,7 @@ impl<'a, T> Displayable for DirectiveDefinition<'a, T>
 }
 
 impl_display!(
-    'a 
+    'a
     Document,
     Definition,
     SchemaDefinition,

src/schema/grammar.rs

@@ -241,12 +241,15 @@ pub fn interface_type<'a, T>(input: &mut TokenStream<'a>)
     (
         position(),
         ident("interface").with(name::<'a, T>()),
+        parser(implements_interfaces::<T>),
         parser(directives),
         parser(fields),
     )
-        .map(|(position, name, directives, fields)| {
+        .map(|(position, name, interfaces, directives, fields)| {
             InterfaceType {
-                position, name, directives, fields,
+                position, name,
+                implements_interfaces: interfaces,
+                directives, fields,
                 description: None,  // is filled in described_definition
             }
         })
@@ -260,10 +263,11 @@ pub fn interface_type_extension<'a, T>(input: &mut TokenStream<'a>)
     (
         position(),
         ident("interface").with(name::<'a, T>()),
+        parser(implements_interfaces::<T>),
         parser(directives),
         parser(fields),
     )
-        .flat_map(|(position, name, directives, fields)| {
+        .flat_map(|(position, name, interfaces, directives, fields)| {
             if directives.is_empty() && fields.is_empty() {
                 let mut e = Errors::empty(position);
                 e.add_error(Error::expected_static_message(
@@ -272,7 +276,9 @@ pub fn interface_type_extension<'a, T>(input: &mut TokenStream<'a>)
                 return Err(e);
             }
             Ok(InterfaceTypeExtension {
-                position, name, directives, fields,
+                position, name,
+                implements_interfaces: interfaces,
+                directives, fields,
             })
         })
         .parse_stream(input)

tests/schema_roundtrips.rs

@@ -35,6 +35,7 @@ fn roundtrip2(filename: &str) {
 #[test] fn minimal_type() { roundtrip("minimal_type"); }
 #[test] fn implements() { roundtrip("implements"); }
 #[test] fn implements_amp() { roundtrip2("implements_amp"); }
+#[test] fn implements_interface() { roundtrip("implements_interface"); }
 #[test] fn simple_object() { roundtrip("simple_object"); }
 #[test] fn extend_object() { roundtrip("extend_object"); }
 #[test] fn interface() { roundtrip("interface"); }

tests/schemas/extend_interface.graphql

@@ -1,3 +1,7 @@
 extend interface Bar {
   two(argument: InputType!): Type
 }
+
+extend interface Foo implements IOne & ITwo {
+  three(argument: [InputType!]!): Type
+}

tests/schemas/extend_object.graphql

@@ -1,3 +1,7 @@
 extend type Foo {
   seven(argument: [String]): Type
 }
+
+extend type Bar implements IOne & ITwo {
+  five(argument: [String!]!): Type
+}

tests/schemas/implements_interface.graphql

@@ -0,0 +1,3 @@
+interface IOne implements ITwo
+
+interface IThree implements IFour & IFive