Allow printing interfaces implementing interfaces

Summary:
This seems like an oversight: we can define `interface Foo implements Bar` and the Relay SDLSchema can print this representation out, but the IR syntax cannot.

This diff quickly fixes that oversight.

Reviewed By: alunyov

Differential Revision: D49256355

fbshipit-source-id: 0de06ae10c36105bc81305f63846d08997e1441b

compiler/crates/graphql-syntax/src/node/type_system.rs

@@ -84,16 +84,16 @@ impl fmt::Display for TypeSystemDefinition {
             }) => write_object_helper(f, &name.value, interfaces, fields, directives, true),
             TypeSystemDefinition::InterfaceTypeDefinition(InterfaceTypeDefinition {
                 name,
+                interfaces,
                 fields,
                 directives,
-                ..
-            }) => write_interface_helper(f, &name.value, fields, directives, false),
+            }) => write_interface_helper(f, &name.value, interfaces, fields, directives, false),
             TypeSystemDefinition::InterfaceTypeExtension(InterfaceTypeExtension {
                 name,
-                interfaces: _,
+                interfaces,
                 fields,
                 directives,
-            }) => write_interface_helper(f, &name.value, fields, directives, true),
+            }) => write_interface_helper(f, &name.value, interfaces, fields, directives, true),
             TypeSystemDefinition::UnionTypeDefinition(UnionTypeDefinition {
                 name,
                 directives,
@@ -617,6 +617,7 @@ fn write_object_helper(
 fn write_interface_helper(
     f: &mut fmt::Formatter<'_>,
     name: &StringKey,
+    interfaces: &[Identifier],
     fields: &Option<List<FieldDefinition>>,
     directives: &[ConstantDirective],
     is_extension: bool,
@@ -626,6 +627,10 @@ fn write_interface_helper(
     }
 
     write!(f, "interface {}", name)?;
+    if !interfaces.is_empty() {
+        write!(f, " implements ")?;
+        write_list(f, interfaces, " & ")?;
+    }
     write_directives(f, directives)?;
     if let Some(fields) = fields.as_ref() {
         write_fields(f, &fields.items)?;

compiler/crates/graphql-syntax/tests/print/fixtures/schema.expected

@@ -21,11 +21,19 @@ type Mutation {
   success: boolean
 }
 
-interface XIGHuman @source(schema: "instagram", name: "Human") {
+interface HasName {
   name: String
 }
 
-extend interface XIGHuman {
+interface HasNickname {
+  nickname: String
+}
+
+interface XIGHuman implements Animal @source(schema: "instagram", name: "Human") {
+  name: String
+}
+
+extend interface XIGHuman implements HasNickname {
   nickname: String
 }
 
@@ -104,11 +112,19 @@ type Mutation {
   success: boolean
 }
 
-interface XIGHuman @source(schema: "instagram", name: "Human") {
+interface HasName {
+  name: String
+}
+
+interface HasNickname {
+  nickname: String
+}
+
+interface XIGHuman implements Animal @source(schema: "instagram", name: "Human") {
   name: String
 }
 
-extend interface XIGHuman {
+extend interface XIGHuman implements HasNickname {
   nickname: String
 }
 

compiler/crates/graphql-syntax/tests/print/fixtures/schema.graphql

@@ -20,11 +20,19 @@ type Mutation {
   success: boolean
 }
 
-interface XIGHuman @source(schema: "instagram", name: "Human") {
+interface HasName {
   name: String
 }
 
-extend interface XIGHuman {
+interface HasNickname {
+  nickname: String
+}
+
+interface XIGHuman implements Animal @source(schema: "instagram", name: "Human") {
+  name: String
+}
+
+extend interface XIGHuman implements HasNickname {
   nickname: String
 }