RFC: SchemaExtension

This adds support for graphql/graphql-spec#428 spec proposal.

So far this just adds language support and updates validation rules to be aware of this new ast node. I'll follow up with support in `extendSchema()` and tests.

src/index.js

@@ -245,7 +245,9 @@ export type {
   EnumTypeDefinitionNode,
   EnumValueDefinitionNode,
   InputObjectTypeDefinitionNode,
+  TypeSystemExtensionNode,
   TypeExtensionNode,
+  SchemaExtensionNode,
   ObjectTypeExtensionNode,
   DirectiveDefinitionNode,
   KindEnum,

src/language/__tests__/schema-kitchen-sink.graphql

@@ -123,3 +123,9 @@ directive @include2(if: Boolean!) on
   | FIELD
   | FRAGMENT_SPREAD
   | INLINE_FRAGMENT
+
+extend schema @onSchema
+
+extend schema @onSchema {
+  subscription: SubscriptionType
+}

src/language/__tests__/schema-printer-test.js

@@ -161,6 +161,12 @@ describe('Printer: SDL document', () => {
       directive @include(if: Boolean!) on FIELD | FRAGMENT_SPREAD | INLINE_FRAGMENT
 
       directive @include2(if: Boolean!) on FIELD | FRAGMENT_SPREAD | INLINE_FRAGMENT
+
+      extend schema @onSchema
+
+      extend schema @onSchema {
+        subscription: SubscriptionType
+      }
     `);
   });
 });

src/language/ast.js

@@ -124,6 +124,7 @@ export type ASTNode =
   | EnumTypeDefinitionNode
   | EnumValueDefinitionNode
   | InputObjectTypeDefinitionNode
+  | SchemaExtensionNode
   | ScalarTypeExtensionNode
   | ObjectTypeExtensionNode
   | InterfaceTypeExtensionNode
@@ -171,6 +172,7 @@ export type ASTKindToNode = {
   EnumTypeDefinition: EnumTypeDefinitionNode,
   EnumValueDefinition: EnumValueDefinitionNode,
   InputObjectTypeDefinition: InputObjectTypeDefinitionNode,
+  SchemaExtension: SchemaExtensionNode,
   ScalarTypeExtension: ScalarTypeExtensionNode,
   ObjectTypeExtension: ObjectTypeExtensionNode,
   InterfaceTypeExtension: InterfaceTypeExtensionNode,
@@ -388,7 +390,7 @@ export type NonNullTypeNode = {
 export type TypeSystemDefinitionNode =
   | SchemaDefinitionNode
   | TypeDefinitionNode
-  | TypeExtensionNode
+  | TypeSystemExtensionNode
   | DirectiveDefinitionNode;
 
 export type SchemaDefinitionNode = {
@@ -499,6 +501,8 @@ export type InputObjectTypeDefinitionNode = {
 
 // Type Extensions
 
+export type TypeSystemExtensionNode = SchemaExtensionNode | TypeExtensionNode;
+
 export type TypeExtensionNode =
   | ScalarTypeExtensionNode
   | ObjectTypeExtensionNode
@@ -507,6 +511,13 @@ export type TypeExtensionNode =
   | EnumTypeExtensionNode
   | InputObjectTypeExtensionNode;
 
+export type SchemaExtensionNode = {
+  +kind: 'SchemaExtension',
+  +loc?: Location,
+  +directives: $ReadOnlyArray<DirectiveNode>,
+  +operationTypes: $ReadOnlyArray<OperationTypeDefinitionNode>,
+};
+
 export type ScalarTypeExtensionNode = {
   +kind: 'ScalarTypeExtension',
   +loc?: Location,

src/language/index.js

@@ -76,7 +76,9 @@ export type {
   EnumTypeDefinitionNode,
   EnumValueDefinitionNode,
   InputObjectTypeDefinitionNode,
+  TypeSystemExtensionNode,
   TypeExtensionNode,
+  SchemaExtensionNode,
   ObjectTypeExtensionNode,
   DirectiveDefinitionNode,
 } from './ast';

src/language/kinds.js

@@ -62,7 +62,8 @@ export const Kind = Object.freeze({
   ENUM_VALUE_DEFINITION: 'EnumValueDefinition',
   INPUT_OBJECT_TYPE_DEFINITION: 'InputObjectTypeDefinition',
 
-  // Type Extensions
+  // Type System Extensions
+  SCHEMA_EXTENSION: 'SchemaExtension',
   SCALAR_TYPE_EXTENSION: 'ScalarTypeExtension',
   OBJECT_TYPE_EXTENSION: 'ObjectTypeExtension',
   INTERFACE_TYPE_EXTENSION: 'InterfaceTypeExtension',

src/language/parser.js

@@ -52,7 +52,8 @@ import type {
   EnumTypeDefinitionNode,
   EnumValueDefinitionNode,
   InputObjectTypeDefinitionNode,
-  TypeExtensionNode,
+  TypeSystemExtensionNode,
+  SchemaExtensionNode,
   ScalarTypeExtensionNode,
   ObjectTypeExtensionNode,
   InterfaceTypeExtensionNode,
@@ -751,9 +752,9 @@ export function parseNamedType(lexer: Lexer<*>): NamedTypeNode {
 
 /**
  * TypeSystemDefinition :
+ *   - TypeSystemExtension
  *   - SchemaDefinition
  *   - TypeDefinition
- *   - TypeExtension
  *   - DirectiveDefinition
  *
  * TypeDefinition :
@@ -785,7 +786,7 @@ function parseTypeSystemDefinition(lexer: Lexer<*>): TypeSystemDefinitionNode {
       case 'input':
         return parseInputObjectTypeDefinition(lexer);
       case 'extend':
-        return parseTypeExtension(lexer);
+        return parseTypeSystemExtension(lexer);
       case 'directive':
         return parseDirectiveDefinition(lexer);
     }
@@ -1141,6 +1142,10 @@ function parseInputFieldsDefinition(
 }
 
 /**
+ * TypeSystemExtension :
+ *   - SchemaExtension
+ *   - TypeExtension
+ *
  * TypeExtension :
  *   - ScalarTypeExtension
  *   - ObjectTypeExtension
@@ -1149,11 +1154,13 @@ function parseInputFieldsDefinition(
  *   - EnumTypeExtension
  *   - InputObjectTypeDefinition
  */
-function parseTypeExtension(lexer: Lexer<*>): TypeExtensionNode {
+function parseTypeSystemExtension(lexer: Lexer<*>): TypeSystemExtensionNode {
   const keywordToken = lexer.lookahead();
 
   if (keywordToken.kind === TokenKind.NAME) {
     switch (keywordToken.value) {
+      case 'schema':
+        return parseSchemaExtension(lexer);
       case 'scalar':
         return parseScalarTypeExtension(lexer);
       case 'type':
@@ -1172,6 +1179,35 @@ function parseTypeExtension(lexer: Lexer<*>): TypeExtensionNode {
   throw unexpected(lexer, keywordToken);
 }
 
+/**
+ * SchemaExtension :
+ *  - extend schema Directives[Const]? { OperationTypeDefinition+ }
+ *  - extend schema Directives[Const]
+ */
+function parseSchemaExtension(lexer: Lexer<*>): SchemaExtensionNode {
+  const start = lexer.token;
+  expectKeyword(lexer, 'extend');
+  expectKeyword(lexer, 'schema');
+  const directives = parseDirectives(lexer, true);
+  const operationTypes = peek(lexer, TokenKind.BRACE_L)
+    ? many(
+        lexer,
+        TokenKind.BRACE_L,
+        parseOperationTypeDefinition,
+        TokenKind.BRACE_R,
+      )
+    : [];
+  if (directives.length === 0 && operationTypes.length === 0) {
+    throw unexpected(lexer);
+  }
+  return {
+    kind: Kind.SCHEMA_EXTENSION,
+    directives,
+    operationTypes,
+    loc: loc(lexer, start),
+  };
+}
+
 /**
  * ScalarTypeExtension :
  *   - extend scalar Name Directives[Const]

src/language/printer.js

@@ -175,6 +175,9 @@ const printDocASTReducer = {
     join(['input', name, join(directives, ' '), block(fields)], ' '),
   ),
 
+  SchemaExtension: ({ directives, operationTypes }) =>
+    join(['extend schema', join(directives, ' '), block(operationTypes)], ' '),
+
   ScalarTypeExtension: ({ name, directives }) =>
     join(['extend scalar', name, join(directives, ' ')], ' '),
 

src/language/visitor.js

@@ -99,6 +99,7 @@ export const QueryDocumentKeys = {
   NonNullType: ['type'],
 
   SchemaDefinition: ['directives', 'operationTypes'],
+  SchemaExtension: ['directives', 'operationTypes'],
   OperationTypeDefinition: ['type'],
 
   ScalarTypeDefinition: ['description', 'name', 'directives'],

src/validation/rules/ExecutableDefinitions.js

@@ -33,7 +33,8 @@ export function ExecutableDefinitions(context: ValidationContext): ASTVisitor {
           context.reportError(
             new GraphQLError(
               nonExecutableDefinitionMessage(
-                definition.kind === Kind.SCHEMA_DEFINITION
+                definition.kind === Kind.SCHEMA_DEFINITION ||
+                definition.kind === Kind.SCHEMA_EXTENSION
                   ? 'schema'
                   : definition.name.value,
               ),

src/validation/rules/KnownDirectives.js

@@ -83,6 +83,7 @@ function getDirectiveLocationForASTPath(ancestors) {
       case Kind.FRAGMENT_DEFINITION:
         return DirectiveLocation.FRAGMENT_DEFINITION;
       case Kind.SCHEMA_DEFINITION:
+      case Kind.SCHEMA_EXTENSION:
         return DirectiveLocation.SCHEMA;
       case Kind.SCALAR_TYPE_DEFINITION:
       case Kind.SCALAR_TYPE_EXTENSION: