Add support for directives on directive definitions (#4521)

Allow directives on directive definitions, based on [this spec PR](graphql/graphql-spec#1206) which introduces this syntax:

```graphql
directive @onDirective on DIRECTIVE_DEFINITION

directive @foo @onDirective on OBJECT

directive @baz @deprecated(reason: "...") on OBJECT

extend directive @quux @deprecated(reason: "...")
```

Co-authored-by: Martin Bonnin <martin@mbonnin.net>
Co-authored-by: Jerel Miller <jerelmiller@gmail.com>
Co-authored-by: Yaacov Rydzinski <yaacovCR@gmail.com>

Author: 4 people

src/index.ts

@@ -312,6 +312,7 @@ export type {
   UnionTypeExtensionNode,
   EnumTypeExtensionNode,
   InputObjectTypeExtensionNode,
+  DirectiveExtensionNode,
   // Schema Coordinates
   SchemaCoordinateNode,
   TypeCoordinateNode,

src/language/__tests__/predicates-test.ts

@@ -39,6 +39,7 @@ describe('AST node predicates', () => {
       'InputObjectTypeDefinition',
       'DirectiveDefinition',
       'SchemaExtension',
+      'DirectiveExtension',
       'ScalarTypeExtension',
       'ObjectTypeExtension',
       'InterfaceTypeExtension',
@@ -123,6 +124,7 @@ describe('AST node predicates', () => {
   it('isTypeSystemExtensionNode', () => {
     expect(filterNodes(isTypeSystemExtensionNode)).to.deep.equal([
       'SchemaExtension',
+      'DirectiveExtension',
       'ScalarTypeExtension',
       'ObjectTypeExtension',
       'InterfaceTypeExtension',

src/language/__tests__/printer-test.ts

@@ -122,6 +122,21 @@ describe('Printer: Query document', () => {
     `);
   });
 
+  it('Experimental: prints directives on directives', () => {
+    const queryASTWithVariableDirective = parse(
+      `
+      directive @foo @bar on FIELD_DEFINITION
+      extend directive @foo @baz
+      `,
+      { experimentalDirectivesOnDirectiveDefinitions: true },
+    );
+    expect(print(queryASTWithVariableDirective)).to.equal(dedent`
+      directive @foo @bar on FIELD_DEFINITION
+      
+      extend directive @foo @baz
+    `);
+  });
+
   it('Legacy: correctly prints fragment defined variables', () => {
     const fragmentWithVariable = parse(
       `

src/language/__tests__/schema-parser-test.ts

@@ -1029,6 +1029,7 @@ input Hello {
         {
           kind: 'DirectiveDefinition',
           description: undefined,
+          directives: [],
           name: {
             kind: 'Name',
             value: 'foo',
@@ -1065,6 +1066,7 @@ input Hello {
         {
           kind: 'DirectiveDefinition',
           description: undefined,
+          directives: [],
           name: {
             kind: 'Name',
             value: 'foo',

src/language/ast.ts

@@ -180,6 +180,7 @@ export type ASTNode =
   | UnionTypeExtensionNode
   | EnumTypeExtensionNode
   | InputObjectTypeExtensionNode
+  | DirectiveExtensionNode
   | TypeCoordinateNode
   | MemberCoordinateNode
   | ArgumentCoordinateNode
@@ -280,10 +281,18 @@ export const QueryDocumentKeys: {
   EnumValueDefinition: ['description', 'name', 'directives'],
   InputObjectTypeDefinition: ['description', 'name', 'directives', 'fields'],
 
-  DirectiveDefinition: ['description', 'name', 'arguments', 'locations'],
+  DirectiveDefinition: [
+    'description',
+    'name',
+    'arguments',
+    'directives',
+    'locations',
+  ],
 
   SchemaExtension: ['directives', 'operationTypes'],
 
+  DirectiveExtension: ['name', 'directives'],
+
   ScalarTypeExtension: ['name', 'directives'],
   ObjectTypeExtension: ['name', 'interfaces', 'directives', 'fields'],
   InterfaceTypeExtension: ['name', 'interfaces', 'directives', 'fields'],
@@ -686,13 +695,17 @@ export interface DirectiveDefinitionNode {
   readonly description?: StringValueNode;
   readonly name: NameNode;
   readonly arguments?: ReadonlyArray<InputValueDefinitionNode>;
+  readonly directives?: ReadonlyArray<ConstDirectiveNode>;
   readonly repeatable: boolean;
   readonly locations: ReadonlyArray<NameNode>;
 }
 
 /** Type System Extensions */
 
-export type TypeSystemExtensionNode = SchemaExtensionNode | TypeExtensionNode;
+export type TypeSystemExtensionNode =
+  | SchemaExtensionNode
+  | TypeExtensionNode
+  | DirectiveExtensionNode;
 
 export interface SchemaExtensionNode {
   readonly kind: Kind.SCHEMA_EXTENSION;
@@ -760,6 +773,13 @@ export interface InputObjectTypeExtensionNode {
   readonly fields?: ReadonlyArray<InputValueDefinitionNode>;
 }
 
+export interface DirectiveExtensionNode {
+  readonly kind: Kind.DIRECTIVE_EXTENSION;
+  readonly loc?: Location;
+  readonly name: NameNode;
+  readonly directives?: ReadonlyArray<ConstDirectiveNode>;
+}
+
 /** Schema Coordinates */
 
 export type SchemaCoordinateNode =

src/language/directiveLocation.ts

@@ -23,6 +23,7 @@ enum DirectiveLocation {
   ENUM_VALUE = 'ENUM_VALUE',
   INPUT_OBJECT = 'INPUT_OBJECT',
   INPUT_FIELD_DEFINITION = 'INPUT_FIELD_DEFINITION',
+  DIRECTIVE_DEFINITION = 'DIRECTIVE_DEFINITION',
 }
 export { DirectiveLocation };
 

src/language/index.ts

@@ -96,6 +96,7 @@ export type {
   UnionTypeExtensionNode,
   EnumTypeExtensionNode,
   InputObjectTypeExtensionNode,
+  DirectiveExtensionNode,
   // Schema Coordinates
   SchemaCoordinateNode,
   TypeCoordinateNode,

src/language/kinds.ts

@@ -58,6 +58,7 @@ enum Kind {
 
   /** Type System Extensions */
   SCHEMA_EXTENSION = 'SchemaExtension',
+  DIRECTIVE_EXTENSION = 'DirectiveExtension',
 
   /** Type Extensions */
   SCALAR_TYPE_EXTENSION = 'ScalarTypeExtension',

src/language/parser.ts

@@ -17,6 +17,7 @@ import type {
   DirectiveArgumentCoordinateNode,
   DirectiveCoordinateNode,
   DirectiveDefinitionNode,
+  DirectiveExtensionNode,
   DirectiveNode,
   DocumentNode,
   EnumTypeDefinitionNode,
@@ -112,6 +113,18 @@ export interface ParseOptions {
    */
   allowLegacyFragmentVariables?: boolean;
 
+  /**
+   * EXPERIMENTAL:
+   *
+   * If enabled, the parser will parse directives on directive definitions.
+   * This syntax is not part of the GraphQL specification and may change.
+   *
+   * ```graphql
+   * directive @foo @bar on FIELD
+   * ```
+   */
+  experimentalDirectivesOnDirectiveDefinitions?: boolean;
+
   /**
    * You may override the Lexer class used to lex the source; this is used by
    * schema coordinates to introduce a lexer with a restricted syntax.
@@ -1184,6 +1197,7 @@ export class Parser {
    *   - UnionTypeExtension
    *   - EnumTypeExtension
    *   - InputObjectTypeDefinition
+   *   - DirectiveDefinitionExtension
    */
   parseTypeSystemExtension(): TypeSystemExtensionNode {
     const keywordToken = this._lexer.lookahead();
@@ -1204,6 +1218,11 @@ export class Parser {
           return this.parseEnumTypeExtension();
         case 'input':
           return this.parseInputObjectTypeExtension();
+        case 'directive':
+          if (this._options.experimentalDirectivesOnDirectiveDefinitions) {
+            return this.parseDirectiveDefinitionExtension();
+          }
+          break;
       }
     }
 
@@ -1386,6 +1405,23 @@ export class Parser {
     });
   }
 
+  parseDirectiveDefinitionExtension(): DirectiveExtensionNode {
+    const start = this._lexer.token;
+    this.expectKeyword('extend');
+    this.expectKeyword('directive');
+    this.expectToken(TokenKind.AT);
+    const name = this.parseName();
+    const directives = this.parseConstDirectives();
+    if (directives.length === 0) {
+      throw this.unexpected();
+    }
+    return this.node<DirectiveExtensionNode>(start, {
+      kind: Kind.DIRECTIVE_EXTENSION,
+      name,
+      directives,
+    });
+  }
+
   /**
    * ```
    * DirectiveDefinition :
@@ -1399,6 +1435,10 @@ export class Parser {
     this.expectToken(TokenKind.AT);
     const name = this.parseName();
     const args = this.parseArgumentDefs();
+    const directives = this._options
+      .experimentalDirectivesOnDirectiveDefinitions
+      ? this.parseConstDirectives()
+      : [];
     const repeatable = this.expectOptionalKeyword('repeatable');
     this.expectKeyword('on');
     const locations = this.parseDirectiveLocations();
@@ -1407,6 +1447,7 @@ export class Parser {
       description,
       name,
       arguments: args,
+      directives,
       repeatable,
       locations,
     });
@@ -1447,6 +1488,7 @@ export class Parser {
    *   `ENUM_VALUE`
    *   `INPUT_OBJECT`
    *   `INPUT_FIELD_DEFINITION`
+   *   `DIRECTIVE_DEFINITION`
    */
   parseDirectiveLocation(): NameNode {
     const start = this._lexer.token;

src/language/predicates.ts

@@ -98,7 +98,11 @@ export function isTypeDefinitionNode(
 export function isTypeSystemExtensionNode(
   node: ASTNode,
 ): node is TypeSystemExtensionNode {
-  return node.kind === Kind.SCHEMA_EXTENSION || isTypeExtensionNode(node);
+  return (
+    node.kind === Kind.SCHEMA_EXTENSION ||
+    node.kind === Kind.DIRECTIVE_EXTENSION ||
+    isTypeExtensionNode(node)
+  );
 }
 
 export function isTypeExtensionNode(node: ASTNode): node is TypeExtensionNode {