[RFC] Directives in schema language

This adds directives to schema language and to the utilities that use it (schema parser, and buildASTSchema). Directives are one of the few missing pieces from representing a full schema in the schema language.

Note: the schema language is still experimental, so there is no corresponding change to the spec yet.

DirectiveDefinition :
  - directive @ Name ArgumentsDefinition? on DirectiveLocations

DirectiveLocations :
  - Name
  - DirectiveLocations | Name

Example:

```
directive @Skip(if: Boolean!) on FIELD | FRAGMENT_SPREAD | INLINE_FRAGMENT

directive @include(if: Boolean!)
  on FIELD
   | FRAGMENT_SPREAD
   | INLINE_FRAGMENT
```

Author: leebyron

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

@@ -36,3 +36,10 @@ input InputType {
 extend type Foo {
   seven(argument: [String]): Type
 }
+
+directive @skip(if: Boolean!) on FIELD | FRAGMENT_SPREAD | INLINE_FRAGMENT
+
+directive @include(if: Boolean!)
+  on FIELD
+   | FRAGMENT_SPREAD
+   | INLINE_FRAGMENT

src/language/__tests__/schema-printer.js

@@ -49,6 +49,7 @@ describe('Printer', () => {
 
     const printed = print(ast);
 
+    /* eslint-disable max-len */
     expect(printed).to.equal(
 `type Foo implements Bar {
   one: Type
@@ -81,6 +82,10 @@ input InputType {
 extend type Foo {
   seven(argument: [String]): Type
 }
+
+directive @skip(if: Boolean!) on FIELD | FRAGMENT_SPREAD | INLINE_FRAGMENT
+
+directive @include(if: Boolean!) on FIELD | FRAGMENT_SPREAD | INLINE_FRAGMENT
 `);
 
   });

src/language/ast.js

@@ -57,6 +57,7 @@ export type Node = Name
                  | EnumValueDefinition
                  | InputObjectTypeDefinition
                  | TypeExtensionDefinition
+                 | DirectiveDefinition
 
 // Name
 
@@ -78,6 +79,7 @@ export type Definition = OperationDefinition
                        | FragmentDefinition
                        | TypeDefinition
                        | TypeExtensionDefinition
+                       | DirectiveDefinition
 
 export type OperationDefinition = {
   kind: 'OperationDefinition';
@@ -332,3 +334,11 @@ export type TypeExtensionDefinition = {
   loc?: ?Location;
   definition: ObjectTypeDefinition;
 }
+
+export type DirectiveDefinition = {
+  kind: 'DirectiveDefinition';
+  loc?: ?Location;
+  name: Name;
+  arguments?: ?Array<InputValueDefinition>;
+  locations: Array<Name>;
+}

src/language/kinds.js

@@ -59,4 +59,11 @@ export const SCALAR_TYPE_DEFINITION = 'ScalarTypeDefinition';
 export const ENUM_TYPE_DEFINITION = 'EnumTypeDefinition';
 export const ENUM_VALUE_DEFINITION = 'EnumValueDefinition';
 export const INPUT_OBJECT_TYPE_DEFINITION = 'InputObjectTypeDefinition';
+
+// Type Extensions
+
 export const TYPE_EXTENSION_DEFINITION = 'TypeExtensionDefinition';
+
+// Directive Definitions
+
+export const DIRECTIVE_DEFINITION = 'DirectiveDefinition';

src/language/parser.js

@@ -51,6 +51,8 @@ import type {
   InputObjectTypeDefinition,
 
   TypeExtensionDefinition,
+
+  DirectiveDefinition,
 } from './ast';
 
 import {
@@ -94,6 +96,8 @@ import {
   INPUT_OBJECT_TYPE_DEFINITION,
 
   TYPE_EXTENSION_DEFINITION,
+
+  DIRECTIVE_DEFINITION,
 } from './kinds';
 
 
@@ -205,6 +209,7 @@ function parseDefinition(parser: Parser): Definition {
       case 'enum':
       case 'input': return parseTypeDefinition(parser);
       case 'extend': return parseTypeExtensionDefinition(parser);
+      case 'directive': return parseDirectiveDefinition(parser);
     }
   }
 
@@ -898,6 +903,39 @@ function parseTypeExtensionDefinition(parser: Parser): TypeExtensionDefinition {
   };
 }
 
+/**
+ * DirectiveDefinition :
+ *   - directive @ Name ArgumentsDefinition? on DirectiveLocations
+ */
+function parseDirectiveDefinition(parser: Parser): DirectiveDefinition {
+  const start = parser.token.start;
+  expectKeyword(parser, 'directive');
+  expect(parser, TokenKind.AT);
+  const name = parseName(parser);
+  const args = parseArgumentDefs(parser);
+  expectKeyword(parser, 'on');
+  const locations = parseDirectiveLocations(parser);
+  return {
+    kind: DIRECTIVE_DEFINITION,
+    name,
+    arguments: args,
+    locations,
+    loc: loc(parser, start)
+  };
+}
+
+/**
+ * DirectiveLocations :
+ *   - Name
+ *   - DirectiveLocations | Name
+ */
+function parseDirectiveLocations(parser: Parser): Array<Name> {
+  const locations = [];
+  do {
+    locations.push(parseName(parser));
+  } while (skip(parser, TokenKind.PIPE));
+  return locations;
+}
 
 // Core parsing utility functions
 

src/language/printer.js

@@ -123,6 +123,10 @@ const printDocASTReducer = {
     `input ${name} ${block(fields)}`,
 
   TypeExtensionDefinition: ({ definition }) => `extend ${definition}`,
+
+  DirectiveDefinition: ({ name, arguments: args, locations }) =>
+    'directive @' + name + wrap('(', join(args, ', '), ')') +
+    ' on ' + join(locations, ' | '),
 };
 
 /**

src/language/visitor.js

@@ -48,6 +48,7 @@ export const QueryDocumentKeys = {
   EnumValueDefinition: [ 'name' ],
   InputObjectTypeDefinition: [ 'name', 'fields' ],
   TypeExtensionDefinition: [ 'definition' ],
+  DirectiveDefinition: [ 'name', 'arguments', 'locations' ],
 };
 
 export const BREAK = {};

src/type/directives.js

@@ -8,8 +8,11 @@
  *  of patent rights can be found in the PATENTS file in the same directory.
  */
 
-import { GraphQLNonNull } from './definition';
-import type { GraphQLArgument } from './definition';
+import { isInputType, GraphQLNonNull } from './definition';
+import type {
+  GraphQLFieldConfigArgumentMap,
+  GraphQLArgument
+} from './definition';
 import { GraphQLBoolean } from './scalars';
 import invariant from '../jsutils/invariant';
 import { assertValidName } from '../utilities/assertValidName';
@@ -47,15 +50,39 @@ export class GraphQLDirective {
     this.name = config.name;
     this.description = config.description;
     this.locations = config.locations;
-    this.args = config.args || [];
+
+    const args = config.args;
+    if (!args) {
+      this.args = [];
+    } else {
+      invariant(
+        !Array.isArray(args),
+        `@${config.name} args must be an object with argument names as keys.`
+      );
+      this.args = Object.keys(args).map(argName => {
+        assertValidName(argName);
+        const arg = args[argName];
+        invariant(
+          isInputType(arg.type),
+          `@${config.name}(${argName}:) argument type must be ` +
+          `Input Type but got: ${arg.type}.`
+        );
+        return {
+          name: argName,
+          description: arg.description === undefined ? null : arg.description,
+          type: arg.type,
+          defaultValue: arg.defaultValue === undefined ? null : arg.defaultValue
+        };
+      });
+    }
   }
 }
 
 type GraphQLDirectiveConfig = {
   name: string;
   description?: ?string;
   locations: Array<DirectiveLocationEnum>;
-  args?: ?Array<GraphQLArgument>;
+  args?: ?GraphQLFieldConfigArgumentMap;
 }
 
 /**
@@ -71,11 +98,12 @@ export const GraphQLIncludeDirective = new GraphQLDirective({
     DirectiveLocation.FRAGMENT_SPREAD,
     DirectiveLocation.INLINE_FRAGMENT,
   ],
-  args: [
-    { name: 'if',
+  args: {
+    if: {
       type: new GraphQLNonNull(GraphQLBoolean),
-      description: 'Included when true.' }
-  ],
+      description: 'Included when true.'
+    }
+  },
 });
 
 /**
@@ -91,9 +119,10 @@ export const GraphQLSkipDirective = new GraphQLDirective({
     DirectiveLocation.FRAGMENT_SPREAD,
     DirectiveLocation.INLINE_FRAGMENT,
   ],
-  args: [
-    { name: 'if',
+  args: {
+    if: {
       type: new GraphQLNonNull(GraphQLBoolean),
-      description: 'Skipped when true.' }
-  ],
+      description: 'Skipped when true.'
+    }
+  },
 });

src/utilities/__tests__/buildASTSchema.js

@@ -41,6 +41,18 @@ type HelloScalars {
     expect(output).to.equal(body);
   });
 
+  it('With directives', () => {
+    const body = `
+directive @foo(arg: Int) on FIELD
+
+type Hello {
+  str: String
+}
+`;
+    const output = cycleOutput(body, 'Hello');
+    expect(output).to.equal(body);
+  });
+
   it('Type modifiers', () => {
     const body = `
 type HelloScalars {

src/utilities/__tests__/schemaPrinter.js

@@ -508,6 +508,10 @@ type Root {
     const Schema = new GraphQLSchema({ query: Root });
     const output = '\n' + printIntrospectionSchema(Schema);
     const introspectionSchema = `
+directive @include(if: Boolean!) on FIELD | FRAGMENT_SPREAD | INLINE_FRAGMENT
+
+directive @skip(if: Boolean!) on FIELD | FRAGMENT_SPREAD | INLINE_FRAGMENT
+
 type __Directive {
   name: String!
   description: String