Add oneOf directive

This adds the @OneOf directive as a default directive to indicate
Objects and Input Objects as OneOf Objects/Input Objects which ensure
there is exactly one non-null entry. Future commits will work to
implement this directive.

Author: erikkessler1

src/index.ts

@@ -64,6 +64,7 @@ export {
   GraphQLSkipDirective,
   GraphQLDeprecatedDirective,
   GraphQLSpecifiedByDirective,
+  GraphQLOneOfDirective,
   // "Enum" of Type Kinds
   TypeKind,
   // Constant Deprecation Reason

src/type/__tests__/introspection-test.ts

@@ -989,6 +989,12 @@ describe('Introspection', () => {
                 },
               ],
             },
+            {
+              name: 'oneOf',
+              isRepeatable: false,
+              locations: ['OBJECT', 'INPUT_OBJECT'],
+              args: [],
+            },
           ],
         },
       },

src/type/directives.ts

@@ -209,6 +209,17 @@ export const GraphQLSpecifiedByDirective: GraphQLDirective =
     },
   });
 
+/**
+ * Used to declare an Input Object as a OneOf Input Objects and an Object as a OneOf Object.
+ */
+export const GraphQLOneOfDirective: GraphQLDirective = new GraphQLDirective({
+  name: 'oneOf',
+  description:
+    'Indicates an Object is a OneOf Object or an Input Object is a OneOf Input Object.',
+  locations: [DirectiveLocation.OBJECT, DirectiveLocation.INPUT_OBJECT],
+  args: {},
+});
+
 /**
  * The full list of specified directives.
  */
@@ -218,6 +229,7 @@ export const specifiedDirectives: ReadonlyArray<GraphQLDirective> =
     GraphQLSkipDirective,
     GraphQLDeprecatedDirective,
     GraphQLSpecifiedByDirective,
+    GraphQLOneOfDirective,
   ]);
 
 export function isSpecifiedDirective(directive: GraphQLDirective): boolean {

src/type/index.ts

@@ -133,6 +133,7 @@ export {
   GraphQLSkipDirective,
   GraphQLDeprecatedDirective,
   GraphQLSpecifiedByDirective,
+  GraphQLOneOfDirective,
   // Constant Deprecation Reason
   DEFAULT_DEPRECATION_REASON,
 } from './directives';

src/utilities/__tests__/buildASTSchema-test.ts

@@ -23,6 +23,7 @@ import {
   assertDirective,
   GraphQLDeprecatedDirective,
   GraphQLIncludeDirective,
+  GraphQLOneOfDirective,
   GraphQLSkipDirective,
   GraphQLSpecifiedByDirective,
 } from '../../type/directives';
@@ -222,7 +223,7 @@ describe('Schema Builder', () => {
   it('Maintains @include, @skip & @specifiedBy', () => {
     const schema = buildSchema('type Query');
 
-    expect(schema.getDirectives()).to.have.lengthOf(4);
+    expect(schema.getDirectives()).to.have.lengthOf(5);
     expect(schema.getDirective('skip')).to.equal(GraphQLSkipDirective);
     expect(schema.getDirective('include')).to.equal(GraphQLIncludeDirective);
     expect(schema.getDirective('deprecated')).to.equal(
@@ -231,6 +232,7 @@ describe('Schema Builder', () => {
     expect(schema.getDirective('specifiedBy')).to.equal(
       GraphQLSpecifiedByDirective,
     );
+    expect(schema.getDirective('oneOf')).to.equal(GraphQLOneOfDirective);
   });
 
   it('Overriding directives excludes specified', () => {
@@ -239,9 +241,10 @@ describe('Schema Builder', () => {
       directive @include on FIELD
       directive @deprecated on FIELD_DEFINITION
       directive @specifiedBy on FIELD_DEFINITION
+      directive @oneOf on OBJECT
     `);
 
-    expect(schema.getDirectives()).to.have.lengthOf(4);
+    expect(schema.getDirectives()).to.have.lengthOf(5);
     expect(schema.getDirective('skip')).to.not.equal(GraphQLSkipDirective);
     expect(schema.getDirective('include')).to.not.equal(
       GraphQLIncludeDirective,
@@ -252,18 +255,20 @@ describe('Schema Builder', () => {
     expect(schema.getDirective('specifiedBy')).to.not.equal(
       GraphQLSpecifiedByDirective,
     );
+    expect(schema.getDirective('oneOf')).to.not.equal(GraphQLOneOfDirective);
   });
 
-  it('Adding directives maintains @include, @skip & @specifiedBy', () => {
+  it('Adding directives maintains @include, @skip, @deprecated, @specifiedBy, and @oneOf', () => {
     const schema = buildSchema(`
       directive @foo(arg: Int) on FIELD
     `);
 
-    expect(schema.getDirectives()).to.have.lengthOf(5);
+    expect(schema.getDirectives()).to.have.lengthOf(6);
     expect(schema.getDirective('skip')).to.not.equal(undefined);
     expect(schema.getDirective('include')).to.not.equal(undefined);
     expect(schema.getDirective('deprecated')).to.not.equal(undefined);
     expect(schema.getDirective('specifiedBy')).to.not.equal(undefined);
+    expect(schema.getDirective('oneOf')).to.not.equal(undefined);
   });
 
   it('Type modifiers', () => {

src/utilities/__tests__/findBreakingChanges-test.ts

@@ -4,6 +4,7 @@ import { describe, it } from 'mocha';
 import {
   GraphQLDeprecatedDirective,
   GraphQLIncludeDirective,
+  GraphQLOneOfDirective,
   GraphQLSkipDirective,
   GraphQLSpecifiedByDirective,
 } from '../../type/directives';
@@ -802,6 +803,7 @@ describe('findBreakingChanges', () => {
         GraphQLSkipDirective,
         GraphQLIncludeDirective,
         GraphQLSpecifiedByDirective,
+        GraphQLOneOfDirective,
       ],
     });
 

src/utilities/__tests__/printSchema-test.ts

@@ -656,6 +656,11 @@ describe('Type System Printer', () => {
         url: String!
       ) on SCALAR
 
+      """
+      Indicates an Object is a OneOf Object or an Input Object is a OneOf Input Object.
+      """
+      directive @oneOf on OBJECT | INPUT_OBJECT
+
       """
       A GraphQL Schema defines the capabilities of a GraphQL server. It exposes all available types and directives on the server, as well as the entry points for query, mutation, and subscription operations.
       """