Implement support for @defer directive

Author: robrichard

src/execution/__tests__/defer-test.ts

@@ -0,0 +1,271 @@
+import { describe, it } from 'mocha';
+
+import { expectJSON } from '../../__testUtils__/expectJSON';
+import { isAsyncIterable } from '../../jsutils/isAsyncIterable';
+import { parse } from '../../language/parser';
+
+import { GraphQLID, GraphQLString } from '../../type/scalars';
+import { GraphQLSchema } from '../../type/schema';
+import { GraphQLObjectType, GraphQLList } from '../../type/definition';
+
+import type { DocumentNode } from '../../language/ast';
+
+import { execute } from '../execute';
+
+const friendType = new GraphQLObjectType({
+  fields: {
+    id: { type: GraphQLID },
+    name: { type: GraphQLString },
+  },
+  name: 'Friend',
+});
+
+const friends = [
+  { name: 'Han', id: 2 },
+  { name: 'Leia', id: 3 },
+  { name: 'C-3PO', id: 4 },
+];
+
+const heroType = new GraphQLObjectType({
+  fields: {
+    id: { type: GraphQLID },
+    name: { type: GraphQLString },
+    errorField: {
+      type: GraphQLString,
+      resolve: () => {
+        throw new Error('bad');
+      },
+    },
+    friends: {
+      type: new GraphQLList(friendType),
+      resolve: () => friends,
+    },
+  },
+  name: 'Hero',
+});
+
+const hero = { name: 'Luke', id: 1 };
+
+const query = new GraphQLObjectType({
+  fields: {
+    hero: {
+      type: heroType,
+      resolve: () => hero,
+    },
+  },
+  name: 'Query',
+});
+
+async function complete(document: DocumentNode) {
+  const schema = new GraphQLSchema({ query });
+
+  const result = await execute({
+    schema,
+    document,
+    rootValue: {},
+  });
+
+  if (isAsyncIterable(result)) {
+    const results = [];
+    for await (const patch of result) {
+      results.push(patch);
+    }
+    return results;
+  }
+  return result;
+}
+
+describe('Execute: defer directive', () => {
+  it('Can defer fragments containing scalar types', async () => {
+    const document = parse(`
+      query HeroNameQuery {
+        hero {
+          id
+          ...NameFragment @defer
+        }
+      }
+      fragment NameFragment on Hero {
+        id
+        name
+      }
+    `);
+    const result = await complete(document);
+
+    expectJSON(result).toDeepEqual([
+      {
+        data: {
+          hero: {
+            id: '1',
+          },
+        },
+        hasNext: true,
+      },
+      {
+        data: {
+          id: '1',
+          name: 'Luke',
+        },
+        path: ['hero'],
+        hasNext: false,
+      },
+    ]);
+  });
+  it('Can disable defer using if argument', async () => {
+    const document = parse(`
+      query HeroNameQuery {
+        hero {
+          id
+          ...NameFragment @defer(if: false)
+        }
+      }
+      fragment NameFragment on Hero {
+        name
+      }
+    `);
+    const result = await complete(document);
+
+    expectJSON(result).toDeepEqual({
+      data: {
+        hero: {
+          id: '1',
+          name: 'Luke',
+        },
+      },
+    });
+  });
+  it('Can defer fragments containing on the top level Query field', async () => {
+    const document = parse(`
+      query HeroNameQuery {
+        ...QueryFragment @defer(label: "DeferQuery")
+      }
+      fragment QueryFragment on Query {
+        hero {
+          id
+        }
+      }
+    `);
+    const result = await complete(document);
+
+    expectJSON(result).toDeepEqual([
+      {
+        data: {},
+        hasNext: true,
+      },
+      {
+        data: {
+          hero: {
+            id: '1',
+          },
+        },
+        path: [],
+        label: 'DeferQuery',
+        hasNext: false,
+      },
+    ]);
+  });
+  it('Can defer a fragment within an already deferred fragment', async () => {
+    const document = parse(`
+      query HeroNameQuery {
+        hero {
+          id
+          ...TopFragment @defer(label: "DeferTop")
+        }
+      }
+      fragment TopFragment on Hero {
+        name
+        ...NestedFragment @defer(label: "DeferNested")
+      }
+      fragment NestedFragment on Hero {
+        friends {
+          name
+        }
+      }
+    `);
+    const result = await complete(document);
+
+    expectJSON(result).toDeepEqual([
+      {
+        data: {
+          hero: {
+            id: '1',
+          },
+        },
+        hasNext: true,
+      },
+      {
+        data: {
+          friends: [{ name: 'Han' }, { name: 'Leia' }, { name: 'C-3PO' }],
+        },
+        path: ['hero'],
+        label: 'DeferNested',
+        hasNext: true,
+      },
+      {
+        data: {
+          name: 'Luke',
+        },
+        path: ['hero'],
+        label: 'DeferTop',
+        hasNext: false,
+      },
+    ]);
+  });
+  it('Can defer an inline fragment', async () => {
+    const document = parse(`
+      query HeroNameQuery {
+        hero {
+          id
+          ... on Hero @defer(label: "InlineDeferred") {
+            name
+          }
+        }
+      }
+    `);
+    const result = await complete(document);
+
+    expectJSON(result).toDeepEqual([
+      {
+        data: { hero: { id: '1' } },
+        hasNext: true,
+      },
+      {
+        data: { name: 'Luke' },
+        path: ['hero'],
+        label: 'InlineDeferred',
+        hasNext: false,
+      },
+    ]);
+  });
+  it('Handles errors thrown in deferred fragments', async () => {
+    const document = parse(`
+      query HeroNameQuery {
+        hero {
+          id
+          ...NameFragment @defer
+        }
+      }
+      fragment NameFragment on Hero {
+        errorField
+      }
+    `);
+    const result = await complete(document);
+    expectJSON(result).toDeepEqual([
+      {
+        data: { hero: { id: '1' } },
+        hasNext: true,
+      },
+      {
+        data: { errorField: null },
+        path: ['hero'],
+        errors: [
+          {
+            message: 'bad',
+            locations: [{ line: 9, column: 9 }],
+            path: ['hero', 'errorField'],
+          },
+        ],
+        hasNext: false,
+      },
+    ]);
+  });
+});

src/execution/__tests__/lists-test.ts

@@ -12,7 +12,7 @@ import { GraphQLSchema } from '../../type/schema';
 
 import { buildSchema } from '../../utilities/buildASTSchema';
 
-import type { ExecutionResult } from '../execute';
+import type { ExecutionResult, AsyncExecutionResult } from '../execute';
 import { execute, executeSync } from '../execute';
 
 describe('Execute: Accepts any iterable as list value', () => {
@@ -83,7 +83,7 @@ describe('Execute: Accepts async iterables as list value', () => {
 
   function completeObjectList(
     resolve: GraphQLFieldResolver<{ index: number }, unknown>,
-  ): PromiseOrValue<ExecutionResult> {
+  ): PromiseOrValue<ExecutionResult | AsyncIterable<AsyncExecutionResult>> {
     const schema = new GraphQLSchema({
       query: new GraphQLObjectType({
         name: 'Query',