fix: suppress records for deferred fragments that are completely empty (graphql#3984)

i.e. no fields and no enclosed deferred fragments

These fragments can be thought of to be completely skipped, because
including them will just result in emitting metadata but no actual data.
Alternatively, these fragments can be thought of as being inlined.

This could probably be considered a bug fix, in that Example F @
graphql/defer-stream-wg#69 explicitly
states that these fragments should be skipped.

Author: yaacovCR

src/execution/IncrementalPublisher.ts

@@ -666,10 +666,13 @@ export class IncrementalPublisher {
       return;
     }
 
-    if (subsequentResultRecord._pending.size === 0) {
-      this._push(subsequentResultRecord);
-    } else {
+    if (subsequentResultRecord._pending.size > 0) {
       this._introduce(subsequentResultRecord);
+    } else if (
+      subsequentResultRecord.deferredGroupedFieldSetRecords.size > 0 ||
+      subsequentResultRecord.children.size > 0
+    ) {
+      this._push(subsequentResultRecord);
     }
   }
 

src/execution/__tests__/defer-test.ts

@@ -394,21 +394,13 @@ describe('Execute: defer directive', () => {
       }
     `);
     const result = await complete(document);
-    expectJSON(result).toDeepEqual([
-      {
-        data: {
-          hero: {
-            name: 'Luke',
-          },
+    expectJSON(result).toDeepEqual({
+      data: {
+        hero: {
+          name: 'Luke',
         },
-        pending: [{ id: '0', path: ['hero'], label: 'DeferTop' }],
-        hasNext: true,
-      },
-      {
-        completed: [{ id: '0' }],
-        hasNext: false,
       },
-    ]);
+    });
   });
   it('Can defer a fragment that is also not deferred, non-deferred fragment is first', async () => {
     const document = parse(`
@@ -423,21 +415,13 @@ describe('Execute: defer directive', () => {
       }
     `);
     const result = await complete(document);
-    expectJSON(result).toDeepEqual([
-      {
-        data: {
-          hero: {
-            name: 'Luke',
-          },
+    expectJSON(result).toDeepEqual({
+      data: {
+        hero: {
+          name: 'Luke',
         },
-        pending: [{ id: '0', path: ['hero'], label: 'DeferTop' }],
-        hasNext: true,
-      },
-      {
-        completed: [{ id: '0' }],
-        hasNext: false,
       },
-    ]);
+    });
   });
 
   it('Can defer an inline fragment', async () => {
@@ -481,19 +465,11 @@ describe('Execute: defer directive', () => {
       }
     `);
     const result = await complete(document);
-    expectJSON(result).toDeepEqual([
-      {
-        data: {
-          hero: {},
-        },
-        pending: [{ id: '0', path: ['hero'] }],
-        hasNext: true,
-      },
-      {
-        completed: [{ id: '0' }],
-        hasNext: false,
+    expectJSON(result).toDeepEqual({
+      data: {
+        hero: {},
       },
-    ]);
+    });
   });
 
   it('Can separately emit defer fragments with different labels with varying fields', async () => {
@@ -775,40 +751,18 @@ describe('Execute: defer directive', () => {
         data: { hero: { friends: [{}, {}, {}] } },
         pending: [
           { id: '0', path: ['hero', 'friends', 0] },
-          { id: '1', path: ['hero', 'friends', 0] },
-          { id: '2', path: ['hero', 'friends', 0] },
-          { id: '3', path: ['hero', 'friends', 0] },
-          { id: '4', path: ['hero', 'friends', 1] },
-          { id: '5', path: ['hero', 'friends', 1] },
-          { id: '6', path: ['hero', 'friends', 1] },
-          { id: '7', path: ['hero', 'friends', 1] },
-          { id: '8', path: ['hero', 'friends', 2] },
-          { id: '9', path: ['hero', 'friends', 2] },
-          { id: '10', path: ['hero', 'friends', 2] },
-          { id: '11', path: ['hero', 'friends', 2] },
+          { id: '1', path: ['hero', 'friends', 1] },
+          { id: '2', path: ['hero', 'friends', 2] },
         ],
         hasNext: true,
       },
       {
         incremental: [
           { data: { id: '2', name: 'Han' }, id: '0' },
-          { data: { id: '3', name: 'Leia' }, id: '4' },
-          { data: { id: '4', name: 'C-3PO' }, id: '8' },
-        ],
-        completed: [
-          { id: '1' },
-          { id: '2' },
-          { id: '3' },
-          { id: '5' },
-          { id: '6' },
-          { id: '7' },
-          { id: '9' },
-          { id: '10' },
-          { id: '11' },
-          { id: '0' },
-          { id: '4' },
-          { id: '8' },
+          { data: { id: '3', name: 'Leia' }, id: '1' },
+          { data: { id: '4', name: 'C-3PO' }, id: '2' },
         ],
+        completed: [{ id: '0' }, { id: '1' }, { id: '2' }],
         hasNext: false,
       },
     ]);
@@ -1494,21 +1448,13 @@ describe('Execute: defer directive', () => {
       }
     `);
     const result = await complete(document);
-    expectJSON(result).toDeepEqual([
-      {
-        data: {
-          hero: {
-            friends: [{ name: 'Han' }, { name: 'Leia' }, { name: 'C-3PO' }],
-          },
+    expectJSON(result).toDeepEqual({
+      data: {
+        hero: {
+          friends: [{ name: 'Han' }, { name: 'Leia' }, { name: 'C-3PO' }],
         },
-        pending: [{ id: '0', path: ['hero'] }],
-        hasNext: true,
       },
-      {
-        completed: [{ id: '0' }],
-        hasNext: false,
-      },
-    ]);
+    });
   });
 
   it('Deduplicates async iterable list fields', async () => {
@@ -1534,17 +1480,9 @@ describe('Execute: defer directive', () => {
         },
       },
     });
-    expectJSON(result).toDeepEqual([
-      {
-        data: { hero: { friends: [{ name: 'Han' }] } },
-        pending: [{ id: '0', path: ['hero'] }],
-        hasNext: true,
-      },
-      {
-        completed: [{ id: '0' }],
-        hasNext: false,
-      },
-    ]);
+    expectJSON(result).toDeepEqual({
+      data: { hero: { friends: [{ name: 'Han' }] } },
+    });
   });
 
   it('Deduplicates empty async iterable list fields', async () => {
@@ -1571,17 +1509,9 @@ describe('Execute: defer directive', () => {
         },
       },
     });
-    expectJSON(result).toDeepEqual([
-      {
-        data: { hero: { friends: [] } },
-        pending: [{ id: '0', path: ['hero'] }],
-        hasNext: true,
-      },
-      {
-        completed: [{ id: '0' }],
-        hasNext: false,
-      },
-    ]);
+    expectJSON(result).toDeepEqual({
+      data: { hero: { friends: [] } },
+    });
   });
 
   it('Does not deduplicate list fields with non-overlapping fields', async () => {
@@ -1655,17 +1585,9 @@ describe('Execute: defer directive', () => {
         friends: () => [],
       },
     });
-    expectJSON(result).toDeepEqual([
-      {
-        data: { hero: { friends: [] } },
-        pending: [{ id: '0', path: ['hero'] }],
-        hasNext: true,
-      },
-      {
-        completed: [{ id: '0' }],
-        hasNext: false,
-      },
-    ]);
+    expectJSON(result).toDeepEqual({
+      data: { hero: { friends: [] } },
+    });
   });
 
   it('Deduplicates null object fields', async () => {
@@ -1689,17 +1611,9 @@ describe('Execute: defer directive', () => {
         nestedObject: () => null,
       },
     });
-    expectJSON(result).toDeepEqual([
-      {
-        data: { hero: { nestedObject: null } },
-        pending: [{ id: '0', path: ['hero'] }],
-        hasNext: true,
-      },
-      {
-        completed: [{ id: '0' }],
-        hasNext: false,
-      },
-    ]);
+    expectJSON(result).toDeepEqual({
+      data: { hero: { nestedObject: null } },
+    });
   });
 
   it('Deduplicates promise object fields', async () => {
@@ -1722,17 +1636,9 @@ describe('Execute: defer directive', () => {
         nestedObject: () => Promise.resolve({ name: 'foo' }),
       },
     });
-    expectJSON(result).toDeepEqual([
-      {
-        data: { hero: { nestedObject: { name: 'foo' } } },
-        pending: [{ id: '0', path: ['hero'] }],
-        hasNext: true,
-      },
-      {
-        completed: [{ id: '0' }],
-        hasNext: false,
-      },
-    ]);
+    expectJSON(result).toDeepEqual({
+      data: { hero: { nestedObject: { name: 'foo' } } },
+    });
   });
 
   it('Handles errors thrown in deferred fragments', async () => {

src/execution/__tests__/stream-test.ts

@@ -1780,33 +1780,29 @@ describe('Execute: stream directive', () => {
             nestedFriendList: [],
           },
         },
-        pending: [
-          { id: '0', path: ['nestedObject'] },
-          { id: '1', path: ['nestedObject', 'nestedFriendList'] },
-        ],
+        pending: [{ id: '0', path: ['nestedObject', 'nestedFriendList'] }],
         hasNext: true,
       },
       {
         incremental: [
           {
             items: [{ id: '1', name: 'Luke' }],
-            id: '1',
+            id: '0',
           },
         ],
-        completed: [{ id: '0' }],
         hasNext: true,
       },
       {
         incremental: [
           {
             items: [{ id: '2', name: 'Han' }],
-            id: '1',
+            id: '0',
           },
         ],
         hasNext: true,
       },
       {
-        completed: [{ id: '1' }],
+        completed: [{ id: '0' }],
         hasNext: false,
       },
     ]);