Avoid throwing in the DeclarativeMutationHandler when the server returns null

Reviewed By: jstejada

Differential Revision: D25553388

fbshipit-source-id: 63e92372bbccf439703478d017bdf72817d16f07

Author: tyao1

packages/relay-runtime/handlers/connection/MutationHandlers.js

@@ -105,6 +105,13 @@ function edgeUpdater(
       'MutationHandlers: Expected connection IDs to be specified.',
     );
     const serverEdge = record.getLinkedRecord(payload.fieldKey, payload.args);
+    if (serverEdge == null) {
+      warning(
+        false,
+        'MutationHandlers: Expected the server edge to be non-null',
+      );
+      return;
+    }
     for (const connectionID of connections) {
       const connection = store.get(connectionID);
       if (connection == null) {
@@ -155,10 +162,10 @@ function nodeUpdater(
         serverNodes = record.getLinkedRecords(payload.fieldKey, payload.args);
       } catch {}
     }
-    invariant(
-      singleServerNode != null || serverNodes != null,
-      'MutationHandlers: Expected target node to exist.',
-    );
+    if (singleServerNode == null && serverNodes == null) {
+      warning(false, 'MutationHandlers: Expected target node to exist.');
+      return;
+    }
     const serverNodeList = serverNodes ?? [singleServerNode];
     for (const serverNode of serverNodeList) {
       if (serverNode == null) {

packages/relay-runtime/store/__tests__/RelayModernEnvironment-ExecuteMutationWithDeclarativeMutation-test.js

@@ -19,6 +19,8 @@ const RelayNetwork = require('../../network/RelayNetwork');
 const RelayObservable = require('../../network/RelayObservable');
 const RelayRecordSource = require('../RelayRecordSource');
 
+const warning = require('warning');
+
 const {
   createOperationDescriptor,
 } = require('../RelayModernOperationDescriptor');
@@ -1743,4 +1745,31 @@ describe('connection node mutations', () => {
       },
     ]);
   });
+
+  it('warns when the server returns an null for the node', () => {
+    const snapshot = environment.lookup(operation.fragment);
+    const callback = jest.fn();
+    environment.subscribe(snapshot, callback);
+
+    environment
+      .executeMutation({
+        operation: appendWithLiteralEdgeOperation,
+      })
+      .subscribe(callbacks);
+
+    callback.mockClear();
+    subject.next({
+      data: {
+        commentCreate: {
+          comment: null,
+        },
+      },
+    });
+    subject.complete();
+    expect(callback.mock.calls.length).toBe(0);
+    expect(warning).toBeCalledWith(
+      false,
+      'MutationHandlers: Expected target node to exist.',
+    );
+  });
 });