Fix cannot create task for new user via [] method

src/libs/actions/Report.ts

@@ -8,6 +8,7 @@ import Onyx from 'react-native-onyx';
 import type {PartialDeep, ValueOf} from 'type-fest';
 import type {Emoji} from '@assets/emojis/types';
 import type {FileObject} from '@components/AttachmentModal';
+import {FallbackAvatar} from '@components/Icon/Expensicons';
 import * as ActiveClientManager from '@libs/ActiveClientManager';
 import * as API from '@libs/API';
 import type {
@@ -3714,6 +3715,30 @@ function setGroupDraft(newGroupDraft: Partial<NewGroupChatDraft>) {
     Onyx.merge(ONYXKEYS.NEW_GROUP_CHAT_DRAFT, newGroupDraft);
 }
 
+function buildOptimisticTaskDataForNewAssingee(assigneeLogin: string) {
+    const assigneeAccountID = UserUtils.generateAccountID(assigneeLogin);
+    const report: OnyxEntry<Report> | undefined = ReportUtils.buildOptimisticChatReport([assigneeAccountID]);
+    report.isOptimisticReport = true;
+
+    // When assigning a task to a new user, by default we share the task in their DM
+    // However, the DM doesn't exist yet - and will be created optimistically once the task is created
+    // We don't want to show the new DM yet, because if you select an assignee and then change the assignee, the previous DM will still be shown
+    // So here, we create it optimistically to share it with the assignee, but we have to hide it until the task is created
+    if (report) {
+        report.isHidden = true;
+    }
+    Onyx.set(`${ONYXKEYS.COLLECTION.REPORT}${report.reportID}`, report);
+
+    const optimisticPersonalDetailsListAction = {
+        accountID: assigneeAccountID,
+        avatar: FallbackAvatar,
+        displayName: assigneeLogin,
+        login: assigneeLogin,
+    };
+    Onyx.merge(ONYXKEYS.PERSONAL_DETAILS_LIST, {[assigneeAccountID]: optimisticPersonalDetailsListAction});
+    return {assignee: optimisticPersonalDetailsListAction, assigneeReport: report};
+}
+
 export {
     searchInServer,
     addComment,
@@ -3797,4 +3822,5 @@ export {
     removeFromGroupChat,
     updateGroupChatMemberRoles,
     clearAddRoomMemberError,
+    buildOptimisticTaskDataForNewAssingee,
 };

src/pages/home/report/ReportFooter.tsx

@@ -109,10 +109,16 @@ function ReportFooter({
             const mentionWithDomain = ReportUtils.addDomainToShortMention(mention ?? '') ?? mention;
 
             let assignee: OnyxTypes.PersonalDetails | EmptyObject = {};
+            let assigneeChatReport;
             if (mentionWithDomain) {
                 assignee = Object.values(allPersonalDetails).find((value) => value?.login === mentionWithDomain) ?? {};
+                if (!Object.keys(assignee).length) {
+                    const optimisticDataForNewAssignee = Report.buildOptimisticTaskDataForNewAssingee(mentionWithDomain);
+                    assignee = optimisticDataForNewAssignee.assignee;
+                    assigneeChatReport = optimisticDataForNewAssignee.assigneeReport;
+                }
             }
-            Task.createTaskAndNavigate(report.reportID, title, '', assignee?.login ?? '', assignee.accountID, undefined, report.policyID);
+            Task.createTaskAndNavigate(report.reportID, title, '', assignee?.login ?? '', assignee.accountID, assigneeChatReport, report.policyID);
             return true;
         },
         [allPersonalDetails, report.policyID, report.reportID],