create_user: Handle integrity error when importing settings.

During account creation when a user opted to import settings
from an existing account, the "Mark visibility_policy_banner as
read" step was raising integrity error.

It is because 'copy_onboarding_steps' is already executed earlier
in the 'do_create_user' codeflow. If the source profile had already
marked 'visibility_policy_banner' as read, we were facing integrity
error.

This commit fixes the bug.

zerver/actions/create_user.py

@@ -1,10 +1,11 @@
 from collections import defaultdict
 from collections.abc import Iterable, Sequence
+from contextlib import suppress
 from datetime import timedelta
 from typing import Any
 
 from django.conf import settings
-from django.db import transaction
+from django.db import IntegrityError, transaction
 from django.db.models import F
 from django.utils.timezone import now as timezone_now
 from django.utils.translation import gettext as _
@@ -351,7 +352,17 @@ def process_new_human_user(
 
     # The 'visibility_policy_banner' is only displayed to existing users.
     # Mark it as read for a new user.
-    OnboardingStep.objects.create(user=user_profile, onboarding_step="visibility_policy_banner")
+    #
+    # If the new user opted to import settings from an existing account, and
+    # 'visibility_policy_banner' is already marked as read for the existing account,
+    # 'copy_onboarding_steps' function already did the needed copying.
+    # Simply ignore the IntegrityError in that case.
+    #
+    # The extremely brief nature of this subtransaction makes a savepoint safe.
+    # See https://postgres.ai/blog/20210831-postgresql-subtransactions-considered-harmful
+    # for context on risks around savepoints.
+    with suppress(IntegrityError), transaction.atomic(savepoint=True):
+        OnboardingStep.objects.create(user=user_profile, onboarding_step="visibility_policy_banner")
 
 
 def notify_created_user(user_profile: UserProfile, notify_user_ids: list[int]) -> None:

zerver/tests/test_signup.py

@@ -67,6 +67,7 @@ from zerver.models import (
     CustomProfileFieldValue,
     DefaultStream,
     Message,
+    OnboardingStep,
     OnboardingUserMessage,
     PreregistrationRealm,
     PreregistrationUser,
@@ -2826,6 +2827,9 @@ class UserSignUpTest(ZulipTestCase):
         hamlet_in_zulip.email_address_visibility = UserProfile.EMAIL_ADDRESS_VISIBILITY_EVERYONE
         hamlet_in_zulip.save()
 
+        OnboardingStep.objects.filter(user=hamlet_in_zulip).delete()
+        OnboardingStep.objects.create(user=hamlet_in_zulip, onboarding_step="intro_resolve_topic")
+
         result = self.client_post("/accounts/home/", {"email": email}, subdomain=subdomain)
         self.assertEqual(result.status_code, 302)
         result = self.client_get(result["Location"], subdomain=subdomain)
@@ -2844,6 +2848,12 @@ class UserSignUpTest(ZulipTestCase):
         self.assertEqual(hamlet.high_contrast_mode, False)
         self.assertEqual(hamlet.enable_stream_audible_notifications, False)
         self.assertEqual(hamlet.enter_sends, False)
+        # 'visibility_policy_banner' is marked as read in 'process_new_human_user'.
+        # 'copy_default_settings' is not executed as the user decided to NOT import
+        # settings from another realm, hence 'intro_resolve_topic' not marked as seen.
+        onboarding_steps = OnboardingStep.objects.filter(user=hamlet)
+        self.assertEqual(onboarding_steps.count(), 1)
+        self.assertEqual(onboarding_steps[0].onboarding_step, "visibility_policy_banner")
 
     def test_signup_with_user_settings_from_another_realm(self) -> None:
         hamlet_in_zulip = self.example_user("hamlet")
@@ -2864,6 +2874,12 @@ class UserSignUpTest(ZulipTestCase):
         hamlet_in_zulip.email_address_visibility = UserProfile.EMAIL_ADDRESS_VISIBILITY_EVERYONE
         hamlet_in_zulip.save()
 
+        OnboardingStep.objects.filter(user=hamlet_in_zulip).delete()
+        OnboardingStep.objects.create(user=hamlet_in_zulip, onboarding_step="intro_resolve_topic")
+        OnboardingStep.objects.create(
+            user=hamlet_in_zulip, onboarding_step="visibility_policy_banner"
+        )
+
         # Now we'll be making requests to another subdomain, so we need to logout
         # to avoid polluting the session in the test environment by still being
         # logged in.
@@ -2909,6 +2925,13 @@ class UserSignUpTest(ZulipTestCase):
         self.assertEqual(
             hamlet_in_lear.email_address_visibility, UserProfile.EMAIL_ADDRESS_VISIBILITY_NOBODY
         )
+        # Verify that 'copy_default_settings' copies the onboarding steps.
+        onboarding_steps = OnboardingStep.objects.filter(user=hamlet_in_lear)
+        self.assertEqual(onboarding_steps.count(), 2)
+        self.assertEqual(
+            set(onboarding_steps.values_list("onboarding_step", flat=True)),
+            {"intro_resolve_topic", "visibility_policy_banner"},
+        )
 
         zulip_path_id = avatar_disk_path(hamlet_in_zulip)
         lear_path_id = avatar_disk_path(hamlet_in_lear)