Service name uniqueness handled in all cases and tests passing.

app/main/forms.py

@@ -205,7 +205,24 @@ class AddServiceForm(Form):
 
 
 class ServiceNameForm(Form):
-    name = StringField(u'New name')
+    def __init__(self, names_func, *args, **kwargs):
+        """
+        Keyword arguments:
+        names_func -- Returns a list of unique service_names already registered
+        on the system.
+        """
+        self._names_func = names_func
+        super(ServiceNameForm, self).__init__(*args, **kwargs)
+
+    name = StringField(
+        u'New name',
+        validators=[
+            DataRequired(message='Service name can’t be empty')
+        ])
+
+    def validate_name(self, a):
+        if a.data in self._names_func():
+            raise ValidationError('This service name is already in use')
 
 
 class ConfirmPasswordForm(Form):

app/main/views/service_settings.py

@@ -18,7 +18,8 @@ from notifications_python_client.errors import HTTPError
 from app.main.dao.services_dao import (
     get_service_by_id,
     delete_service,
-    update_service
+    update_service,
+    find_all_service_names
 )
 
 from app.main import main
@@ -57,7 +58,7 @@ def service_name_change(service_id):
         else:
             raise e
 
-    form = ServiceNameForm()
+    form = ServiceNameForm(find_all_service_names)
 
     if form.validate_on_submit():
         session['service_name_change'] = form.name.data
@@ -89,10 +90,20 @@ def service_name_change_confirm(service_id):
 
     if form.validate_on_submit():
         service['name'] = session['service_name_change']
-        update_service(service)
-        session['service_name'] = service['name']
-        session.pop('service_name_change')
-        return redirect(url_for('.service_settings', service_id=service_id))
+        try:
+            update_service(service)
+        except HTTPError as e:
+            error_msg = "Duplicate service name '{}'".format(session['service_name_change'])
+            if e.status_code == 400 and error_msg in e.message['name']:
+                # Redirect the user back to the change service name screen
+                flash('This service name is already in use', 'error')
+                return redirect(url_for('main.service_name_change', service_id=service_id))
+            else:
+                raise e
+        else:
+            session['service_name'] = service['name']
+            session.pop('service_name_change')
+            return redirect(url_for('.service_settings', service_id=service_id))
     return render_template(
         'views/service-settings/confirm.html',
         heading='Change your service name',

tests/app/main/views/test_service_settings.py

@@ -54,8 +54,9 @@ def test_should_redirect_after_change_service_name(app_,
         with app_.test_client() as client:
             client.login(api_user_active)
             service_id = 123
-            response = client.post(url_for(
-                'main.service_name_change', service_id=service_id))
+            response = client.post(
+                url_for('main.service_name_change', service_id=service_id),
+                data={'name': "new name"})
 
         assert response.status_code == 302
         settings_url = url_for(
@@ -64,6 +65,27 @@ def test_should_redirect_after_change_service_name(app_,
         assert mock_get_service.called
 
 
+def test_should_not_allow_duplicate_names(app_,
+                                          api_user_active,
+                                          mock_get_service,
+                                          mock_get_user,
+                                          mock_get_user_by_email,
+                                          mock_login,
+                                          mock_has_permissions,
+                                          mock_get_services):
+    with app_.test_request_context():
+        with app_.test_client() as client:
+            client.login(api_user_active)
+            service_id = 123
+            response = client.post(
+                url_for('main.service_name_change', service_id=service_id),
+                data={'name': "service_one"})
+
+        assert response.status_code == 200
+        resp_data = response.get_data(as_text=True)
+        assert 'This service name is already in use' in resp_data
+
+
 def test_should_show_service_name_confirmation(app_,
                                                api_user_active,
                                                mock_get_service,
@@ -112,6 +134,32 @@ def test_should_redirect_after_service_name_confirmation(app_,
         assert mock_update_service.called
 
 
+def test_should_raise_duplicate_name_handled(app_,
+                                             api_user_active,
+                                             mock_get_service,
+                                             mock_update_service_raise_httperror_duplicate_name,
+                                             mock_get_user,
+                                             mock_get_user_by_email,
+                                             mock_login,
+                                             mock_verify_password,
+                                             mock_has_permissions):
+    with app_.test_request_context():
+        with app_.test_client() as client:
+            client.login(api_user_active)
+            service_id = 123
+            service_new_name = 'New Name'
+            with client.session_transaction() as session:
+                session['service_name_change'] = service_new_name
+            response = client.post(url_for(
+                'main.service_name_change_confirm', service_id=service_id))
+
+        assert response.status_code == 302
+        name_change_url = url_for(
+            'main.service_name_change', service_id=service_id, _external=True)
+        resp_data = response.get_data(as_text=True)
+        assert name_change_url == response.location
+
+
 def test_should_show_request_to_go_live(app_,
                                         api_user_active,
                                         mock_get_service,

tests/conftest.py

@@ -1,5 +1,6 @@
 import uuid
 from datetime import date, datetime, timedelta
+from unittest.mock import Mock
 import pytest
 
 from app import create_app
@@ -18,6 +19,8 @@ from app.notify_client.models import (
     InvitedUser
 )
 
+from notifications_python_client.errors import HTTPError
+
 
 @pytest.fixture(scope='session')
 def app_(request):
@@ -90,6 +93,24 @@ def mock_update_service(mocker):
         'app.notifications_api_client.update_service', side_effect=_update)
 
 
+@pytest.fixture(scope='function')
+def mock_update_service_raise_httperror_duplicate_name(mocker):
+
+    def _update(service_id,
+                service_name,
+                active,
+                limit,
+                restricted,
+                users):
+        json_mock = Mock(return_value={'message': {'name': ["Duplicate service name '{}'".format(service_name)]}})
+        resp_mock = Mock(status_code=400, json=json_mock)
+        http_error = HTTPError(response=resp_mock, message="Default message")
+        raise http_error
+
+    return mocker.patch(
+        'app.notifications_api_client.update_service', side_effect=_update)
+
+
 SERVICE_ONE_ID = "596364a0-858e-42c8-9062-a8fe822260eb"
 SERVICE_TWO_ID = "147ad62a-2951-4fa1-9ca0-093cd1a52c52"