Make sure that migrations don't run twice

gratipay/models/team.py

@@ -51,6 +51,12 @@ def create_new(cls, owner, fields):
               owner.username))
 
     def migrate_tips(self):
+        subscriptions = self.db.all("SELECT * FROM subscriptions WHERE team=%s", (self.slug,))
+
+        # Make sure the migration hasn't been done already
+        if subscriptions:
+            raise AlreadyMigrated
+
         self.db.run("""
 
             INSERT INTO subscriptions
@@ -66,3 +72,4 @@ def migrate_tips(self):
 
         """, {'slug': self.slug, 'owner': self.owner})
 
+class AlreadyMigrated(Exception): pass

tests/py/test_teams.py

@@ -1,9 +1,11 @@
 from __future__ import unicode_literals
-from gratipay.models._mixin_team import StubParticipantAdded
 
+import pytest
+
+from gratipay.models._mixin_team import StubParticipantAdded
 from gratipay.testing import Harness
 from gratipay.security.user import User
-from gratipay.models.team import Team
+from gratipay.models.team import Team, AlreadyMigrated
 
 
 class TestNewTeams(Harness):
@@ -103,6 +105,23 @@ def test_migrate_tips_to_subscriptions(self):
         assert subscriptions[1].team == 'new_team'
         assert subscriptions[1].amount == 2
 
+    def test_migrate_tips_only_runs_once(self):
+        alice = self.make_participant('alice', claimed_time='now')
+        self.make_participant('old_team')
+        alice.set_tip_to('old_team', '1.00')
+        new_team = self.make_team('new_team', owner='old_team')
+
+        self.db.run("""
+            INSERT INTO subscriptions
+                        (ctime, subscriber, team, amount)
+                 VALUES (CURRENT_TIMESTAMP, 'alice', 'new_team', 1)
+        """)
+
+        with pytest.raises(AlreadyMigrated):
+            new_team.migrate_tips()
+
+        subscriptions = self.db.all("SELECT * FROM subscriptions")
+        assert len(subscriptions) == 1
 
 class TestOldTeams(Harness):