Bank transfer: Allow using external IDs for deduplication (#3803)

* Bank transfer: Allow using external IDs for deduplication

* Do not use empty string in nullable field

src/pretix/plugins/banktransfer/api.py

@@ -46,7 +46,7 @@ class BankTransactionSerializer(serializers.ModelSerializer):
     class Meta:
         model = BankTransaction
         fields = ('state', 'message', 'checksum', 'payer', 'reference', 'amount', 'date', 'order',
-                  'comment', 'iban', 'bic', 'currency')
+                  'comment', 'iban', 'bic', 'currency', 'external_id')
 
 
 class BankImportJobSerializer(serializers.ModelSerializer):

src/pretix/plugins/banktransfer/migrations/0011_banktransaction_external_id.py

@@ -0,0 +1,17 @@
+# Generated by Django 4.2.9 on 2024-01-09 09:30
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("banktransfer", "0010_bigint"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="banktransaction",
+            name="external_id",
+            field=models.CharField(db_index=True, max_length=190, null=True),
+        ),
+    ]

src/pretix/plugins/banktransfer/models.py

@@ -82,6 +82,7 @@ class BankTransaction(models.Model):
     currency = models.CharField(max_length=10, null=True)
     state = models.CharField(max_length=32, choices=STATES, default=STATE_UNCHECKED)
     message = models.TextField()
+    external_id = models.CharField(max_length=190, db_index=True, null=True, blank=True)
     checksum = models.CharField(max_length=190, db_index=True)
     payer = models.TextField(blank=True)
     reference = models.TextField(blank=True)

src/pretix/plugins/banktransfer/tasks.py

@@ -307,6 +307,9 @@ def _get_unknown_transactions(job: BankImportJob, data: list, event: Event = Non
     known_checksums = set(t['checksum'] for t in BankTransaction.objects.filter(
         Q(event=event) if event else Q(organizer=organizer)
     ).values('checksum'))
+    known_by_external_id = set((t['external_id'], t['date'], t['amount']) for t in BankTransaction.objects.filter(
+        Q(event=event) if event else Q(organizer=organizer), external_id__isnull=False
+    ).values('external_id', 'date', 'amount'))
 
     transactions = []
     for row in data:
@@ -328,14 +331,17 @@ def _get_unknown_transactions(job: BankImportJob, data: list, event: Event = Non
         trans = BankTransaction(event=event, organizer=organizer, import_job=job,
                                 payer=row.get('payer', ''),
                                 reference=row.get('reference', ''),
-                                amount=amount, date=row.get('date', ''),
-                                iban=row.get('iban', ''), bic=row.get('bic', ''),
+                                amount=amount,
+                                date=row.get('date', ''),
+                                iban=row.get('iban', ''),
+                                bic=row.get('bic', ''),
+                                external_id=row.get('external_id'),
                                 currency=event.currency if event else job.currency)
 
         trans.date_parsed = parse_date(trans.date)
 
         trans.checksum = trans.calculate_checksum()
-        if trans.checksum not in known_checksums:
+        if trans.checksum not in known_checksums and (not trans.external_id or (trans.external_id, trans.date, trans.amount) not in known_by_external_id):
             trans.state = BankTransaction.STATE_UNCHECKED
             trans.save()
             transactions.append(trans)