Add allowed_campaign_count field to Channel model and implement counter cache logic

twitch/tests/test_migrations.py

@@ -0,0 +1,86 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+import pytest
+from django.db import connection
+from django.db.migrations.executor import MigrationExecutor
+from django.db.migrations.state import StateApps
+
+if TYPE_CHECKING:
+    from django.db.migrations.state import StateApps
+
+    from twitch.models import Channel
+    from twitch.models import DropCampaign
+    from twitch.models import Game
+
+
+@pytest.mark.django_db(transaction=True)
+def test_0021_backfills_allowed_campaign_count() -> None:  # noqa: PLR0914
+    """Migration 0021 should backfill cached allowed campaign counts."""
+    migrate_from: list[tuple[str, str]] = [
+        ("twitch", "0020_rewardcampaign_tw_reward_ends_starts_idx"),
+    ]
+    migrate_to: list[tuple[str, str]] = [
+        ("twitch", "0021_channel_allowed_campaign_count_cache"),
+    ]
+
+    executor = MigrationExecutor(connection)
+    executor.migrate(migrate_from)
+    old_apps: StateApps = executor.loader.project_state(migrate_from).apps
+
+    Game: type[Game] = old_apps.get_model("twitch", "Game")
+    Channel: type[Channel] = old_apps.get_model("twitch", "Channel")
+    DropCampaign: type[DropCampaign] = old_apps.get_model("twitch", "DropCampaign")
+
+    game = Game.objects.create(
+        twitch_id="migration_backfill_game",
+        name="Migration Backfill Game",
+        display_name="Migration Backfill Game",
+    )
+    channel1 = Channel.objects.create(
+        twitch_id="migration_backfill_channel_1",
+        name="migrationbackfillchannel1",
+        display_name="Migration Backfill Channel 1",
+    )
+    channel2 = Channel.objects.create(
+        twitch_id="migration_backfill_channel_2",
+        name="migrationbackfillchannel2",
+        display_name="Migration Backfill Channel 2",
+    )
+    _channel3 = Channel.objects.create(
+        twitch_id="migration_backfill_channel_3",
+        name="migrationbackfillchannel3",
+        display_name="Migration Backfill Channel 3",
+    )
+    campaign1 = DropCampaign.objects.create(
+        twitch_id="migration_backfill_campaign_1",
+        name="Migration Backfill Campaign 1",
+        game=game,
+        operation_names=["DropCampaignDetails"],
+    )
+    campaign2 = DropCampaign.objects.create(
+        twitch_id="migration_backfill_campaign_2",
+        name="Migration Backfill Campaign 2",
+        game=game,
+        operation_names=["DropCampaignDetails"],
+    )
+
+    campaign1.allow_channels.add(channel1, channel2)
+    campaign2.allow_channels.add(channel1)
+
+    executor = MigrationExecutor(connection)
+    executor.migrate(migrate_to)
+    new_apps: StateApps = executor.loader.project_state(migrate_to).apps
+    new_channel: type[Channel] = new_apps.get_model("twitch", "Channel")
+
+    counts_by_twitch_id: dict[str, int] = {
+        channel.twitch_id: channel.allowed_campaign_count
+        for channel in new_channel.objects.order_by("twitch_id")
+    }
+
+    assert counts_by_twitch_id == {
+        "migration_backfill_channel_1": 2,
+        "migration_backfill_channel_2": 1,
+        "migration_backfill_channel_3": 0,
+    }