Incidents: add `download_file` helper & tests

Co-authored-by: MarkKoz <[email protected]>

2 files changed, 33 insertions, 0 deletions

diff --git a/bot/cogs/moderation/incidents.py b/bot/cogs/moderation/incidents.py
index be46c8202..65b0e458e 100644
--- a/bot/cogs/moderation/incidents.py
+++ b/bot/cogs/moderation/incidents.py
@@ -42,6 +42,19 @@ ALLOWED_ROLES: t.Set[int] = set(Guild.moderation_roles)
 ALL_SIGNALS: t.Set[str] = {signal.value for signal in Signal}
 
 
+async def download_file(attachment: discord.Attachment) -> t.Optional[discord.File]:
+    """
+    Download & return `attachment` file.
+
+    If the download fails, the reason is logged and None will be returned.
+    """
+    log.debug(f"Attempting to download attachment: {attachment.filename}")
+    try:
+        return await attachment.to_file()
+    except Exception:
+        log.exception("Failed to download attachment")
+
+
 def make_embed(incident: discord.Message, outcome: Signal, actioned_by: discord.Member) -> discord.Embed:
     """
     Create an embed representation of `incident` for the #incidents-archive channel.
diff --git a/tests/bot/cogs/moderation/test_incidents.py b/tests/bot/cogs/moderation/test_incidents.py
index 789a37cd4..273916199 100644
--- a/tests/bot/cogs/moderation/test_incidents.py
+++ b/tests/bot/cogs/moderation/test_incidents.py
@@ -12,6 +12,7 @@ from bot.cogs.moderation import Incidents, incidents
 from bot.constants import Colours
 from tests.helpers import (
     MockAsyncWebhook,
+    MockAttachment,
     MockBot,
     MockMember,
     MockMessage,
@@ -69,6 +70,25 @@ mock_404 = discord.NotFound(
 )
 
 
+class TestDownloadFile(unittest.IsolatedAsyncioTestCase):
+    """Collection of tests for the `download_file` helper function."""
+
+    async def test_download_file_success(self):
+        """If `to_file` succeeds, function returns the acquired `discord.File`."""
+        file = MagicMock(discord.File, filename="bigbadlemon.jpg")
+        attachment = MockAttachment(to_file=AsyncMock(return_value=file))
+
+        acquired_file = await incidents.download_file(attachment)
+        self.assertIs(file, acquired_file)
+
+    async def test_download_file_fail(self):
+        """If `to_file` fails, function handles the exception & returns None."""
+        attachment = MockAttachment(to_file=AsyncMock(side_effect=mock_404))
+
+        acquired_file = await incidents.download_file(attachment)
+        self.assertIsNone(acquired_file)
+
+
 class TestMakeEmbed(unittest.TestCase):
     """Collection of tests for the `make_embed` helper function."""