fix: snapshot channel fields on draft ChannelVersion in save()

Loosen the snapshot condition in ChannelVersion.save() to also fire when
version is None (draft rows), so every draft publish captures the current
channel name, description, thumbnail encoding, tagline, and language on
the draft ChannelVersion. Repeated draft publishes always reflect the
latest channel state.

Tests cover: first draft publish populates all four snapshot fields, and a
second draft publish after mutating channel metadata (including language
change from "en" to "fr") refreshes all four fields on the existing row.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: rtibblesbot

contentcuration/contentcuration/models.py

@@ -1671,9 +1671,12 @@ def save(self, *args, **kwargs):
         if self.version is not None and self.version > self.channel.version:
             raise ValidationError("Version cannot be greater than channel version")
 
-        if self._state.adding and self.version == self.channel.version:
-            # When creating a new ChannelVersion for current channel version,
-            # snapshot the current channel info
+        if self.version is None or (
+            self._state.adding and self.version == self.channel.version
+        ):
+            # Snapshot channel info when creating a versioned ChannelVersion for the
+            # current channel version, or on every save for draft (version=None) rows
+            # so that repeated draft publishes always reflect the latest channel state.
             self.channel_name = self.channel.name
             self.channel_description = self.channel.description
             self.channel_tagline = self.channel.tagline

contentcuration/contentcuration/tests/utils/test_publish.py

@@ -379,3 +379,63 @@ def test_special_permissions_distributable_false_for_draft_publish(self):
                 license_obj.distributable,
                 "distributable must stay False for draft publishes",
             )
+
+    def test_draft_publish_populates_channel_snapshot_fields(self):
+        """
+        After the first draft publish, channel_name, channel_description,
+        channel_thumbnail_encoding, and channel_language on the draft
+        ChannelVersion reflect the channel's state at publish time.
+        """
+        self.channel.name = "Snapshot Channel"
+        self.channel.description = "Snapshot description"
+        self.channel.thumbnail_encoding = {"base64": "abc123"}
+        self.channel.save()
+
+        self._run_draft_publish()
+        draft_version = self._get_draft_version()
+
+        self.assertEqual(draft_version.channel_name, "Snapshot Channel")
+        self.assertEqual(draft_version.channel_description, "Snapshot description")
+        self.assertEqual(draft_version.channel_thumbnail_encoding, {"base64": "abc123"})
+        self.assertEqual(draft_version.channel_language_id, self.channel.language_id)
+
+    def test_second_draft_publish_refreshes_channel_snapshot_fields(self):
+        """
+        A second draft publish after mutating channel metadata must overwrite
+        the stale snapshot values on the existing draft ChannelVersion row —
+        for all four snapshot fields.
+
+        channel.language is changed from "en" to "fr" to confirm the refresh
+        is not vacuous (the language snapshot must change to the new value).
+        """
+        self.channel.name = "Old Name"
+        self.channel.description = "Old description"
+        self.channel.thumbnail_encoding = {"base64": "old_thumb"}
+        # language is already "en" from testdata.channel(); no need to set it
+        self.channel.save()
+
+        self._run_draft_publish()
+        draft_version = self._get_draft_version()
+
+        self.assertEqual(draft_version.channel_name, "Old Name")
+        self.assertEqual(
+            draft_version.channel_thumbnail_encoding, {"base64": "old_thumb"}
+        )
+        self.assertEqual(draft_version.channel_language_id, "en")
+
+        # Mutate all four fields; language changes from "en" to "fr"
+        self.channel.name = "New Name"
+        self.channel.description = "New description"
+        self.channel.thumbnail_encoding = {"base64": "new_thumb"}
+        self.channel.language_id = "fr"
+        self.channel.save()
+
+        self._run_draft_publish()
+        draft_version.refresh_from_db()
+
+        self.assertEqual(draft_version.channel_name, "New Name")
+        self.assertEqual(draft_version.channel_description, "New description")
+        self.assertEqual(
+            draft_version.channel_thumbnail_encoding, {"base64": "new_thumb"}
+        )
+        self.assertEqual(draft_version.channel_language_id, "fr")