feat: added get/set_draft_version to publishing API

openedx_learning/core/publishing/api.py

@@ -180,11 +180,40 @@ def publish_from_drafts(
     return publish_log
 
 
-def delete_drafts(
-    learning_package_id: int,
-    draft_qset: QuerySet,
-):
-    pass
+def get_draft_version(publishable_entity_id: int) -> PublishableEntityVersion | None:
+    """
+    Return current draft PublishableEntityVersion for this PublishableEntity.
+
+    This function will return None if there is no current draft.
+    """
+    try:
+        draft = Draft.objects.select_related("version").get(
+            entity_id=publishable_entity_id
+        )
+    except Draft.DoesNotExist:
+        # No draft was ever created.
+        return None
+
+    # draft.version could be None if it was set that way by set_draft_version.
+    # Setting the Draft.version to None is how we show that we've "deleted" the
+    # content in Studio. 
+    return draft.version
+
+
+def set_draft_version(publishable_entity_id: int, publishable_entity_version_pk: int | None) -> None:
+    """
+    Modify the Draft of a PublishableEntity to be a PublishableEntityVersion.
+
+    This would most commonly be used to set the Draft to point to a newly
+    created PublishableEntityVersion that was created in Studio (because someone
+    edited some content). Setting a Draft's version to None is like deleting it
+    from Studio's editing point of view. We don't actually delete the Draft row
+    because we'll need that for publishing purposes (i.e. to delete content from
+    the published branch).
+    """
+    draft = Draft.objects.get(entity_id=publishable_entity_id)
+    draft.version_id = publishable_entity_version_pk
+    draft.save()
 
 
 def register_content_models(

tests/openedx_learning/core/publishing/test_api.py

@@ -8,8 +8,8 @@
 from django.core.exceptions import ValidationError
 from django.test import TestCase
 
-from openedx_learning.core.publishing.api import create_learning_package
-
+from openedx_learning.core.publishing import api as publishing_api
+from openedx_learning.core.publishing.models import Draft
 
 class CreateLearningPackageTestCase(TestCase):
     """
@@ -22,7 +22,7 @@ def test_normal(self) -> None:  # Note: we must specify '-> None' to opt in to t
         key = "my_key"
         title = "My Excellent Title with Emoji 🔥"
         created = datetime(2023, 4, 2, 15, 9, 0, tzinfo=timezone.utc)
-        package = create_learning_package(key, title, created)
+        package = publishing_api.create_learning_package(key, title, created)
 
         assert package.key == "my_key"
         assert package.title == "My Excellent Title with Emoji 🔥"
@@ -41,7 +41,7 @@ def test_auto_datetime(self) -> None:
         """
         key = "my_key"
         title = "My Excellent Title with Emoji 🔥"
-        package = create_learning_package(key, title)
+        package = publishing_api.create_learning_package(key, title)
 
         assert package.key == "my_key"
         assert package.title == "My Excellent Title with Emoji 🔥"
@@ -62,7 +62,7 @@ def test_non_utc_time(self) -> None:
         Require UTC timezone for created.
         """
         with pytest.raises(ValidationError) as excinfo:
-            create_learning_package("my_key", "A Title", datetime(2023, 4, 2))
+            publishing_api.create_learning_package("my_key", "A Title", datetime(2023, 4, 2))
         message_dict = excinfo.value.message_dict
 
         # Both datetime fields should be marked as invalid
@@ -73,8 +73,46 @@ def test_already_exists(self) -> None:
         """
         Raises ValidationError for duplicate keys.
         """
-        create_learning_package("my_key", "Original")
+        publishing_api.create_learning_package("my_key", "Original")
         with pytest.raises(ValidationError) as excinfo:
-            create_learning_package("my_key", "Duplicate")
+            publishing_api.create_learning_package("my_key", "Duplicate")
         message_dict = excinfo.value.message_dict
         assert "key" in message_dict
+
+
+class DraftTestCase(TestCase):
+
+    def test_draft_lifecycle(self):
+        """
+        Test basic lifecycle of a Draft.
+        """
+        created = datetime(2023, 4, 2, 15, 9, 0, tzinfo=timezone.utc)
+        package = publishing_api.create_learning_package(
+            "my_package_key",
+            "Draft Testing LearningPackage 🔥",
+            created=created,
+        )
+        entity = publishing_api.create_publishable_entity(
+            package.id,
+            "my_entity",
+            created,
+            created_by=None,
+        )
+        # Drafts are NOT created when a PublishableEntity is created, only when
+        # its first PublisahbleEntityVersion is.
+        assert publishing_api.get_draft_version(entity.id) is None
+
+        entity_version = publishing_api.create_publishable_entity_version(
+            entity_id=entity.id,
+            version_num=1,
+            title="An Entity 🌴",
+            created=created,
+            created_by=None,
+        )
+        assert entity_version == publishing_api.get_draft_version(entity.id)
+
+        # We never really remove rows from the table holding Drafts. We just
+        # mark the version as None.
+        publishing_api.set_draft_version(entity.id, None)
+        entity_version = publishing_api.get_draft_version(entity.id)
+        assert entity_version is None