fix: set upstream link for re-copied block from course originally from library (#35784)

Sets upstream link to library block for blocks that were copied from a course block which were originally copied/imported from a library.

Author: navinkarkera

cms/djangoapps/contentstore/helpers.py

@@ -24,7 +24,7 @@
 from xmodule.xml_block import XmlMixin
 
 from cms.djangoapps.models.settings.course_grading import CourseGradingModel
-from cms.lib.xblock.upstream_sync import UpstreamLink, BadUpstream, BadDownstream, fetch_customizable_fields
+from cms.lib.xblock.upstream_sync import UpstreamLink, UpstreamLinkException, fetch_customizable_fields
 from openedx.core.djangoapps.site_configuration import helpers as configuration_helpers
 import openedx.core.djangoapps.content_staging.api as content_staging_api
 import openedx.core.djangoapps.content_tagging.api as content_tagging_api
@@ -323,6 +323,56 @@ def import_staged_content_from_user_clipboard(parent_key: UsageKey, request) ->
     return new_xblock, notices
 
 
+def _fetch_and_set_upstream_link(
+    copied_from_block: str,
+    copied_from_version_num: int,
+    temp_xblock: XBlock,
+    user: User
+):
+    """
+    Fetch and set upstream link for the given xblock. This function handles following cases:
+    * the xblock is copied from a v2 library; the library block is set as upstream.
+    * the xblock is copied from a course; no upstream is set, only copied_from_block is set.
+    * the xblock is copied from a course where the source block was imported from a library; the original libary block
+      is set as upstream.
+    """
+    # Try to link the pasted block (downstream) to the copied block (upstream).
+    temp_xblock.upstream = copied_from_block
+    try:
+        UpstreamLink.get_for_block(temp_xblock)
+    except UpstreamLinkException:
+        # Usually this will fail. For example, if the copied block is a modulestore course block, it can't be an
+        # upstream. That's fine! Instead, we store a reference to where this block was copied from, in the
+        # 'copied_from_block' field (from AuthoringMixin).
+
+        # In case if the source block was imported from a library, we need to check its upstream
+        # and set the same upstream link for the new block.
+        source_descriptor = modulestore().get_item(UsageKey.from_string(copied_from_block))
+        if source_descriptor.upstream:
+            _fetch_and_set_upstream_link(
+                source_descriptor.upstream,
+                source_descriptor.upstream_version,
+                temp_xblock,
+                user,
+            )
+        else:
+            # else we store a reference to where this block was copied from, in the 'copied_from_block'
+            # field (from AuthoringMixin).
+            temp_xblock.upstream = None
+            temp_xblock.copied_from_block = copied_from_block
+    else:
+        # But if it doesn't fail, then populate the `upstream_version` field based on what was copied. Note that
+        # this could be the latest published version, or it could be an an even newer draft version.
+        temp_xblock.upstream_version = copied_from_version_num
+        # Also, fetch upstream values (`upstream_display_name`, etc.).
+        # Recall that the copied block could be a draft. So, rather than fetching from the published upstream (which
+        # could be older), fetch from the copied block itself. That way, if an author customizes a field, but then
+        # later wants to restore it, it will restore to the value that the field had when the block was pasted. Of
+        # course, if the author later syncs updates from a *future* published upstream version, then that will fetch
+        # new values from the published upstream content.
+        fetch_customizable_fields(upstream=temp_xblock, downstream=temp_xblock, user=user)
+
+
 def _import_xml_node_to_parent(
     node,
     parent_xblock: XBlock,
@@ -404,28 +454,7 @@ def _import_xml_node_to_parent(
         raise NotImplementedError("We don't yet support pasting XBlocks with children")
     temp_xblock.parent = parent_key
     if copied_from_block:
-        # Try to link the pasted block (downstream) to the copied block (upstream).
-        temp_xblock.upstream = copied_from_block
-        try:
-            UpstreamLink.get_for_block(temp_xblock)
-        except (BadDownstream, BadUpstream):
-            # Usually this will fail. For example, if the copied block is a modulestore course block, it can't be an
-            # upstream. That's fine! Instead, we store a reference to where this block was copied from, in the
-            # 'copied_from_block' field (from AuthoringMixin).
-            temp_xblock.upstream = None
-            temp_xblock.copied_from_block = copied_from_block
-        else:
-            # But if it doesn't fail, then populate the `upstream_version` field based on what was copied. Note that
-            # this could be the latest published version, or it could be an an even newer draft version.
-            temp_xblock.upstream_version = copied_from_version_num
-            # Also, fetch upstream values (`upstream_display_name`, etc.).
-            # Recall that the copied block could be a draft. So, rather than fetching from the published upstream (which
-            # could be older), fetch from the copied block itself. That way, if an author customizes a field, but then
-            # later wants to restore it, it will restore to the value that the field had when the block was pasted. Of
-            # course, if the author later syncs updates from a *future* published upstream version, then that will fetch
-            # new values from the published upstream content.
-            fetch_customizable_fields(upstream=temp_xblock, downstream=temp_xblock, user=user)
-
+        _fetch_and_set_upstream_link(copied_from_block, copied_from_version_num, temp_xblock, user)
     # Save the XBlock into modulestore. We need to save the block and its parent for this to work:
     new_xblock = store.update_item(temp_xblock, user.id, allow_not_found=True)
     parent_xblock.children.append(new_xblock.location)
@@ -436,7 +465,7 @@ def _import_xml_node_to_parent(
         # Allow an XBlock to do anything fancy it may need to when pasted from the clipboard.
         # These blocks may handle their own children or parenting if needed. Let them return booleans to
         # let us know if we need to handle these or not.
-        children_handed = new_xblock.studio_post_paste(store, node)
+        children_handled = new_xblock.studio_post_paste(store, node)
 
     if not children_handled:
         for child_node in child_nodes:

cms/djangoapps/contentstore/views/tests/test_clipboard_paste.py

@@ -455,26 +455,6 @@ def setUp(self):
         self.lib_block_tags = ['tag_1', 'tag_5']
         tagging_api.tag_object(str(self.lib_block_key), taxonomy_all_org, self.lib_block_tags)
 
-    def test_paste_from_library_creates_link(self):
-        """
-        When we copy a v2 lib block into a course, the dest block should be linked up to the lib block.
-        """
-        copy_response = self.client.post(CLIPBOARD_ENDPOINT, {"usage_key": str(self.lib_block_key)}, format="json")
-        assert copy_response.status_code == 200
-
-        paste_response = self.client.post(XBLOCK_ENDPOINT, {
-            "parent_locator": str(self.course.usage_key),
-            "staged_content": "clipboard",
-        }, format="json")
-        assert paste_response.status_code == 200
-
-        new_block_key = UsageKey.from_string(paste_response.json()["locator"])
-        new_block = modulestore().get_item(new_block_key)
-        assert new_block.upstream == str(self.lib_block_key)
-        assert new_block.upstream_version == 3
-        assert new_block.upstream_display_name == "MCQ-draft"
-        assert new_block.upstream_max_attempts == 5
-
     def test_paste_from_library_read_only_tags(self):
         """
         When we copy a v2 lib block into a course, the dest block should have read-only copied tags.
@@ -555,6 +535,34 @@ def test_paste_from_library_copies_asset(self):
         assert image_asset.name == "1px.webp"
         assert image_asset.length == len(webp_raw_data)
 
+    def test_paste_from_course_block_imported_from_library_creates_link(self):
+        """
+        When we copy a course xblock which was imported or copied from v2 lib block into a course,
+        the dest block should be linked up to the original lib block.
+        """
+        def _copy_paste_and_assert_link(key_to_copy):
+            copy_response = self.client.post(CLIPBOARD_ENDPOINT, {"usage_key": str(key_to_copy)}, format="json")
+            assert copy_response.status_code == 200
+
+            paste_response = self.client.post(XBLOCK_ENDPOINT, {
+                "parent_locator": str(self.course.usage_key),
+                "staged_content": "clipboard",
+            }, format="json")
+            assert paste_response.status_code == 200
+
+            new_block_key = UsageKey.from_string(paste_response.json()["locator"])
+            new_block = modulestore().get_item(new_block_key)
+            assert new_block.upstream == str(self.lib_block_key)
+            assert new_block.upstream_version == 3
+            assert new_block.upstream_display_name == "MCQ-draft"
+            assert new_block.upstream_max_attempts == 5
+            return new_block_key
+
+        # first verify link for copied block from library
+        new_block_key = _copy_paste_and_assert_link(self.lib_block_key)
+        # next verify link for copied block from the pasted block
+        _copy_paste_and_assert_link(new_block_key)
+
 
 class ClipboardPasteFromV1LibraryTestCase(ModuleStoreTestCase):
     """