fix: crash in retrieving blockstore bundle links

If the bundle is deleted, `blockstore_cache.get_bundle_version_number(bundle_uuid)`
will raise an error.
Catch this error in `get_bundle_links`,
so the REST api doesn't crash with a 500 error when a linked bundle is deleted.

openedx/core/djangoapps/content_libraries/api.py

@@ -109,6 +109,7 @@ from openedx.core.lib.blockstore_api import (
     set_draft_link,
     commit_draft,
     delete_draft,
+    BundleNotFound,
 )
 from openedx.core.djangolib import blockstore_cache
 from openedx.core.djangolib.blockstore_cache import BundleCache
@@ -1003,12 +1004,15 @@ def get_bundle_links(library_key):
             opaque_key = libraries_linked[link_data.bundle_uuid].library_key
         except KeyError:
             opaque_key = None
-        # Append the link information:
+        try:
+            latest_version = blockstore_cache.get_bundle_version_number(link_data.bundle_uuid)
+        except BundleNotFound:
+            latest_version = 0
         results.append(LibraryBundleLink(
             id=link_name,
             bundle_uuid=link_data.bundle_uuid,
             version=link_data.version,
-            latest_version=blockstore_cache.get_bundle_version_number(link_data.bundle_uuid),
+            latest_version=latest_version,
             opaque_key=opaque_key,
         ))
     return results

openedx/core/djangoapps/content_libraries/tests/test_content_libraries.py

@@ -22,6 +22,7 @@ from openedx.core.djangoapps.content_libraries.tests.base import (
     URL_BLOCK_XBLOCK_HANDLER,
 )
 from openedx.core.djangoapps.content_libraries.constants import VIDEO, COMPLEX, PROBLEM, CC_4_BY, ALL_RIGHTS_RESERVED
+from openedx.core.djangolib.blockstore_cache import cache
 from common.djangoapps.student.tests.factories import UserFactory
 
 
@@ -745,6 +746,94 @@ class ContentLibrariesTest(ContentLibrariesRestApiTest):
         assert links_created[1]['latest_version'] == 2
         assert links_created[1]['opaque_key'] == bank_lib_id
 
+    def test_library_blocks_with_deleted_links(self):
+        """
+        Test that libraries can handle deleted links to bundles
+        """
+        # Create a problem bank:
+        bank_lib = self._create_library(slug="problem_bank1X", title="Problem Bank")
+        bank_lib_id = bank_lib["id"]
+        # Add problem1 to the problem bank:
+        p1 = self._add_block_to_library(bank_lib_id, "problem", "problem1X")
+        self._set_library_block_olx(p1["id"], """
+            <problem><multiplechoiceresponse>
+                    <p>What is an even number?</p>
+                    <choicegroup type="MultipleChoice">
+                        <choice correct="false">3</choice>
+                        <choice correct="true">2</choice>
+                    </choicegroup>
+            </multiplechoiceresponse></problem>
+        """)
+        # Commit the changes, creating version 1:
+        self._commit_library_changes(bank_lib_id)
+
+        # Create another problem bank:
+        bank_lib2 = self._create_library(slug="problem_bank2", title="Problem Bank 2")
+        bank_lib2_id = bank_lib2["id"]
+        # Add problem1 to the problem bank:
+        p2 = self._add_block_to_library(bank_lib2_id, "problem", "problem1X")
+        self._set_library_block_olx(p2["id"], """
+            <problem><multiplechoiceresponse>
+                    <p>What is an odd number?</p>
+                    <choicegroup type="MultipleChoice">
+                        <choice correct="true">3</choice>
+                        <choice correct="false">2</choice>
+                    </choicegroup>
+            </multiplechoiceresponse></problem>
+        """)
+        # Commit the changes, creating version 1:
+        self._commit_library_changes(bank_lib2_id)
+
+        lib = self._create_library(slug="problem_bank2X", title="Link Test Library")
+        lib_id = lib["id"]
+        # Link to the other libraries:
+        self._link_to_library(lib_id, "problem_bank", bank_lib_id)
+        self._link_to_library(lib_id, "problem_bank_v1", bank_lib2_id)
+
+        # check the API for retrieving links:
+        links_created = self._get_library_links(lib_id)
+        links_created.sort(key=lambda link: link["id"])
+        assert len(links_created) == 2
+
+        assert links_created[0]['id'] == 'problem_bank'
+        assert links_created[0]['bundle_uuid'] == bank_lib['bundle_uuid']
+        assert links_created[0]['version'] == 1
+        assert links_created[0]['latest_version'] == 1
+        assert links_created[0]['opaque_key'] == bank_lib_id
+
+        assert links_created[1]['id'] == 'problem_bank_v1'
+        assert links_created[1]['bundle_uuid'] == bank_lib2['bundle_uuid']
+        assert links_created[1]['version'] == 1
+        assert links_created[1]['latest_version'] == 1
+        assert links_created[1]['opaque_key'] == bank_lib2_id
+
+        # Delete one of the linked bundles/libraries
+        self._delete_library(bank_lib2_id)
+
+        # update the cache so we're not getting cached links in the next step
+        cache_key = 'bundle_version:{}:'.format(bank_lib['bundle_uuid'])
+        cache.delete(cache_key)
+        cache_key = 'bundle_version:{}:'.format(bank_lib2['bundle_uuid'])
+        cache.delete(cache_key)
+
+        links_created = self._get_library_links(lib_id)
+        links_created.sort(key=lambda link: link["id"])
+        assert len(links_created) == 2
+
+        assert links_created[0]['id'] == 'problem_bank'
+        assert links_created[0]['bundle_uuid'] == bank_lib['bundle_uuid']
+        assert links_created[0]['version'] == 1
+        assert links_created[0]['latest_version'] == 1
+        assert links_created[0]['opaque_key'] == bank_lib_id
+
+        # If a link has been deleted, the latest version will be 0,
+        # and the opaque key will be `None`.
+        assert links_created[1]['id'] == 'problem_bank_v1'
+        assert links_created[1]['bundle_uuid'] == bank_lib2['bundle_uuid']
+        assert links_created[1]['version'] == 1
+        assert links_created[1]['latest_version'] == 0
+        assert links_created[1]['opaque_key'] is None
+
     def test_library_blocks_limit(self):
         """
         Test that libraries don't allow more than specified blocks