api: fix revisions resolving

 *Fixes revisions resolving when there are gaps in revisions numbers

*INSPIR-3486

invenio_records/api.py

@@ -16,6 +16,7 @@
 from invenio_db import db
 from jsonpatch import apply_patch
 from sqlalchemy.orm.attributes import flag_modified
+from sqlalchemy.orm.exc import NoResultFound
 from werkzeug.local import LocalProxy
 
 from .errors import MissingModelError
@@ -398,8 +399,20 @@ def __next__(self):
         return RecordRevision(next(self._it))
 
     def __getitem__(self, revision_id):
-        """Get a specific revision."""
-        return RecordRevision(self.model.versions[revision_id])
+        """Get a specific revision.
+
+        Revision id is always smaller by 1 from version_id.
+        """
+        if revision_id < 0:
+            return RecordRevision(self.model.versions[revision_id])
+        try:
+            return RecordRevision(
+                self.model.versions.filter_by(
+                    version_id=revision_id + 1
+                ).one()
+            )
+        except NoResultFound:
+            raise IndexError
 
     def __contains__(self, revision_id):
         """Test if revision exists."""

tests/test_api.py

@@ -182,6 +182,46 @@ def test_revisions(app, db):
     assert 5 not in record.revisions
 
 
+def test_retrieve_proper_revision(app, db):
+    """Check accessing revision with gaps
+
+    Test checks if it's possible to access proper revision
+    when revision numbers have 'gaps'
+    """
+    record = Record.create({'title': 'test 1'})
+    db.session.commit()
+    record['title'] = "test 2"
+    record.commit()
+    record['title'] = "test 3"
+    record.commit()
+    db.session.commit()
+    record['title'] = "test 4"
+    record.commit()
+    db.session.commit()
+    record['title'] = "test 5"
+    record.commit()
+    db.session.commit()
+
+    assert len(record.revisions) == 4
+    revs = list(record.revisions)
+    assert revs[0]['title'] == "test 1"
+    assert revs[0].revision_id == 0
+    assert revs[1]['title'] == "test 3"
+    assert revs[1].revision_id == 2
+    assert revs[2]['title'] == "test 4"
+    assert revs[2].revision_id == 3
+    assert revs[3]['title'] == "test 5"
+    assert revs[3].revision_id == 4
+
+    # Access revision by revision_id
+    rev_2 = record.revisions[2]
+    assert rev_2['title'] == "test 3"
+    assert rev_2.revision_id == 2
+
+    # Access revision by negative list index
+    assert rev_2 == record.revisions[-3]
+
+
 def test_record_update_mutable(app, db):
     """Test updating mutables in a record."""
     recid = uuid.UUID('262d2748-ba41-456f-a844-4d043a419a6f')