[master < T1209] Fix API bug on accessing deleted object

[antoniofilipovic]

Issue: When doing detach delete on graph, and accessing deleted objects from C++ API, if you are accessing From and To vertex of deleted edge, error occurs that you are accessing deleted vertex although it shouldn't.

When a vertex is detach deleted, its VertexAccessor is marked for_deleted_, and out|in EdgeAccessors are marked for_deleted_. VertexAccessors which you can access from EdgeAccessor are not marked for_deleted_. This creates a slight problem when working with deleted objects in API, because only EdgeAccessor is marked for_deleted_ not also its VertexAccessors. Therefore some VertexAccessors have wrong information, marking for_deleted_ as false instead of true.

[master < Task] PR

• Check, and update documentation if necessary
• Provide the full content or a guide for the final git message

To keep docs changelog up to date, one more thing to do:

• Write a release note here, including added/changed clauses
• Tag someone from docs team in the comments

[antepusic]

Everything looks fine, but I’d prefer to extend FromVertex and ToVertex instead of creating new methods. The new ones’ names (FromVertexWithDeleted and ToVertexWithDeleted) really aren’t very clear, and tbh I can’t think of a name that’s both clear and descriptive.

Clarification: I recommend sth like this:

VertexAccessor EdgeAccessor::FromVertex(bool edge_for_deleted = false) const {
  if (UNLIKELY(edge_for_deleted)) {
    return VertexAccessor{from_vertex_, transaction_, indices_,
                          constraints_, config_,      for_deleted_ && from_vertex_->deleted};
  } 
  return VertexAccessor{from_vertex_, transaction_, indices_, constraints_, config_};
}

[vpavicic]

@antoniofilipovic - can you write me a release note (RN)?

[antoniofilipovic]

This PR enables to access deleted vertex from deleted edge when being processed as part of trigger function