Inconsistent handling of CriteriaBuilder.literal() depending on context

I have the following code snippet:

CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<String> q = cb.createQuery(String.class);
Root<JPABook> from = q.from(JPABook.class);
q.select(cb.<String>selectCase()
           .when(cb.equal(from.get("title"), cb.literal("Animal Farm")), cb.literal("Animal Farm"))
           .otherwise(cb.nullLiteral(String.class)));
em.createQuery(q).getResultList();

It generates this SQL string:

select case when jpabook0_.title=? then 'Animal Farm' else cast(null as varchar(255)) end as col_0_0_ from t_book jpabook0_

As you can see, the literal in the CASE expression's predicate is sent to the server as a bind variable, whereas the literal in the THEN clause is sent as a literal.

I personally believe that the latter is correct because the intention of using CriteriaBuilder.literal() is for an actual literal to make it into the generated SQL string. Because if users wanted a parameter, they could have used CriteriaBuilder.parameter() instead. What's the point of literal() if it still generates a parameter.

I've already had this discussion with Vlad Mihalcea on Twitter:
https://twitter.com/lukaseder/status/869209243282530304

Even if you might not agree with the above, I think the behaviour of all CriteriaBuilder.literal() calls should be consistent, so:

• Either generate only actual literals in generated SQL (properly escaping them of course!)
• Or generate only bind variables in generated SQL

Side-note: try using a Java string containing an apostrophe instead in both places: "This isn't working" and see what happens...

Related issue: https://hibernate.atlassian.net/browse/HHH-9576