jamesfredley opened a new issue, #16712:
URL: https://github.com/apache/grails-core/issues/16712
## Summary
#16597 taught HQL projection analysis to ignore a `SELECT` nested inside
parentheses, so a real subquery is no longer stripped. The same depth check
treats parentheses around the root query as a subquery. A valid parenthesized
query, including one with no subquery, is then given the domain class as its
result type instead of the scalar type.
## What goes wrong
`HqlQueryContext.indexOfTopLevel()` increments depth on every `(`. For
`(select b.title from Book b)` the root `select` is therefore not visible.
`countHqlProjections()` returns 0, and `getTarget()` returns the domain class
(`Book`) rather than `Object`. `HibernateHqlQueryCreator` passes that class to
`session.createQuery()`, and a query that previously returned titles fails with
a result-type mismatch.
```groovy
Book.executeQuery("(select b.title from Book b)")
```
Before the merge, normalization left this query alone and projection
analysis returned `Object.class`. A fully parenthesized scalar `UNION` branch
has the same problem. Queries that are not wrapped in parentheses are
unaffected.
## Introduced by
- https://github.com/apache/grails-core/pull/16597
- Merge commit `85d7c8621c912513be9916a98a96224e0758f4b5` on `8.0.x`
-
`grails-data-hibernate7/core/src/main/groovy/org/grails/orm/hibernate/query/HqlQueryContext.java`
lines 313-317, with the bad target chosen at line 171
## Fix
Distinguish parentheses that wrap the root query from parentheses that wrap
a nested subquery. For a parenthesized root query, keep the original HQL and
let Hibernate infer the result type (the existing null target-class path)
instead of falling back to the domain class. Add a regression for `(select
b.title from Book b)` and for a parenthesized scalar union branch.
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