null value support for dynamic finders

[demon101]

#1182

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[graemerocher]

Note that this fixed actually doesn't work downstream with Hibernate. I have disabled the tests that fail for the new test that was introduced until that can be investigated grails/grails-data-hibernate5@671413c

[graemerocher]

The test also fails in GORM for Neo4j

[demon101]

@graemerocher where I can find tests logs? Is it problem of test or code?

[graemerocher]

likely a problem with how the query is translated into the target query for each underlying implementation. The builds are run via Travis, but the logs won't tell you much other than NullValueEqualSpec you would need to run the tests for the underlying implementations (gorm-hibernate5 and gorm-neo4j)

[demon101]

@graemerocher strange, I have tested on app with 6.1 snapshot version (hibernate 5), everything works as expected, also NotEqual. Looks like problem in tests

[zyro23]

i think the problem is again that NULL in sql is never equals meaning that:

TestEntity.countByAgeNotEqual(11) == 2

fails because WHERE age <> 11 does not match the rows with age = NULL.

to make the test pass, the semantics/implementation of the NotEqual dynamic finder would have to be changed to match NotEqualOrIsNull for non-null values, i guess?
that of course may break existing application code, but this pull request already translates Equal(null) to IsNull (for all datastores) which both have a different meaning and different expected results in sql, too.