Test UDF functions are revealed

[MichaelDrogalis]

When I run describe functions, I get test UDFs like TEST_UDF and COMPLEXFUNCTION. These shouldn't be visible.

[stevenpyzhang]

This is caused by #2804 . Will close this issue for now and hold off on doing any further work until there's further discussion for the other issue. There are some quick solutions that can address this, but it doesn't make sense to do them if resolving #2804 will fix this bug anyways.

I verified between the 5.2.x and 5.3.x branch that the functions only show up in the 5.3.x branch, which is when ksql-functional-tests were added. In total there are 6 functions that began showing up:

COMPLEXFUNCTION
CONFIGURABLEUDF
E2ECONFIGURABLEUDF
SOMEFUNCTION
TEST_UDAF
TEST_UDF

The reason why they show up is that in UdfLoader.java at line 140, fastClasspathScanner scans all jar files in the directory that contain "ksql-engine" in the path name so that it can find public internal UDF and UDAF to add to the functionRegistry. In ksql-functional-tests, there's a copy of the ksql-engine test-jar (contains the test UDF/UDAF) since that's a dependency for the functional tests. The scanner picks up on the test-jar, which results in the test functions being added to the function registry.

ksql-engine-5.4.0-SNAPSHOT-tests.jar

[big-andy-coates]

Closing as duplicate of #2804