When exporting VDB with a UDF, the resulting DDL contains the RETURN parameter in the parameters list. According to the Teiid docs, the return parameter should not be specified.

Generated DDL:

CREATE VIRTUAL FUNCTION concatNull (stringLeft string(4000), stringRight string(4000), result string(4000)) RETURNS string

) OPTIONS("FUNCTION-CATEGORY" 'MY_TESTING_FUNCTION_CATEGORY', JAVA_CLASS 'userdefinedfunctions.MyConcatNull', JAVA_METHOD 'myConcatNull')

Expected DDL:

CREATE VIRTUAL FUNCTION concatNull (stringLeft string(4000), stringRight string(4000)) RETURNS string

 OPTIONS("FUNCTION-CATEGORY" 'MY_TESTING_FUNCTION_CATEGORY', JAVA_CLASS 'userdefinedfunctions.MyConcatNull', JAVA_METHOD 'myConcatNull')

(note that the generated DDL also contains an unrelated syntax error due to TEIIDDES-2697)