[GROOVY-8975] GroovyCastException on the result of CliBuilder.parseFromSpec

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.5.5
• Fix Version/s: 3.0.0-beta-1, 2.5.7
• Component/s: groovy-runtime
• Assignee: Paul King
• Reporter: Mauro Molinari
• Created: 30/Jan/19 12:01
• Updated: 20/May/19 07:31
• Resolved: 19/Feb/19 03:54

Description

I'm trying to follow the tutorial about the use of CliBuilder in Groovy with Groovy 2.5.5. Copying the code at Annotating methods of an interface paragraph, at runtime I have the following Exception:

Exception in thread "main" org.codehaus.groovy.runtime.typehandling.GroovyCastException: Cannot cast object '{help=groovy.cli.picocli.CliBuilder$_extractAttributesFromMethod_closure12@3bb9a3ff}' with class 'java.util.LinkedHashMap' to class 'mypackage.IHello' due to: groovy.lang.GroovyRuntimeException: Could not find matching constructor for: mypackage.IHello(LinkedHashMap)
        at org.codehaus.groovy.runtime.typehandling.DefaultTypeTransformation.continueCastOnSAM(DefaultTypeTransformation.java:412)
        at org.codehaus.groovy.runtime.typehandling.DefaultTypeTransformation.continueCastOnNumber(DefaultTypeTransformation.java:328)
        at org.codehaus.groovy.runtime.typehandling.DefaultTypeTransformation.castToType(DefaultTypeTransformation.java:242)
        at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.castToType(ScriptBytecodeAdapter.java:617)
        at mypackage.MyMain.main(MyMain.groovy:20)Exception in thread "main" org.codehaus.groovy.runtime.typehandling.GroovyCastException: Cannot cast object '{help=groovy.cli.picocli.CliBuilder$_extractAttributesFromMethod_closure12@3bb9a3ff}' with class 'java.util.LinkedHashMap' to class 'mypackage.IHello' due to: groovy.lang.GroovyRuntimeException: Could not find matching constructor for: mypackage.IHello(LinkedHashMap)
        at org.codehaus.groovy.runtime.typehandling.DefaultTypeTransformation.continueCastOnSAM(DefaultTypeTransformation.java:412)
        at org.codehaus.groovy.runtime.typehandling.DefaultTypeTransformation.continueCastOnNumber(DefaultTypeTransformation.java:328)
        at org.codehaus.groovy.runtime.typehandling.DefaultTypeTransformation.castToType(DefaultTypeTransformation.java:242)
        at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.castToType(ScriptBytecodeAdapter.java:617)
        at mypackage.MyMain.main(MyMain.groovy:20)

The exception occurs at this line:
IHello hello = cli.parseFromSpec(IHello, argz)

The exception goes away (and all works fine) if I replace it with:
def hello = cli.parseFromSpec(IHello, argz)

I tried to downgrade Groovy down to version 2.5.0 and I always get the exception. So this really puzzles me, since the mentioned tutorial is quite simple and straight to follow...