[GROOVY-8096] setScriptBaseClass with Java base class breaks @Field initialization from Binding due to generated call to wrong constructor

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.4.8
• Fix Version/s: 5.0.0-alpha-2
• Component/s: Compiler, GroovyScriptEngine
• Labels: test
• Assignee: Eric Milles
• Reporter: Christoffer Hammarström
• Created: 22/Feb/17 02:21
• Updated: 15/Jan/24 15:40
• Resolved: 23/Aug/23 20:59

Description

I created a pull request on GitHub with a failing test showing the problem: https://github.com/apache/groovy/pull/502

This test fails because ModuleNode.createStatementsClass() calls .getSuperClass().getDeclaredConstructor(SCRIPT_CONTEXT_CTOR) and gets null back, though the constructor does exist!

ModuleNode.setScriptBaseClassFromConfig(ClassNode)
calls .setSuperClass(ClassHelper.make(baseClassName)) on the scriptDummy ClassNode.

The ClassNode created for this script's base class has .lazyInitDone = true and .constructors = null

ModuleNode.createStatementsClass() calls .getSuperClass().getDeclaredConstructor(SCRIPT_CONTEXT_CTOR)

Then ClassNode.constructors is set to an empty ArrayList in ClassNode.getDeclaredConstructors(), insteaf of looking them up from the Java class.

The script constructor is then generated in ModuleNode.createStatementsClass() as:
BROKEN BEHAVIOUR

     Constructor(Binding context) {
         super();             // Fields are initialized after the call to super()
                              // Fields are initialized here with new Binding() instead of context
         setBinding(context); // This is too late, fields are initialized after super(), before this call to setBinding
     }

instead of
EXPECTED BEHAVIOUR

     Constructor(Binding context) {
         super(context); // Fields are initialized after the call to super(context)
     }

We're calling the default constructor in the base class with super(), instead of passing along the Binding context with super(context)

This breaks initialization of Fields that depend on the Binding context, because Fields are initialized between the call to super() and the setBinding(context): http://stackoverflow.com/a/14806340/233014

This leads to MissingPropertyException because we're trying to look up variables from the new Binding() created in the default constructor, instead of the binding we passed in.

For convenience, here is the failing test:

GroovyShellTest2.groovy

    void testBindingsInFieldInitializersWithConfigJavaBaseScript() {
        def config = new org.codehaus.groovy.control.CompilerConfiguration()
        config.scriptBaseClass = BindingScript.class.name

        def shell = new GroovyShell(config);
        def scriptText = '''
        @groovy.transform.Field def script_args = getProperty('args')    // Will get MissingPropertyException here because this @Field is initialized after the call to super(), before the call to setBinding in the script constructor

        assert script_args[0] == 'Hello Groovy'
        script_args[0]
'''

        def arg0 = 'Hello Groovy'
        def result = shell.run scriptText, 'TestBindingsInFieldInitializersWithConfigJavaBaseScript.groovy', [arg0]
        assert result == arg0
    }

and the Java script base class:

BindingScript.java

package groovy.lang;

/**
 * A Script which requires a Binding passed in the constructor and disallows calling the default constructor.
 */
public abstract class BindingScript extends Script {
    // Making the default constructor private instead gives IllegalAccessError
    // Removing the default constructor instead gives NoSuchMethodError
    // Removing both constructors just calls to the default constructor in groovy.lang.Script giving MissingPropertyException on field initialization
    protected BindingScript() {
        // This constructor erroneously gets called instead of the other one
    }
    
    protected BindingScript(Binding binding) {
        super(binding);
        // This is the constructor that should have been called, because then the binding would have been passed in the above call, before @Fields are initialised.
    }
}

Issue Links

• relates to: GROOVY-11154 Script subclasses cannot have constructors with arguments
• links to: GitHub Pull Request #502
• links to: GitHub Pull Request #502