nickl-
commented
1 year ago Related to late binding but slightly more complicated.
At #335 we discovered a valid java class definition which BeanShell cannot generate.
public abstract class MyParent {
public static final MyParent INSTANCE = new MyClass();
public abstract int getValue(Number number);
private static class MyClass extends MyParent {
public int getValue(Number number) {
return 1;
}
}
}// Error: Evaluation Error: Class: MyParent not found in namespace : at Line: 9 : in file: <unknown file> : MyParentA chicken or egg problem, members of the class definition references itself, and an inner class extends its parent. In this case the class itself is missing and required and cannot be made available later (late binding).
However this can be accomplished if we first create only the empty class and then recreate the class with its cyclic redundancy.
BeanShell 3.0.0-SNAPSHOT.3578
public abstract class MyParent {}
--> $0 = class MyParent :Class
public abstract class MyParent {
public static final MyParent INSTANCE = new MyClass();
public abstract int getValue(Number number);
private static class MyClass extends MyParent {
public int getValue(Number number) {
return 1;
}
}
}
--> $1 = class MyParent :ClassHowever because of the lack of late binding support we cannot do it the other way around because BeanShell will refuse any further mention of the problem class if an exception occurred.
After the first example trying to redefine the empty class results in the following error:
public abstract class MyParent {}
// Error: Internal Error: Defining class problem: MyParent: BeanShell cannot yet simultaneously define two or more dependent classes of the same name. Attempt to define: MyParent while defining: MyParent
EDIT: Turned this into a discussion and parent task, as it turns out there are multiple defects, with class generation. To manage these the parent task will group the separated issues.
Original post titled: Late binding on class generation now #696
Currently BeanShell requires bindings, like parent classes, to be in place already when classes are declared (and generated). This should not be a terminating exception, only at instantiation would binding be required, if we can defer the generation until then late binding for class generation will be accomplished.
As an example this is how jshell deals with it:
As we can see, even though it claims that class A was created, it was not. Only once the dependencies were available could the class be generated and made accessible.
While solving the issues with
superI also discovered that parent classes are instantiated in order to generate (or instantiate need to make sure) a child class. Perhaps this is required but would be preferable to avoid since these instances are not what is referenced and used in the end, they simply become garbage.