Binder.removeBinding issue

[nbabb]

In Vaadin flow 1.0.5, I have several fields bound to a Binder instance. When I remove a binding (where there are still other bound properties) it is calling unbind. It seems like it should only call unbind when the count of bound properties is zero? Here is the code.

public void removeBinding(String propertyName) {
    Objects.requireNonNull(propertyName, "Property name may not be null");
    Optional.ofNullable(boundProperties.get(propertyName))
            .ifPresent(Binding::unbind);
}

I end up receiving errors after I remove the binding

java.lang.NullPointerException: This Binding is no longer attached to a Binder
at java.base/java.util.Objects.requireNonNull(Objects.java:246) ~[na:na]
at com.vaadin.flow.data.binder.Binder$BindingImpl.validate(Binder.java:1027) ~[flow-data-1.0.5.jar:na]

from my other bound fields that are still using the binding.

Perhaps I'm misunderstanding how this should work?

[rsk-munendra]

I am also getting similar issue when using removeBinding(field).
Seems like when bindings are removed, still the validators for the fields are no dereferenced from the binder.

[lulnope]

The issue is located in Binder class in its protected void removeBindingInternal(Binding<T, ?> binding) method. Currently it looks as follows:

protected void removeBindingInternal(Binding<BEAN, ?> binding) {
        if (bindings.remove(binding)) {
            boundProperties.entrySet()
                    .removeIf(entry -> entry.getValue().equals(binding));
        }
    }

it's missing:
changedBindings.remove(binding)
which should resolve this error:
java.lang.NullPointerException: This Binding is no longer attached to a Binder
Currently a dirty workaround might look like this:

public class WorkaroundBinder<T> extends Binder<T> {

	public WorkaroundBinder() {
		super();
	}

	public WorkaroundBinder(Class<T> beanType, boolean scanNestedDefinitions) {
		super(beanType, scanNestedDefinitions);
	}

	public WorkaroundBinder(Class<T> beanType) {
		super(beanType);
	}

	public WorkaroundBinder(PropertySet<T> propertySet) {
		super(propertySet);
	}
	
	@Override
	protected void removeBindingInternal(Binding<T, ?> binding) {		
		super.removeBindingInternal(binding);
		try {
// if binder does not validate changedBindings is not cleared (possibly a mistake in doWriteIfValid method) as such
// a reference to binding might be left hanging in that set.
// This hack removes hanging reference from changedBindings .
			Field field = Binder.class.getDeclaredField("changedBindings");
			field.setAccessible(true);
			Set<Binding<T, ?>> changedBindings = (Set<Binding<T, ?>>) field.get(this);
			changedBindings.remove(binding);
		} catch (IllegalArgumentException | IllegalAccessException | NoSuchFieldException | SecurityException e) {
			e.printStackTrace();
		}
	}
	
}

[KatriHaapalinna]

Hi, this is the repository for Vaadin Framework (i.e. versions 7 and 8). You seem to be using the newer version, Vaadin Flow, which is located in a different repository.
Please create the issue to the GH repository of Vaadin Flow here: https://github.com/vaadin/flow/issues

[kpy3no]

instead of using remove binding i create only one binding for a field and judging by current state in runtime choose what i'm going to validate