[Idea] Bi-directional property accessor

[EotT123]

It would be useful to allow method references to properties to be interpreted as both getters and setters. This would enable a single reference to a property to serve as a bi-directional accessor, which could simplify and unify design around property manipulation.

Example:

// Example class with a property
public class Foo{
    @var String bar;
}

// Method accepting a property accessor
public void doSomething(Foo foo, PropertyAccessor<Foo, String> propertyAccessor){
   String bar = propertyAccessor.get(foo);
   ...
   propertyAccessor.set(foo, bar);
}

// Calling the method
doSomthing(new Foo(), Foo::bar);

Do support this behaviour, Manifold would have to replace the method reference for the property with a new PropertyAccessor object, which encapsulates both getter and setter logic for the property.

Here’s a real example from SubTools, where valueGetter and valueSetter are specified separately:

OPTIONS_LANGUAGE(createSettingEnum(Language.class)
	.rootElementFunction(SettingsControl::getSettings)
	.valueGetter(Settings::getLanguage)
	.valueSetter(Settings::setLanguage)
	.defaultValue(Language.ENGLISH)),
OPTIONS_ALWAYS_CONFIRM(createSettingBoolean()
	.rootElementFunction(SettingsControl::getSettings)
	.valueGetter(Settings::isOptionsAlwaysConfirm)
	.valueSetter(Settings::setOptionsAlwaysConfirm)
	.defaultValue(false)),
OPTIONS_CONFIRM_MAPPING(createSettingBoolean()
	.rootElementFunction(SettingsControl::getSettings)
	.valueGetter(Settings::isOptionsConfirmProviderMapping)
	.valueSetter(Settings::setOptionsConfirmProviderMapping)
	.defaultValue(true)),
...

With support for PropertyAccessor, this could be simplified to:

OPTIONS_LANGUAGE(createSettingEnum(Language.class)
	.rootElementFunction(SettingsControl::getSettings)
	.valueAccessor(Settings::language)
	.defaultValue(Language.ENGLISH)),
OPTIONS_ALWAYS_CONFIRM(createSettingBoolean()
	.rootElementFunction(SettingsControl::getSettings)
	.valueAccessor(Settings::optionsAlwaysConfirm)
	.defaultValue(false)),
OPTIONS_CONFIRM_MAPPING(createSettingBoolean()
	.rootElementFunction(SettingsControl::getSettings)
	.valueAccessor(Settings::optionsConfirmProviderMapping)
	.defaultValue(true)),

Support for PropertyAccessor should be limited to fields annotated with @var (excluding those with private @get or @set), or cases where both a public getter and setter method are defined (or a combination).