Multiple effect invocations if reading the same signal multiple times

[Legioth]

Description of the bug

A component effect that reads the same signal multiple times is invoked multiple times when that signal is changed.

Expected behavior

The effect should be run only once for a single signal value change.

Minimal reproducible example

ValueSignal<String> signal = new ValueSignal<>("Initial");

Signal.effect(this, () -> {
    Notification.show(signal.get());
    signal.get();
    signal.get();
});

add(new Button("Update", click -> {
    signal.update(value -> value + " update ");
}));

Every time the button is clicked, three notifications are shown whereas only one notification is expected.

Versions

• Vaadin / Flow version: 25.1.0-rc2

[mshabarov]

Fun fact that some test is actually checking that two invocations for two reads are expected 🙈

        binder.forField(firstNameField).withValidator((String value) -> {
            validatorCalls.incrementAndGet();
            return !value.isEmpty()
                    // multiple calls to same valueSignal()
                    && !lastNameBinding.valueSignal().get().isEmpty()
                    && !lastNameBinding.valueSignal().get().isEmpty();
        }, "First and last name are required").bind("firstName");

        // value change runs revalidation for both Signal.get() calls in the
        // validator
        assertEquals(5, validatorCalls.get());