BC break introduced in 2.8.4

[davidwindell]

Tests to demonstrate the breaking change in behaviour introduced by 2.8.4 (this test will pass in 2.8.3)

Discussion in #102

[weierophinney]

I've looked into this, and it's pretty much as simple as changing this block within bindValues():

if (!array_key_exists($name, $values)) {
    if (!($element instanceof Collection)) {
        continue;
    }

    $values[$name] = [];
}

to:

if (!array_key_exists($name, $values)) {
    continue;
}

However, that makes the test introduced in #19 fail (FormTest::testShouldHydrateEmptyCollection()).

The question is: which is the correct behavior?

The argument @davidwindell makes is that the change from #19 introduces a BC break at this point. What was argued on #19 was that the previous behavior was incorrect. As I noted when analyzing an iteration of that pull request:

Essentially, this patch has exposed a subtle bug that was masquerading as a feature. The test was checking to ensure that a value in a nested fieldset, when resubmitted, would not change. What's interesting is that, in stepping through the code, it appears that the reason it worked previously was because the nested fieldset was being silently ignored during binding. The test was passing, but because the scenario it described just happened to also be the result of an issue.

I'm really unsure how to proceed here. I'm dismayed that there is a change in behavior that is affecting users, but, on the other hand, reverting the patch also results in behavior that affects users. About the only thing I can think of at this point to accomplish both goals is to add a flag to allow opting into one or the other behaviors, and, frankly, flags are a maintenance nightmare.

Thoughts?

[weierophinney]

Okay, looks like 106 solves it... via a "flag" passed to the collection and/or form when calling bindValues().. Will close this when I merge that.

[davidwindell]

Thank you very much for taking the time to look into this @weierophinney and @svycka for your patch.

Zf3 here we come!