Another unexpected break in behavior for wp_new_user_notification()

[danielbachhuber]

wp_new_user_notification() originally sent two emails if $password was provided: one to the admin, and another to the created user.

r33620 "restored" this behavior, but then r34116 disabled this behavior because the deprecated $password argument isn't checked in this conditional:

 if ( 'admin' === $notify || empty( $notify ) ) {
    return;
}

If $password is provided, I'd expect the conditional to fail.

I think that $notify could default to 'both', in which case empty( $notify ) could just be removed.

Discovered in ​https://github.com/wp-cli/wp-cli/pull/2163

[ocean90]

In 35735:

Passwords: Support the pre-4.3 behavior of wp_new_user_notification().

Hello, it's me again. A pluggable function named wp_new_user_notification(). A few months ago, after [33023], I have lost my second parameter $plaintext_pass. But thanks to [33620] I got a new one.
Bad idea - It hasn't had the same behavior as my previous parameter.
To solve that the second parameter got deprecated and reintroduced as the third parameter in [34116]. I was happy again, for a short time.
You remember my lost friend $plaintext_pass? No? Well, if its value was empty no notification was sent to the user. This behavior was still lost. And that's what this change is about: Don't notify a user if a plugin uses wp_new_user_notification( $user_id ).

You're asking if I'm happy now? Dunno, but maybe you have learned something about pluggable functions, have you?

Props danielbachhuber.
Fixes #34377.

[helen]

This close to 4.4, no hint of 4.3.2 in sight.