Show only alerts with supported types

[rsamoilov]

Flash messages are not something, that should always be displayed as an alert.

Flash can be used to store some service values or states and it's not expected behavior to show that values as alerts.
For example, if I want to render some form with default values from another action, I could use flash to store that values.

[toadkicker]

I don't want to lock people into four types of statuses.

[toadkicker]

I don't like this commit because flash shouldn't be used for storing service values or states. Just because Twitter Bootstrap uses the standard logging level names to style the alert box doesn't mean we only check for those four statuses. It makes the gem less flexible and doesn't allow developers to use custom alert levels.

[rsamoilov]

Why not? It's a common case to use flash for states.
I didn't dig a lot into sources, but it looks like devise uses flash in such way too - https://github.com/plataformatec/devise/blob/master/lib/devise/failure_app.rb#L80

If user needs a couple of warnings on page, with your implementation he could do it with something
like this: flash[:warning] = ['warning 1', 'warning 2']

[toadkicker]

If I want flash[:whatever] to be styled like an error alert, this commit forces me to use flash[:error] to get it to display. The flash method accepts any symbol, and a library shouldn't stop a developer from doing that while still getting the UI to do what it wants. It's not about multiple messages, its about allowing the flash method to work as expected.

[rsamoilov]

The flash method accepts any symbol, and a library shouldn't stop a developer from doing that

Exactly. And with previous implementation library stopped developer from using flash to store some service values, which are not desirable to be displayed.

This commit could be inverted - display all messages from flash except messages under some key, :service_values for example. But I personally don't see reason, which could force me to store error message in flash[:hello] or flash[:whatever]

This could be meaningful for displaying a couple of errors. So, I could write flash[:first_error], flash[:second_error] = 'error 1', 'error 2' and these errors would have not been displayed. But with your implementation I would write flash[:error] = ['error 1', 'error 2']. That's what I was talking about.

[nick-desteffen]

http://blog.remarkablelabs.com/2012/12/register-your-own-flash-types-rails-4-countdown-to-2013