Alert pane: Allows providing contextual feedback messages for typical user actions

[MarcSkovMadsen]

One of the things i use a lot and see other users using in their analytics app are Bootstrap inspired Alerts.

So I would like to contribute one.

The contributed code is ready for review by @philippjfr .

I've chosen

• To implement one Alert with an alert_type parameter instead of a collection of PrimaryAlert, ..InfoAlert, ..., DarkAlert to keep the api in line with Button.
• To add an alert.css file instead of styling inline. That will enable easier custom styling.
• Not to implement a custom Bokeh model supporting the alert_type. Let me know if that is needed.
• To include it in pn.pane instead of pn.widget or pn.components.bootstrap. Those would be alternatives.
• To make the 'stretch_width` by default. I believe this is normal behaviour.
• To not implement the alert-link css class. Instead any <a> link tag will just be styled.
• To not implement the alert-dismissible js functionality. Would be nice to have though.

Alert notebook reference example

Server test example

python -m panel serve 'panel\tests\pane\test_alert.py' --dev --show

Additional Context

This is an example of where the css_classes parameter does not work that well in Panel @philippjfr . In order to get the proper styling you need to define .bk.alert-primary instead of .alert-primary to get specific enough. That means you can't copy-paste/ or include one of the many existing style sheets out there. This is friction. :-)

[philippjfr]

I've heard some hopeful things about eventually being able to remove the css prefixing but I doubt that'll happen in the near future.

[philippjfr]

Thanks for the contribution though, very sensible addition.

[MarcSkovMadsen]

A small step for man :-)

[philippjfr]

Apart from my minor two comments this is mergeable. Could you maybe also generate a thumbnail for the gallery and upload it here? That way I can add it to the CDN and it'll find it during the next doc build.

[MarcSkovMadsen]

One question @philippjfr is whether the type and colors of button and Alert should somehow be aligned?

And maybe even aligned with the Card I'm contributing. Maybe the card should have a card_type and associated header colors?

[philippjfr]

One question @philippjfr is whether the type and colors of button and Alert should somehow be aligned?

Might be nice, maybe we should have a saturated=True/False option to toggle between the pastel and fully saturated colors?

[MarcSkovMadsen]

One question @philippjfr is whether the type and colors of button and Alert should somehow be aligned?

Might be nice, maybe we should have a saturated=True/False option to toggle between the pastel and fully saturated colors?

...hmmmm.... I'm not an expert on colors. Try to stay out of it but always gets to spend a lot of time on it. Any experts around?

[philippjfr]

Merging for now, can add the saturated colors later.