add support for onClick link override and fix Bulma sample

[slightfoot]

Description

I noticed the Bulma CSS example tabs no longer saved their state. This got me looking and a classic issue was found. There was a link tag used within the li which contains the onClick handler.

jaspr/apps/jaspr_pad/samples/bulma/tabs.dart

Line 53 in 52533b9

yield li(

This means the link will always reload the page and not let the outer onClick handler take place. It is still correct however to put a link inside the li tag as anchors will still action even if javascript is disabled, they also are followed by bots and screen-readers for the visually impared. So moving the onClick handler from the li to the a tag would be the correct fix.

This leads to the issue resolved here. The default events() function does not allow for preventing the default handler to execute. Which is correct behaviour as their is very little now apart from a tags that have the default event behaviour.

This can be resolved a few ways:

1. onClick handler can return false (classic html 4)
2. onClick can call preventDefault on the event given to the callback (html 5)

So this PR adds a onClick parameter to the a tag function builder that injects the event preventDefault action so the link does not action and cause a browser navigation event. If a Jaspr user does not want this behaviour that can still override the events parameter and use the events() generator.

https://github.com/slightfoot/jaspr/blob/9871addf7bfcc03eadf948d37ce3a05f4b61409f/packages/jaspr/lib/src/components/html/text.dart#L56

https://github.com/slightfoot/jaspr/blob/9871addf7bfcc03eadf948d37ce3a05f4b61409f/apps/jaspr_pad/samples/bulma/tabs.dart#L56

Warning

This is untested.

Type of Change

Ready Checklist

• I've read the Contribution Guide.
• In case this PR changes one of the core packages, I've modified the respective CHANGELOG.md file using
  the semantic_changelog format.
• I updated/added relevant documentation (doc comments with ///).
• I added myself to the AUTHORS file (optional, if you want to).

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docs.page/schultek/jaspr~393

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[github-actions]

Package Version Report

The following packages have been updated:
jaspr : 0.18.0 -> 0.18.1
jaspr_builder : 0.18.0 -> 0.18.1
jaspr_cli : 0.18.0 -> 0.18.1
jaspr_test : 0.18.0 -> 0.18.1

[schultek]

Generally I like this very much, I had this same problem many times but never thought of just defaulting to doing preventDefault in a custom handler.

Though as you see in my comment below the solution cannot directly modify the text.dart file as it is generated.

[slightfoot]

@schultek patches made, should be good now

[schultek]

LGTM