Morph stimulus reflex element AKA "single element page morph"

[julianrubisch]

Feature

Description

This PR allows to morph over the StimulusReflex::Element that initiated the reflex, like so:

morph element, render(MyComponent.new(...))

This is especially handy when

1. replacing a single partial or ViewComponent, without having to look up the ID
2. when calling this.stimulate with a dedicated element as a target

Why should this be added

Often, when performing a selector morph, one is altering the state of a single piece of the UI and patching it. This PR allows to do so without explicitly stating a selector or AR model/relation,

❗ Attention

depends on stimulusreflex/cable_ready#135

Checklist

• My code follows the style guidelines of this project
• Checks (StandardRB & Prettier-Standard) are passing
• This is not a documentation update

Please note that the best way to suggest changes or updates to the documentation is to join Discord and leave a note in the #docs channel. Any documentation updates posted as PRs cannot be accepted at this time. ❤️

[julianrubisch]

Failing tests are also because of the dependency on cableready/master

[leastbad]

LGTM with a suggestion to memoize update.selector if reasonable.

I did my best to trace the logic of your refactoring; it looks good but to offer you advice I frequently don't take myself: it's easier to click Approve if you keep refactoring and feature implementation in separate PRs. 😉

[julianrubisch]

Re splitting: yes, but at the cost at producing merge conflicts 😜

[julianrubisch]

All done!

[leastbad]

LGTM!