Use a custom form builder; introduce primer_form_for

[camertron]

In attempting to upgrade to PVC v0.0.86 in dotcom, @jonrohan and I ran into a few issues. Version 0.0.86 includes all the re-homed PRF code, which is the main source of friction.

Previously, PRF handled running Primer::Classify.call on system arguments in the Input class, which converts system arugments like ml: 3 into their corresponding CSS class counterparts. This approach works for all inputs except submit buttons, since submit buttons use Primer::ButtonComponent under the hood. The form SubmtButton is an Input, so classification happens at the Input level and then again when all the system arguments are eventually passed to Primer::ButtonComponent. In the development and test environments, classify will raise if it determines you included ml-3 in the list of classes instead of passing it as ml: 3 in the system arguments. This led to errors appearing in dotcom test output since the first classify run done in Input had already converted system arguments to class names before passing them to Primer::ButtonComponent.

I experimented a bit with a flag in the SubmitButton input that disabled classification for the system arguments attached to <input> elements, but realized the forms code runs the same classification process on system arguments attached to labels, etc. The flag seemed like an incomplete solution and a hacky one at that.

Instead I decided to introduce a custom form builder that classifies system arguments right before passing them to rails to generate the <input> elements. I also introduced a helper method, primer_form_with, that mimics rails' form_with helper but automatically uses the custom builder. This is something I've wanted to do for a long time. It also lets us set skip_default_ids automatically, which is important for a11y reasons.

[changeset-bot]

🦋 Changeset detected

Latest commit: ac3a5b9

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@primer/view-components	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR