Constraint Validation Example

How to read this repository

The commits are structured to form a sequential narrative, iteratively and incrementally building toward integrated client- and server-side validation message rendering.

The commits earlier in the sequence use workable and somewhat naive implementations to achieve the desired behavior, and are all covered by tests.

The later commits refine the implementation to a point where some valuable abstractions emerge.

While reading the commits, feel free to skip over commits prefaced by [GENERATED] or [SKIP].

Goals

While most of this code strives to be exemplary user-land integrations with some of these new concepts, it’s a best-effort attempt. The authentication code might not be production-grade security, but it serves its purpose here.

Any concepts that are intended to be extracted to their corresponding frameworks are declared in directories separate from the application code. For example, when possible, Rails extensions are declared within the lib/rails_ext directory, and the app/javascript/initializers/ directory on the JavaScript-side.

As exceptions to that rule, the app/models/concerns and app/controllers/concerns declare extract-able code.

Turbo

The first commit contains the only truly Turbo-specific work. It addresses the Turbo requirements for form submission redirects through a workaround that combines the FlashHash and ActiveRecord::SessionStore.

The rest of the work is Turbo-adjacent.

ActionView and Accessibility

The current ActionView default configurations for <form> element construction don’t create accessible forms and fields.

Some of this work explores some possible extensions to ActionView that could improve Rails’ baked in accessibility.

ActionView and the Constraint Validations API

In addition to building more accessible forms and fields, the ActionView extensions introduce some new concepts and patterns to improve the developer experience around rendering ActiveModel validations in server-generated HTML.

There are also complementary client-side patterns introduced to integrate with the Browser-provided Constraint Validations API (you know, that thing that every Rails app on the planet opts-out of by declaring [novalidate] attributes).

The inception of the concepts behind the JavaScript changes occurred with RailsUJS-integration in mind, but it seems that Turbo will supplant RailsUJS and make it obsolete and deprecated.

There ended up being zero lines of Turbo-dependent JavaScript code.

Testing it out locally

To test this out on your own, clone the repository and run the bin/setup script, then run the test suite by running bin/rails test:all.