Support Rails 5.1+ `form_with` style (`form_for` will eventually go away in Rails 6.x)

[krtschmr]

rails/rails#25197

[mattbrictson]

Thanks for logging this issue! It sounds like this is an important change.

As for the impact to this project: Do you expect it is just a matter of adding bootstrap_form_with that follows the form_with semantics, or is there more to it than that?

[krtschmr]

it is a long road for rails.
starting 5.1 we will have 3 methods form_with, form_for, form_tag. _for and _tag are soft-deprecated and propably with 6.0 or 6.1 rails will issue a deprecation-warning and then remove the methods maybe with 6.2 or later.

actually we should implement the complete form_with as a bootstrap_form_with. i checked the form-builder and if i understand it correctly, we can easy re-use all the component-builders but i'm unsure how to implement.

https://github.com/rails/rails/blob/612572746c311b69d617a7f0d6eb6bdbad82780c/actionview/lib/action_view/helpers/form_helper.rb#L715

https://github.com/rails/rails/blob/612572746c311b69d617a7f0d6eb6bdbad82780c/actionview/lib/action_view/helpers/form_tag_helper.rb#L67

[mattbrictson]

@krtschmr do you have a Rails 5.1 project that you are actively developing? And further would you use bootstrap_form_with on that project if it was available to you?

The reason I ask is that I have no plans in the short term to use form_with in my Rails projects, so I don't feel comfortable building this feature by myself. It doesn't make sense to add a feature if we have no idea whether it works in the real world.

If you have a good use case for it and would be willing to test it for me, then perhaps I will give it a shot.

[lcreid]

I have a Rails 5.1 project and I'd like to use bootstrap_form_with in it. The trick is, I also need to use Bootstrap 4. I notice that the bootstrap-4 branch isn't up-to-date with some changes for Rails 5.1. Should I merge or rebase the bootstrap-4 branch from master, and then add bootstrap_form_with? If so, which (merge or rebase)?

[lcreid]

I'm close to having a PR ready for this. form_with doesn't generate ids and classes for form elements the way the form_for and form_tag helpers did. I created a bunch of tests for form_with, basically testing what the existing tests for form_for and form_tag do, and they're all green, but I need to dig deeper on a couple of the cases before I feel comfortable that what I did is in fact correct. I just wanted to go on the record that I'm working on this issue, and I'm making some progress.

[lcreid]

In DHH's original Rails issue that proposed form_with, rails/rails#25197, his first goal was to get rid of the default generation of DOM id and classes from the form helpers. Once form_with was released, some people raised an issue with the lack of default DOM ids and classes (e.g. rails/rails#29014). However, it looks like the default behaviour of form_with is going to remain "no default DOM ids or classes."

The lack of default DOM id means that the way the bootstrap_form helpers generate labels for fields doesn't give the best user experience, since the labels are no longer clickable. I tried a few implementations to deal with it. None of them were particularly difficult. However, I think from the documentation and learning point of view, it would be better for bootstrap_form_with to behave like form_with. In this case, that means helpers under bootstrap_form_with should not generate any DOM ids or classes that the underlying Rails helpers wouldn't generate.

The upshot is that users of bootstrap_form_with will have to specify an id for form elements for which they want the label to be clickable. This is the same change in behaviour that all Rails programmers will have to learn when switching from form_for to form_with.

There is an open PR on Rails (rails/rails#29439) to add a skip_default_ids = false option to form_with. It would cause helpers used with form_with to generate default DOM ids and classes, the way they do for form_for. If Rails PR 29439 is merged into Rails, I believe it would work with bootstrap_form_with, meaning that the Rails helpers would generate default DOM ids and classes, and bootstrap_form_with helpers would generate labels with the expected for attribute. Of course, we'll have to test it if/when the PR is merged into Rails.

I hope I'll be able to submit a PR today for this issue, based on the approach I mentioned above. If anyone has any comments before I submit the PR, I'd love to hear them.

[lcreid]

I wanted to beef up my testing before submitting the PR. Good thing I did, as it has exposed some interesting challenges. I'm having to dig into this code more than I had expected. I'll try to get a PR together as soon as I can.