Implement field_id in terms of the FormBuilder's namespace: option

[seanpdoyle]

When constructing the field's [id] attribute, the current
FormBuilder#field_id implementation (introduced in 59ca21c) ignores the
namespace: option.

This commit incorporates any namespace by prepending it to the
@object_name.

[jonathanhefner]

Seems like it would be good to include this. 👍

[seanpdoyle]

@jonathanhefner I've since discovered that during the Tags::Base class call to add_default_name_and_id relies on a private tag_id:

rails/actionview/lib/action_view/helpers/tags/base.rb

Lines 95 to 105 in 3fcadfb

	def add_default_name_and_id(options)
	index = name_and_id_index(options)
	options["name"] = options.fetch("name") { tag_name(options["multiple"], index) }
	if generate_ids?
	options["id"] = options.fetch("id") { tag_id(index) }
	if namespace = options.delete("namespace")
	options["id"] = options["id"] ? "#{namespace}_#{options['id']}" : namespace
	end
	end
	end

That tag_id method invokes @template_object.field_id instead of delegating to the form instance:

rails/actionview/lib/action_view/helpers/tags/base.rb

Lines 119 to 121 in 3fcadfb

	def tag_id(index = nil)
	@template_object.field_id(@object_name, @method_name, index: index)
	end

This means that after these changes, user-land calls to form.field_id will incorporate any namespace: option passed in. However, since the internals skip the FormBuilder instance and call field_id on the @template_object directly, any FormBuilder options are inaccessible at that point, so the built-in [id] generation code will not be affected by these changes.

[jonathanhefner]

This means that after these changes, user-land calls to form.field_id will incorporate any namespace: option passed in. However, since the internals skip the FormBuilder instance and call field_id on the @template_object directly, any FormBuilder options are inaccessible at that point, so the built-in [id] generation code will not be affected by these changes.

I'm not as familiar with those internals, but it sounds like you are saying this change should be pushed down into @template.field_id, and add_default_name_and_id + tag_id should be modified to thread options["namespace"] to it. Is that accurate?

[seanpdoyle]

@jonathanhefner maybe! I'll push on that a bit.

[seanpdoyle]

@rafaelfranca since field_id was introduced as part of 7.0.0, would this be a good change to consider for the next release candidate?