Bootstrap Forms for SilverStripe 6

Makes SilverStripe 6 frontend forms render Bootstrap 5 markup automatically. No per-site template work: install, flush, done. The module ships no CSS or JS; it assumes the site already loads Bootstrap 5.

Requirements

• PHP 8.3+
• silverstripe/framework ^6.0
• silverstripe/admin ^3.0

Installation

Add the package to the project's composer repositories (private package), then:

composer require anytech/bootstrap-forms

Run a flush (/dev/build?flush=1 or ?flush=1) so the template manifest picks up the overrides.

What it does

Two extensions applied via _config/extensions.yml:

• FormFieldExtension on SilverStripe\Forms\FormField: appends Bootstrap classes to the rendered element through the updateAttributes hook, so holder wrapper classes stay untouched.
• FormExtension on SilverStripe\Forms\Form: exposes $MessageAlertClass to templates, mapping form message types to alert-danger, alert-success, alert-info, alert-warning.

Template overrides in templates/SilverStripe/Forms/ replace the framework defaults (module templates outrank silverstripe/framework in the $default theme set; site themes still outrank this module):

Template	Change
Includes/Form.ss	Form message as .alert with role="alert", actions in .btn-toolbar.gap-2
FormField_holder.ss	.mb-3 wrapper, .form-label, .invalid-feedback, .form-text
CheckboxField_holder.ss	.form-check wrapper with .form-check-label
CheckboxField_holder_small.ss	.form-check variant for field groups
OptionsetField.ss / CheckboxSetField.ss	li.form-check with .form-check-input / .form-check-label
OptionsetField_holder.ss / CheckboxSetField_holder.ss	fieldset wrapper with the group title as legend.col-form-label.pt-0, plus feedback/description blocks

Field class mapping:

Field	Class
Text-like fields, textarea, file, date/time	form-control
DropdownField, GroupedDropdownField, ListboxField	form-select
CheckboxField	form-check-input
OptionsetField, CheckboxSetField (the ul)	list-unstyled
FormAction	btn plus default variant
Any field with a validation message	is-invalid

Skipped entirely: HiddenField, dataless fields (literal, header, label), GridField, TreeDropdownField, SearchableDropdownField, SearchableMultiDropdownField, and everything rendered inside the CMS (guarded by a LeftAndMain controller check; the cms-forms admin theme also outranks these templates in the admin).

Configuration

Default button variant is btn-primary. Change it per site:

Anytech\BootstrapForms\FormFieldExtension:
  button_variant: btn-outline-secondary

Per-action variants win over the default: any action that already carries a btn-* class (via addExtraClass) keeps it and the default variant is not added.

Overriding

A site theme template at themes/<theme>/templates/SilverStripe/Forms/... overrides this module as usual.