Add link_button_to helper

This provides an easier migration path for links that look like buttons
than using `Pajamas::ButtonComponent` itself. This is because the method
signature is much more similar to `link_to` than
`Pajamas::ButtonComponent`.

It's also slightly less verbose, which seems reasonable for such
a common use case.

app/helpers/application_helper.rb

@@ -464,6 +464,73 @@ def gitlab_ui_form_with(**args, &block)
     form_with(**args.merge({ builder: ::Gitlab::FormBuilders::GitlabUiFormBuilder }), &block)
   end
 
+  # Creates a link that looks like a button.
+  #
+  # It renders a Pajamas::ButtonComponent.
+  #
+  # It has the same API as `link_to`, but with some additional options
+  # specific to button rendering.
+  #
+  # Examples:
+  #   # Default button
+  #   link_button_to _('Foo'), some_path
+  #
+  #   # Default button using a block
+  #   link_button_to some_path do
+  #     _('Foo')
+  #   end
+  #
+  #   # Confirm variant
+  #   link_button_to _('Foo'), some_path, variant: :confirm
+  #
+  #   # With icon
+  #   link_button_to _('Foo'), some_path, icon: 'pencil'
+  #
+  #   # Icon-only
+  #   # NOTE: The content must be `nil` in order to correctly render. Use aria-label
+  #   # to ensure the link is accessible.
+  #   link_button_to nil, some_path, icon: 'pencil', 'aria-label': _('Foo')
+  #
+  #   # Small button
+  #   link_button_to _('Foo'), some_path, size: :small
+  #
+  #   # Secondary category danger button
+  #   link_button_to _('Foo'), some_path, variant: :danger, category: :secondary
+  #
+  # For accessibility, ensure that icon-only links have aria-label set.
+  def link_button_to(name = nil, options = nil, html_options = nil, &block)
+    if block
+      html_options = options
+      options = name
+      name = block
+    end
+
+    html_options ||= {}
+
+    # Ignore args that don't make sense for links, like disabled, loading, etc.
+    options_for_button = %i[
+      category
+      variant
+      size
+      block
+      selected
+      icon
+      target
+      method
+    ]
+
+    args = html_options.slice(*options_for_button)
+    html_options = html_options.except(*options_for_button)
+
+    if block
+      render Pajamas::ButtonComponent.new(href: options, **args, button_options: html_options), &block
+    else
+      render Pajamas::ButtonComponent.new(href: options, **args, button_options: html_options) do
+        name
+      end
+    end
+  end
+
   private
 
   def browser_id

spec/helpers/application_helper_spec.rb

@@ -619,6 +619,125 @@ def stub_controller_method(method_name, value)
     end
   end
 
+  describe '#link_button_to', feature_category: :design_system do
+    let(:content) { 'Button content' }
+    let(:options) { '#' }
+    let(:html_options) { {} }
+
+    RSpec.shared_examples 'basic behavior' do
+      it 'renders a basic link button' do
+        expect(subject.name).to eq('a')
+        expect(subject.classes).to include(*%w[gl-button btn btn-md btn-default])
+        expect(subject.attr('href')).to eq(options)
+        expect(subject.content.strip).to eq(content)
+      end
+
+      describe 'variant option' do
+        let(:html_options) { { variant: :danger } }
+
+        it 'renders the variant class' do
+          expect(subject.classes).to include('btn-danger')
+        end
+      end
+
+      describe 'category option' do
+        let(:html_options) { { category: :tertiary } }
+
+        it 'renders the category class' do
+          expect(subject.classes).to include('btn-default-tertiary')
+        end
+      end
+
+      describe 'size option' do
+        let(:html_options) { { size: :small } }
+
+        it 'renders the small class' do
+          expect(subject.classes).to include('btn-sm')
+        end
+      end
+
+      describe 'block option' do
+        let(:html_options) { { block: true } }
+
+        it 'renders the block class' do
+          expect(subject.classes).to include('btn-block')
+        end
+      end
+
+      describe 'selected option' do
+        let(:html_options) { { selected: true } }
+
+        it 'renders the selected class' do
+          expect(subject.classes).to include('selected')
+        end
+      end
+
+      describe 'target option' do
+        let(:html_options) { { target: '_blank' } }
+
+        it 'renders the target attribute' do
+          expect(subject.attr('target')).to eq('_blank')
+        end
+      end
+
+      describe 'method option' do
+        let(:html_options) { { method: :post } }
+
+        it 'renders the data-method attribute' do
+          expect(subject.attr('data-method')).to eq('post')
+        end
+      end
+
+      describe 'icon option' do
+        let(:html_options) { { icon: 'remove' } }
+
+        it 'renders the icon' do
+          icon = subject.at_css('svg.gl-icon')
+          expect(icon.attr('data-testid')).to eq('remove-icon')
+        end
+      end
+
+      describe 'icon only' do
+        let(:content) { nil }
+        let(:html_options) { { icon: 'remove' } }
+
+        it 'renders the icon-only class' do
+          expect(subject.classes).to include('btn-icon')
+        end
+      end
+
+      describe 'arbitrary html options' do
+        let(:content) { nil }
+        let(:html_options) { { data: { foo: true }, aria: { labelledby: 'foo' } } }
+
+        it 'renders the attributes' do
+          expect(subject.attr('data-foo')).to eq('true')
+          expect(subject.attr('aria-labelledby')).to eq('foo')
+        end
+      end
+    end
+
+    describe 'without block' do
+      subject do
+        tag = helper.link_button_to content, options, **html_options
+        Nokogiri::HTML.fragment(tag).first_element_child
+      end
+
+      include_examples 'basic behavior'
+    end
+
+    describe 'with block' do
+      subject do
+        tag = helper.link_button_to options, **html_options do
+          content
+        end
+        Nokogiri::HTML.fragment(tag).first_element_child
+      end
+
+      include_examples 'basic behavior'
+    end
+  end
+
   describe '#page_class' do
     subject(:page_class) do
       helper.page_class.flatten