ToggleSwitch form (#1715)

Co-authored-by: Cameron Dutro <camertron@gmail.com>

.changeset/lovely-boats-hang.md

@@ -0,0 +1,5 @@
+---
+'@primer/view-components': patch
+---
+
+Add Primer::Forms::ToggleSwitchForm

app/forms/example_toggle_switch_form.rb

@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+# :nodoc:
+class ExampleToggleSwitchForm < Primer::Forms::ToggleSwitchForm
+  def initialize(**system_arguments)
+    super(name: :example_field, label: "Example", **system_arguments)
+  end
+end

app/forms/example_toggle_switch_form/example_field_caption.html.erb

@@ -0,0 +1 @@
+My <em>favorite</em> caption.

lib/primer/forms/dsl/toggle_switch_input.rb

@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+
+module Primer
+  module Forms
+    module Dsl
+      # :nodoc:
+      class ToggleSwitchInput < Input
+        attr_reader :name, :label, :src, :csrf
+
+        def initialize(
+          name:,
+          label:,
+          src:,
+          csrf: nil,
+          **system_arguments
+        )
+          @name = name
+          @label = label
+          @src = src
+          @csrf = csrf
+
+          super(**system_arguments)
+        end
+
+        def to_component
+          ToggleSwitch.new(input: self)
+        end
+
+        def type
+          :toggle_switch
+        end
+      end
+    end
+  end
+end

lib/primer/forms/toggle_switch.html.erb

@@ -0,0 +1,17 @@
+<%= content_tag(:div, **@form_group_arguments) do %>
+  <span style="flex-grow: 1">
+    <%= builder.label(@input.name, **@input.label_arguments) do %>
+      <%= @input.label %>
+    <% end %>
+    <%= render(Caption.new(input: @input)) %>
+  </span>
+  <%
+    csrf = @input.csrf || @view_context.form_authenticity_token(
+      form_options: {
+        method: :post,
+        action: @input.src
+      }
+    )
+  %>
+  <%= render(Primer::Alpha::ToggleSwitch.new(src: @input.src, csrf: csrf)) %>
+<% end %>

lib/primer/forms/toggle_switch.rb

@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+module Primer
+  module Forms
+    # :nodoc:
+    class ToggleSwitch < BaseComponent
+      delegate :builder, :form, to: :@input
+
+      def initialize(input:)
+        @input = input
+        @input.add_label_classes("FormControl-label")
+
+        @form_group_arguments = { class: "d-flex" }
+
+        @form_group_arguments[:hidden] = "hidden" if @input.hidden?
+      end
+    end
+  end
+end

lib/primer/forms/toggle_switch_form.rb

@@ -0,0 +1,74 @@
+# frozen_string_literal: true
+
+module Primer
+  module Forms
+    # Toggle switches are designed to submit an on/off value to the server immediately
+    # upon click. For that reason they are not designed to be used in "regular" forms
+    # that have other fields, etc. Instead they should be used independently via this
+    # class.
+    #
+    # ToggleSwitchForm can be used directly or via inheritance.
+    #
+    # Via inheritance:
+    #
+    # # app/forms/my_toggle_form.rb
+    # class MyToggleForm < Primer::Forms::ToggleSwitchForm
+    #   def initialize(**system_arguments)
+    #     super(name: :foo, label: "Foo", src: "/foo", **system_arguments)
+    #   end
+    # end
+    #
+    # # app/views/some_view.html.erb
+    # <%= render(MyToggleForm.new) %>
+    #
+    # Directly:
+    #
+    # # app/views/some_view.html.erb
+    # <%= render(
+    #   Primer::Forms::ToggleSwitchForm.new(
+    #     name: :foo, label: "Foo", src: "/foo"
+    #   )
+    # ) %>
+    #
+    class ToggleSwitchForm < Primer::Forms::Base
+      # Define the form on subclasses so render(Subclass.new) works as expected.
+      def self.inherited(base)
+        base.form do |toggle_switch_form|
+          input = Dsl::ToggleSwitchInput.new(
+            builder: toggle_switch_form.builder, form: self, **@system_arguments
+          )
+
+          toggle_switch_form.send(:add_input, input)
+        end
+      end
+
+      # Define the form on self so render(ToggleSwitchForm.new) works as expected.
+      inherited(self)
+
+      # Override to avoid accepting a builder argument. We create our own builder
+      # on render. See the implementation of render_in below.
+      def self.new(**options)
+        allocate.tap { |obj| obj.send(:initialize, **options) }
+      end
+
+      def initialize(**system_arguments)
+        @system_arguments = system_arguments
+      end
+
+      # Unlike other instances of Base, ToggleSwitchForm defines its own form and
+      # is not given a Rails form builder on instantiation. We do this mostly for
+      # ergonomic reasons; it's much less verbose than if you were required to
+      # call form_with/form_for, etc. That said, the rest of the forms framework
+      # assumes the presence of a builder so we create our own here. A builder
+      # cannot be constructed without a corresponding view context, which is why
+      # we have to override render_in and can't create it in the initializer.
+      def render_in(view_context, &block)
+        @builder = Primer::Forms::Builder.new(
+          nil, nil, view_context, {}
+        )
+
+        super
+      end
+    end
+  end
+end

previews/primer/forms/forms_preview.rb

@@ -39,6 +39,8 @@ def multi_input_form; end
       def name_with_question_mark_form; end
 
       def immediate_validation_form; end
+
+      def example_toggle_switch_form; end
     end
   end
 end

previews/primer/forms/forms_preview/example_toggle_switch_form.html.erb

@@ -0,0 +1 @@
+<%= render(ExampleToggleSwitchForm.new(csrf: "let_me_in", src: toggle_switch_index_path)) %>

test/lib/primer/forms/toggle_switch_form_test.rb

@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+require "lib/test_helper"
+
+class Primer::Forms::ToggleSwitchFormTest < Minitest::Test
+  include Primer::ComponentTestHelpers
+
+  def test_it_renders_with_a_name
+    bogus_csrf = "let me in"
+    render_inline(ExampleToggleSwitchForm.new(csrf: bogus_csrf, src: "/toggle_switch"))
+
+    assert_selector "toggle-switch[src='/toggle_switch'][csrf='#{bogus_csrf}']"
+  end
+
+  def test_can_render_without_subclass
+    render_inline(
+      Primer::Forms::ToggleSwitchForm.new(
+        name: :example_field,
+        label: "Example",
+        src: "/toggle_switch"
+      )
+    )
+
+    assert_selector "toggle-switch[src='/toggle_switch']"
+  end
+end