Add generic component block

app/models/landing_page/block/component.rb

@@ -0,0 +1,45 @@
+module LandingPage::Block
+  class Component < Base
+    ALLOWED_COMPONENTS = %w[
+      action_link
+      attachment
+      back_link
+      big_number
+      button
+      cards
+      chat_entry
+      contents_list
+      copy_to_clipboard
+      details
+      document_list
+      glance_metric
+      govspeak
+      heading
+      image_card
+      inset_text
+      inverse_header
+      lead_paragraph
+      list
+      notice
+      organisation_logo
+      page_title
+      previous_and_next_navigation
+      print_link
+      share_links
+      warning_text
+    ].freeze
+
+    attr_reader :component_name
+
+    def initialize(block_hash, landing_page)
+      super
+
+      @component_name = data["component_name"]
+      raise "Component #{component_name} is not in the allowed list of components for this block" unless ALLOWED_COMPONENTS.include?(component_name)
+    end
+
+    def component_attributes
+      data.except("type", "component_name").symbolize_keys
+    end
+  end
+end

app/views/landing_page/blocks/_component.html.erb

@@ -0,0 +1 @@
+<%= render "govuk_publishing_components/components/#{block.component_name}", block.component_attributes %>

docs/building_blocks_for_flexible_content.md

@@ -31,6 +31,7 @@ Simple blocks generally render one component or "thing". They can either be rend
 
 - [Action Link](#action-link)
 - [Big Number](#big-number)
+- [Component](#component)
 - [Document List](#document-list)
 - [Govspeak](#govspeak)
 - [Heading](#heading)
@@ -61,6 +62,17 @@ A wrapper around the [Big number component](https://components.publishing.servic
   label: amount of money that looks big
 ```
 
+#### Component
+
+Renders whatever component from the publishing components gem is specified with the `component_name` value. All attributes _except_ `component_name` and `type` are passed directly to the component. Note that `component_name` should be the component in snake case (ie as it appears at the end of the url in the component guide). The example here will render identically to the Big Number example directly above, for instance.
+
+```yaml
+- type: component
+  component_name: big_number
+  number: £75m
+  label: amount of money that looks big
+```
+
 #### Document List
 
 A wrapper around the [Document list component](https://components.publishing.service.gov.uk/component-guide/document_list) with a title that will only appear if there are any items in the list (if the list is entirely empty the heading will not appear either)

spec/fixtures/landing_page.yaml

@@ -73,6 +73,9 @@ blocks:
     <a href="/landing-page/sub-page-1">Visit sub-page 1</a>
 - type: govspeak
   content: <p>Here's some more content!</p>
+- type: component
+  component_name: big_number
+  number: 555
 - type: quote
   text: "Here's a quote!"
   cite: "I said this"

spec/models/landing_page/block/component_spec.rb

@@ -0,0 +1,36 @@
+RSpec.describe LandingPage::Block::Component do
+  it_behaves_like "it is a landing-page block"
+
+  let(:blocks_hash) do
+    { "type" => "component",
+      "component_name" => "big_number",
+      "number" => 123,
+      "label" => "Number of things" }
+  end
+  let(:subject) { described_class.new(blocks_hash, build(:landing_page)) }
+
+  describe "allowed list of components" do
+    it "allows components on the list" do
+      expect { subject }.not_to raise_error
+    end
+
+    context "when the component_name is not in the allowed list" do
+      let(:blocks_hash) do
+        { "type" => "component",
+          "component_name" => "layout_for_public",
+          "number" => 123,
+          "label" => "Number of things" }
+      end
+
+      it "raises an error" do
+        expect { subject }.to raise_error("Component layout_for_public is not in the allowed list of components for this block")
+      end
+    end
+  end
+
+  describe "#component_attributes" do
+    it "returns all attributes except the type and component_name" do
+      expect(subject.component_attributes).to eq(number: 123, label: "Number of things")
+    end
+  end
+end