Improve how documentation pages are rendered

* Extracts an object to encapsulate rendering a given page (which also
  allows us to explicitly test it),
* Allows us to render pages without the YAML frontmatter, which was
  making a mess of the README and Contributing Guide,

CONTRIBUTING.md

@@ -1,6 +1,4 @@
----
-title: Contributing Guide
----
+# Contributing Guide
 
 ## Code of Conduct
 

README.md

@@ -1,7 +1,4 @@
----
-title: Administrate
-home: true
----
+# Administrate
 
 [![CircleCI](https://img.shields.io/circleci/project/github/thoughtbot/administrate.svg)](https://circleci.com/gh/thoughtbot/administrate/tree/master)
 [![Gem Version](https://badge.fury.io/rb/administrate.svg)](https://badge.fury.io/rb/administrate)

spec/example_app/app/controllers/docs_controller.rb

@@ -1,97 +1,32 @@
 class DocsController < ApplicationController
-  SPECIAL_FILES = [
-    {
-      file: 'CONTRIBUTING',
-      page: 'contributing'
-    }
-  ].freeze
-
-  REDCARPET_CONFIG = {
-    fenced_code_blocks: true,
-    autolink: true,
-  }.freeze
-
   def index
-    render_page "README"
+    render_page("README", "README")
   end
 
   def show
-    render_correct_page
-  end
-
-  private
-
-  def find_special_file
-    SPECIAL_FILES.select { |page| page[:page] == params[:page] }.first
-  end
-
-  def render_correct_page
-    if !find_special_file.nil?
-      render_page(find_special_file[:file])
+    case params[:page]
+    when "contributing"
+      render_page("contributing", "Contributing Guide")
     else
       render_page("docs/#{params[:page]}")
     end
   end
 
-  def render_page(name)
-    path = full_page_path(name)
+  private
+
+  def render_page(name, title = nil)
+    page = DocPage.find(name)
 
-    if File.exist?(path)
-      contents = parse_document(path)
-      @page_title = contents.title
-      @page_title_suffix = contents.title_suffix
+    if page
+      @page_title = title || page.title
+      @page_title_suffix = " - Administrate"
       # rubocop:disable Rails/OutputSafety
-      render layout: "docs", html: contents.body.html_safe
+      render layout: "docs", html: page.body.html_safe
       # rubocop:enable Rails/OutputSafety
     else
-      render file: "#{Rails.root}/public/404.html",
+      render file: Rails.root.join("public/404.html"),
              layout: false,
              status: :not_found
     end
   end
-
-  def full_page_path(page)
-    Rails.root + "../../#{page}.md"
-  end
-
-  def parse_document(path)
-    text = File.read(path)
-    DocumentParser.new(text)
-  end
-
-  class DocumentParser
-    def initialize(source_text)
-      front_matter_parsed = FrontMatterParser::Parser.new(:md).call(source_text)
-      @source_text = front_matter_parsed.content
-      @metadata = front_matter_parsed.front_matter
-    end
-
-    def body
-      @body ||=
-        begin
-          renderer = Redcarpet::Render::HTML
-          markdown = Redcarpet::Markdown.new(renderer, REDCARPET_CONFIG)
-
-          source_text_with_heading = <<~MARKDOWN
-            # #{title}
-
-            #{source_text}
-          MARKDOWN
-
-          markdown.render(source_text_with_heading)
-        end
-    end
-
-    def title
-      metadata["title"]
-    end
-
-    def title_suffix
-      metadata["home"] ? "" : " - Administrate"
-    end
-
-    private
-
-    attr_reader :source_text, :metadata
-  end
 end

spec/example_app/app/models/doc_page.rb

@@ -0,0 +1,69 @@
+class DocPage
+  REDCARPET_CONFIG = {
+    fenced_code_blocks: true,
+    autolink: true,
+  }.freeze
+
+  class << self
+    def find(page)
+      full_path = Rails.root + "../../#{page}.md"
+
+      if File.exist?(full_path)
+        text = File.read(full_path)
+        new(text)
+      end
+    end
+  end
+
+  def initialize(text)
+    @text = text
+  end
+
+  def title
+    document.title
+  end
+
+  def body
+    document.body
+  end
+
+  private
+
+  attr_reader :text
+
+  def document
+    @document ||= DocumentParser.new(text)
+  end
+
+  class DocumentParser
+    def initialize(source_text)
+      parsed_document = FrontMatterParser::Parser.new(:md).call(source_text)
+      @source_text = parsed_document.content
+      @metadata = parsed_document.front_matter
+    end
+
+    def body
+      @body ||=
+        begin
+          renderer = Redcarpet::Render::HTML
+          markdown = Redcarpet::Markdown.new(renderer, REDCARPET_CONFIG)
+
+          source_text_with_heading = <<~MARKDOWN
+            # #{title}
+
+            #{source_text}
+          MARKDOWN
+
+          markdown.render(source_text_with_heading)
+        end
+    end
+
+    def title
+      metadata["title"]
+    end
+
+    private
+
+    attr_reader :source_text, :metadata
+  end
+end

spec/features/documentation_spec.rb

@@ -7,6 +7,31 @@
     expect(page).to have_http_status(:not_found)
   end
 
+  it "shows the README" do
+    visit(root_path)
+
+    expect(page).to have_css("h1", text: "Administrate")
+    expect(page).to have_content(
+      "A framework for creating flexible, powerful admin dashboards in Rails",
+    )
+  end
+
+  it "shows the Contributing Guides" do
+    visit("/contributing")
+
+    expect(page).to have_css("h1", text: "Contributing Guide")
+    expect(page).to have_content(
+      "We welcome pull requests from everyone.",
+    )
+  end
+
+  it "shows other docs pages" do
+    visit("/getting_started")
+
+    expect(page).to have_css("h1", text: "Getting Started")
+    expect(page).to have_content("Administrate is released as a Ruby gem")
+  end
+
   it "links to each documentation page" do
     visit root_path
     links = internal_documentation_links
@@ -19,7 +44,7 @@
     end
   end
 
-  it "links to the Github repo" do
+  it "links to the GitHub repo" do
     visit root_path
 
     expect(github_link[:href]).

spec/models/doc_page_spec.rb

@@ -0,0 +1,34 @@
+require "rails_helper"
+
+RSpec.describe DocPage do
+  describe ".find" do
+    it "is nil if the page doesn't exist" do
+      page = DocPage.find("not_a_page")
+
+      expect(page).to be_nil
+    end
+
+    it "renders pages without metadata" do
+      page = DocPage.find("README")
+
+      expect(page).to have_attributes(
+        title: nil,
+        body: a_string_matching(
+          /A framework for creating flexible, powerful admin dashboards/
+        ),
+      )
+    end
+
+    it "renders pages with metadata" do
+      page = DocPage.find("docs/getting_started")
+
+      expect(page).to have_attributes(
+        title: "Getting Started",
+        body: a_string_starting_with(
+          "<h1>Getting Started</h1>\n\n<p>Administrate is released as a Ruby gem"
+        ),
+      )
+    end
+
+  end
+end