Remove canonical-rails gem and handroll our own

Gemfile

@@ -20,9 +20,6 @@ gem 'puma', '~> 6.5'
 # Reduces boot times through caching; required in config/boot.rb
 gem 'bootsnap', '>= 1.1.0', require: false
 
-# Canonical meta tag
-gem 'canonical-rails'
-
 # Decorate logic to keep it out of the views and helper methods
 gem 'draper'
 

Gemfile.lock

@@ -177,8 +177,6 @@ GEM
       activesupport (>= 3.0.0)
       uniform_notifier (~> 1.11)
     byebug (11.1.3)
-    canonical-rails (0.2.16)
-      actionview (>= 4.1, < 7.3)
     capybara (3.40.0)
       addressable
       matrix
@@ -756,7 +754,6 @@ DEPENDENCIES
   brakeman
   bullet
   byebug
-  canonical-rails
   capybara (>= 2.15)
   cloudfront-rails
   colorize

app/views/layouts/application.html.erb

@@ -4,7 +4,11 @@
     <title><%= yield :page_title %> - Publish teacher training courses - GOV.UK</title>
     <%= csrf_meta_tags %>
     <%= csp_meta_tag %>
-    <%= canonical_tag %>
+
+    <% canonical_url = "#{request.base_url}#{request.path.chomp('/')}/" %>
+
+    <%= tag.link(href: canonical_url, rel: "canonical") %>
+    <%= tag.meta(property: "og:url", content: canonical_url) %>
 
     <%= tag.meta(name: "viewport", content: "width=device-width, initial-scale=1") %>
     <%= tag.meta(property: "og:image", content: image_path("govuk-opengraph-image.png")) %>

app/views/layouts/find_layout.html.erb

@@ -4,7 +4,11 @@
     <title><%= yield :page_title %> - <%= t("service_name.find") %> - GOV.UK</title>
     <%= csrf_meta_tags %>
     <%= csp_meta_tag %>
-    <%= canonical_tag %>
+
+    <% canonical_url = "#{request.base_url}#{request.path.chomp('/')}/" %>
+
+    <%= tag.link(href: canonical_url, rel: "canonical") %>
+    <%= tag.meta(property: "og:url", content: canonical_url) %>
 
     <%= tag.meta(name: "viewport", content: "width=device-width, initial-scale=1") %>
     <%= tag.meta(property: "og:image", content: image_path("govuk-opengraph-image.png")) %>

spec/features/canonical_tags_spec.rb

@@ -0,0 +1,93 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+feature 'Canonical tags', :with_find_constraint do
+  before do
+    given_i_have_courses
+    and_i_visit_the_home_page
+  end
+
+  describe 'Canonical tags on Find pages' do
+    scenario 'without query params' do
+      then_the_page_contains_canonical_tags_with_no_query_params
+    end
+
+    scenario 'with query parameters' do
+      and_i_select_the_across_england_radio_button
+      then_the_page_contains_canonical_tags_without_query_params
+    end
+
+    scenario 'when visiting a course' do
+      when_i_visit_the_course_page
+      then_the_page_contains_canonical_tags_for_a_course
+    end
+
+    scenario 'when visiting a course and selecting an anchor tag' do
+      when_i_visit_the_course_page
+      and_i_click_an_anchor_tag
+      then_the_page_contains_canonical_tags_for_a_course
+    end
+  end
+
+  describe 'Canonical tags on Publish pages', :with_publish_constraint do
+    scenario 'Publish page contains canonical tags' do
+      and_i_visit_the_publish_page
+      then_the_publish_page_contains_canonical_tags
+    end
+  end
+
+  def when_i_visit_the_course_page
+    visit find_course_path(
+      provider_code: @mathematics_course.provider.provider_code,
+      course_code: @mathematics_course.course_code
+    )
+  end
+
+  def given_i_have_courses
+    provider = create(:provider)
+    @mathematics_course = create(:course, :published_postgraduate, :secondary, provider:, name: 'Mathematics', subjects: [find_or_create(:secondary_subject, :mathematics)])
+  end
+
+  def and_i_visit_the_home_page
+    visit '/'
+  end
+
+  def and_i_visit_the_publish_page
+    visit '/sign-in/'
+  end
+
+  def and_i_select_the_across_england_radio_button
+    choose 'Across England'
+    click_link_or_button 'Continue'
+  end
+
+  def and_i_click_an_anchor_tag
+    click_link_or_button 'Where you will train'
+  end
+
+  def then_the_page_contains_canonical_tags_for_a_course
+    canonical_url = "http://www.example.com/course/#{@mathematics_course.provider.provider_code}/#{@mathematics_course.course_code}/"
+
+    link_tag = page.find("link[rel='canonical']", visible: :all)
+    expect(link_tag[:href]).to eq(canonical_url)
+
+    og_url_tag = page.find("meta[property='og:url']", visible: :all)
+    expect(og_url_tag[:content]).to eq(canonical_url)
+  end
+
+  def then_the_page_contains_canonical_tags_with_no_query_params
+    expect(page).to have_css("link[rel='canonical'][href='http://www.example.com/']", visible: :all)
+    expect(page).to have_css("meta[property='og:url'][content='http://www.example.com/']", visible: :all)
+  end
+
+  def then_the_page_contains_canonical_tags_without_query_params
+    expect(page).to have_css("link[rel='canonical'][href='http://www.example.com/age-groups/']", visible: :all)
+    expect(page).to have_css("meta[property='og:url'][content='http://www.example.com/age-groups/']", visible: :all)
+  end
+
+  def then_the_publish_page_contains_canonical_tags
+    expect(page).to have_css("link[rel='canonical'][href='http://www.example.com/sign-in/']", visible: :all)
+    expect(page).to have_css("meta[property='og:url'][content='http://www.example.com/sign-in/']", visible: :all)
+  end
+end