Add allow_browser to set minimum versions for your application

Gemfile

@@ -94,6 +94,7 @@ else
 end
 
 gem "kredis", ">= 1.7.0", require: false
+gem "useragent", require: false
 
 # Active Job
 group :job do

Gemfile.lock

@@ -56,6 +56,7 @@ PATH
       rack-test (>= 0.6.3)
       rails-dom-testing (~> 2.2)
       rails-html-sanitizer (~> 1.6)
+      useragent (~> 0.16)
     actiontext (7.2.0.alpha)
       actionpack (= 7.2.0.alpha)
       activerecord (= 7.2.0.alpha)
@@ -191,8 +192,6 @@ GEM
       railties (>= 6.0.0)
     date (3.3.3)
     debug (1.7.1)
-      irb (>= 1.5.0)
-      reline (>= 0.3.1)
     declarative (0.0.20)
     delayed_job (4.1.11)
       activesupport (>= 3.0, < 8.0)
@@ -545,6 +544,7 @@ GEM
       concurrent-ruby (~> 1.0)
     uber (0.1.0)
     unicode-display_width (2.5.0)
+    useragent (0.16.10)
     w3c_validators (1.3.7)
       json (>= 1.8)
       nokogiri (~> 1.6)
@@ -648,6 +648,7 @@ DEPENDENCIES
   trilogy (>= 2.5.0)
   turbo-rails
   tzinfo-data
+  useragent
   w3c_validators (~> 1.3.6)
   wdm (>= 0.1.0)
   web-console

actionpack/actionpack.gemspec

@@ -42,6 +42,7 @@ Gem::Specification.new do |s|
   s.add_dependency "rack-test", ">= 0.6.3"
   s.add_dependency "rails-html-sanitizer", "~> 1.6"
   s.add_dependency "rails-dom-testing", "~> 2.2"
+  s.add_dependency "useragent", "~> 0.16"
   s.add_dependency "actionview", version
 
   s.add_development_dependency "activemodel", version

actionpack/lib/action_controller.rb

@@ -27,6 +27,7 @@ module ActionController
   end
 
   autoload_under "metal" do
+    autoload :AllowBrowser
     autoload :ConditionalGet
     autoload :ContentSecurityPolicy
     autoload :Cookies

actionpack/lib/action_controller/base.rb

@@ -215,6 +215,7 @@ def self.without_modules(*modules)
       ContentSecurityPolicy,
       PermissionsPolicy,
       RateLimiting,
+      AllowBrowser,
       Streaming,
       DataStreaming,
       HttpAuthentication::Basic::ControllerMethods,

actionpack/lib/action_controller/metal/allow_browser.rb

@@ -0,0 +1,111 @@
+# frozen_string_literal: true
+
+module ActionController # :nodoc:
+  module AllowBrowser
+    extend ActiveSupport::Concern
+
+    module ClassMethods
+      # Specify the browser versions that will be allowed to access all actions (or some, as limited by <tt>only:</tt> or <tt>except:</tt>).
+      # Only browsers matched in the hash or named set passed to <tt>versions:</tt> will be blocked if they're below the versions specified.
+      # This means that all other browsers, as well as agents that aren't reporting a user-agent header, will be allowed access.
+      #
+      # A browser that's blocked will by default be served the file in public/426.html with a HTTP status code of "426 Upgrade Required".
+      #
+      # In addition to specifically named browser versions, you can also pass <tt>:modern</tt> as the set to restrict support to browsers
+      # natively supporting webp images, web push, badges, import maps, CSS nesting, and CSS :has.
+      # This includes Safari 17.2+, Chrome 119+, Firefox 121+, Opera 104+.
+      #
+      # You can use https://caniuse.com to check for browser versions supporting the features you use.
+      #
+      # You can use +ActiveSupport::Notifications+ to subscribe to events of browsers being blocked using the +browser_block.action_controller+
+      # event name.
+      #
+      # Examples:
+      #
+      #   class ApplicationController < ActionController::Base
+      #     # Allow only browsers natively supporting webp images, web push, badges, import maps, CSS nesting + :has
+      #     allow_browser versions: :modern
+      #   end
+      #
+      #   class ApplicationController < ActionController::Base
+      #     # All versions of Chrome and Opera will be allowed, but no versions of "internet explorer" (ie). Safari needs to be 16.4+ and Firefox 121+.
+      #     allow_browser versions: { safari: 16.4, firefox: 121, ie: false }
+      #   end
+      #
+      #   class MessagesController < ApplicationController
+      #     # In addition to the browsers blocked by ApplicationController, also block Opera below 104 and Chrome below 119 for the show action.
+      #     allow_browser versions: { opera: 104, chrome: 119 }, only: :show
+      #   end
+      def allow_browser(versions:, block: -> { render file: Rails.root.join("public/426.html"), layout: false, status: :upgrade_required }, **options)
+        before_action -> { allow_browser(versions: versions, block: block) }, **options
+      end
+    end
+
+    private
+      def allow_browser(versions:, block:)
+        require "useragent"
+
+        if BrowserBlocker.new(request, versions: versions).blocked?
+          ActiveSupport::Notifications.instrument("browser_block.action_controller", request: request, versions: versions) do
+            instance_exec(&block)
+          end
+        end
+      end
+
+      class BrowserBlocker
+        SETS = {
+          modern: { safari: 17.2, chrome: 119, firefox: 121, opera: 104, ie: false }
+        }
+
+        attr_reader :request, :versions
+
+        def initialize(request, versions:)
+          @request, @versions = request, versions
+        end
+
+        def blocked?
+          user_agent_version_reported? && unsupported_browser?
+        end
+
+        private
+          def parsed_user_agent
+            @parsed_user_agent ||= UserAgent.parse(request.user_agent)
+          end
+
+          def user_agent_version_reported?
+            request.user_agent.present? && parsed_user_agent.version.to_s.present?
+          end
+
+          def unsupported_browser?
+            version_guarded_browser? && version_below_minimum_required?
+          end
+
+          def version_guarded_browser?
+            minimum_browser_version_for_browser != nil
+          end
+
+          def version_below_minimum_required?
+            if minimum_browser_version_for_browser
+              parsed_user_agent.version < UserAgent::Version.new(minimum_browser_version_for_browser.to_s)
+            else
+              true
+            end
+          end
+
+          def minimum_browser_version_for_browser
+            expanded_versions[normalized_browser_name]
+          end
+
+          def expanded_versions
+            @expanded_versions ||= (SETS[versions] || versions).with_indifferent_access
+          end
+
+          def normalized_browser_name
+            case name = parsed_user_agent.browser.downcase
+            when "internet explorer" then "ie"
+            else name
+            end
+          end
+      end
+  end
+end

actionpack/test/controller/allow_browser_test.rb

@@ -0,0 +1,67 @@
+# frozen_string_literal: true
+
+require "abstract_unit"
+
+class AllowBrowserController < ActionController::Base
+  allow_browser versions: { safari: "16.4", chrome: "119", firefox: "123", opera: "104", ie: false }, block: -> { head :upgrade_required }, only: :hello
+  def hello
+    head :ok
+  end
+
+  allow_browser versions: :modern, block: -> { head :upgrade_required }, only: :modern
+  def modern
+    head :ok
+  end
+end
+
+class AllowBrowserTest < ActionController::TestCase
+  tests AllowBrowserController
+
+  CHROME_118    = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/118 Safari/537.36"
+  CHROME_120    = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120 Safari/537.36"
+  SAFARI_17_2_0 = "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.2.0 Safari/605.1.15"
+  FIREFOX_114   = "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:109.0) Gecko/20100101 Firefox/114.0"
+  IE_11         = "Mozilla/5.0 (Windows NT 10.0; WOW64; Trident/7.0; rv:11.0) like Gecko"
+  OPERA_104     = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/95.0.4638.69 Safari/537.36 OPR/104.0.4638.54"
+
+  test "blocked browser below version limit" do
+    get_with_agent :hello, FIREFOX_114
+    assert_response :upgrade_required
+  end
+
+  test "blocked browser by name" do
+    get_with_agent :hello, IE_11
+    assert_response :upgrade_required
+  end
+
+  test "allowed browsers above specific version limit" do
+    get_with_agent :hello, SAFARI_17_2_0
+    assert_response :ok
+
+    get_with_agent :hello, CHROME_120
+    assert_response :ok
+
+    get_with_agent :hello, OPERA_104
+    assert_response :ok
+  end
+
+  test "browsers against modern limit" do
+    get_with_agent :modern, SAFARI_17_2_0
+    assert_response :ok
+
+    get_with_agent :modern, CHROME_118
+    assert_response :upgrade_required
+
+    get_with_agent :modern, CHROME_120
+    assert_response :ok
+
+    get_with_agent :modern, OPERA_104
+    assert_response :ok
+  end
+
+  private
+    def get_with_agent(action, agent)
+      @request.headers["User-Agent"] = agent
+      get action
+    end
+end

railties/lib/rails/generators/rails/app/app_generator.rb

@@ -475,6 +475,7 @@ def delete_public_files_if_api_option
         if options[:api]
           remove_file "public/404.html"
           remove_file "public/422.html"
+          remove_file "public/426.html"
           remove_file "public/500.html"
           remove_file "public/apple-touch-icon-precomposed.png"
           remove_file "public/apple-touch-icon.png"

railties/lib/rails/generators/rails/app/templates/app/controllers/application_controller.rb.tt

@@ -1,2 +1,6 @@
 class ApplicationController < ActionController::<%= options.api? ? "API" : "Base" %>
+<%- unless options.api? -%>
+  # Only allow modern browsers supporting webp images, web push, badges, import maps, CSS nesting, and CSS :has.
+  allow_browser versions: :modern
+<% end -%>
 end

railties/lib/rails/generators/rails/app/templates/public/426.html

@@ -0,0 +1,66 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <title>Your browser is not supported (426)</title>
+  <meta name="viewport" content="width=device-width,initial-scale=1">
+  <style>
+  .rails-default-error-page {
+    background-color: #EFEFEF;
+    color: #2E2F30;
+    text-align: center;
+    font-family: arial, sans-serif;
+    margin: 0;
+  }
+
+  .rails-default-error-page div.dialog {
+    width: 95%;
+    max-width: 33em;
+    margin: 4em auto 0;
+  }
+
+  .rails-default-error-page div.dialog > div {
+    border: 1px solid #CCC;
+    border-right-color: #999;
+    border-left-color: #999;
+    border-bottom-color: #BBB;
+    border-top: #B00100 solid 4px;
+    border-top-left-radius: 9px;
+    border-top-right-radius: 9px;
+    background-color: white;
+    padding: 7px 12% 0;
+    box-shadow: 0 3px 8px rgba(50, 50, 50, 0.17);
+  }
+
+  .rails-default-error-page h1 {
+    font-size: 100%;
+    color: #730E15;
+    line-height: 1.5em;
+  }
+
+  .rails-default-error-page div.dialog > p {
+    margin: 0 0 1em;
+    padding: 1em;
+    background-color: #F7F7F7;
+    border: 1px solid #CCC;
+    border-right-color: #999;
+    border-left-color: #999;
+    border-bottom-color: #999;
+    border-bottom-left-radius: 4px;
+    border-bottom-right-radius: 4px;
+    border-top-color: #DADADA;
+    color: #666;
+    box-shadow: 0 3px 8px rgba(50, 50, 50, 0.17);
+  }
+  </style>
+</head>
+
+<body class="rails-default-error-page">
+  <!-- This file lives in public/426.html -->
+  <div class="dialog">
+    <div>
+      <h1>Your browser is not supported.</h1>
+      <p>Please upgrade your browser to continue.</p>
+    </div>
+  </div>
+</body>
+</html>

railties/test/application/rake_test.rb

@@ -182,7 +182,7 @@ class Hello
     end
 
     def test_code_statistics
-      assert_match "Code LOC: 62     Test LOC: 5     Code to Test Ratio: 1:0.1",
+      assert_match "Code LOC: 63     Test LOC: 5     Code to Test Ratio: 1:0.1",
         rails("stats")
     end
 

railties/test/generators/api_app_generator_test.rb

@@ -180,6 +180,7 @@ def skipped_files
          tmp/cache/assets
          public/404.html
          public/422.html
+         public/426.html
          public/500.html
          public/apple-touch-icon-precomposed.png
          public/apple-touch-icon.png