Add support for defining custom url helpers in routes.rb

Allow the definition of custom url helpers that will be available
automatically wherever standard url helpers are available. The
current solution is to create helper methods in ApplicationHelper
or some other helper module and this isn't a great solution since
the url helper module can be called directly or included in another
class which doesn't include the normal helper modules.

Reference rails#22512.

Author: pixeltrix

actionpack/lib/action_dispatch/routing/mapper.rb

@@ -2015,6 +2015,46 @@ def concerns(*args)
         end
       end
 
+      module UrlHelpers
+        # Define a custom url helper that will be added to the url helpers
+        # module. This allows you override and/or replace the default behavior
+        # of routing helpers, e.g:
+        #
+        #   url_helper :homepage do
+        #     "http://www.rubyonrails.org"
+        #   end
+        #
+        #   url_helper :commentable do |model|
+        #     [ model, anchor: model.dom_id ]
+        #   end
+        #
+        #   url_helper :main do
+        #     { controller: 'pages', action: 'index', subdomain: 'www' }
+        #   end
+        #
+        # The return value must be a valid set of arguments for `url_for` which
+        # will actually build the url string. This can be one of the following:
+        #
+        #   * A string, which is treated as a generated url
+        #   * A hash, e.g. { controller: 'pages', action: 'index' }
+        #   * An array, which is passed to `polymorphic_url`
+        #   * An Active Model instance
+        #   * An Active Model class
+        #
+        # You can also specify default options that will be passed through to
+        # your url helper definition, e.g:
+        #
+        #   url_helper :browse, page: 1, size: 10 do |options|
+        #     [ :products, options.merge(params.permit(:page, :size)) ]
+        #   end
+        #
+        # NOTE: It is the url helper's responsibility to return the correct
+        # set of options to be passed to the `url_for` call.
+        def url_helper(name, options = {}, &block)
+          @set.add_url_helper(name, options, &block)
+        end
+      end
+
       class Scope # :nodoc:
         OPTIONS = [:path, :shallow_path, :as, :shallow_prefix, :module,
                    :controller, :action, :path_names, :constraints,
@@ -2109,6 +2149,7 @@ def initialize(set) #:nodoc:
       include Scoping
       include Concerns
       include Resources
+      include UrlHelpers
     end
   end
 end

actionpack/lib/action_dispatch/routing/route_set.rb

@@ -74,6 +74,7 @@ def initialize
           @routes  = {}
           @path_helpers = Set.new
           @url_helpers = Set.new
+          @custom_helpers = Set.new
           @url_helpers_module  = Module.new
           @path_helpers_module = Module.new
         end
@@ -96,9 +97,23 @@ def clear!
             @url_helpers_module.send  :undef_method, helper
           end
 
+          @custom_helpers.each do |helper|
+            path_name = :"#{helper}_path"
+            url_name = :"#{helper}_url"
+
+            if @path_helpers_module.method_defined?(path_name)
+              @path_helpers_module.send :undef_method, path_name
+            end
+
+            if @url_helpers_module.method_defined?(url_name)
+              @url_helpers_module.send :undef_method, url_name
+            end
+          end
+
           @routes.clear
           @path_helpers.clear
           @url_helpers.clear
+          @custom_helpers.clear
         end
 
         def add(name, route)
@@ -144,6 +159,62 @@ def length
           routes.length
         end
 
+        def add_url_helper(name, defaults, &block)
+          @custom_helpers << name
+          helper = CustomUrlHelper.new(name, defaults, &block)
+
+          @path_helpers_module.module_eval do
+            define_method(:"#{name}_path") do |*args|
+              options = args.extract_options!
+              helper.call(self, args, options, only_path: true)
+            end
+          end
+
+          @url_helpers_module.module_eval do
+            define_method(:"#{name}_url") do |*args|
+              options = args.extract_options!
+              helper.call(self, args, options)
+            end
+          end
+        end
+
+        class CustomUrlHelper
+          attr_reader :name, :defaults, :block
+
+          def initialize(name, defaults, &block)
+            @name = name
+            @defaults = defaults
+            @block = block
+          end
+
+          def call(t, args, options, outer_options = {})
+            url_options = eval_block(t, args, options)
+
+            case url_options
+            when String
+              t.url_for(url_options)
+            when Hash
+              t.url_for(url_options.merge(outer_options))
+            when ActionController::Parameters
+              if url_options.permitted?
+                t.url_for(url_options.to_h.merge(outer_options))
+              else
+                raise ArgumentError, "Generating an URL from non sanitized request parameters is insecure!"
+              end
+            when Array
+              opts = url_options.extract_options!
+              t.url_for(url_options.push(opts.merge(outer_options)))
+            else
+              t.url_for([url_options, outer_options])
+            end
+          end
+
+          private
+            def eval_block(t, args, options)
+              t.instance_exec(*args, defaults.merge(options), &block)
+            end
+        end
+
         class UrlHelper
           def self.create(route, options, route_name, url_strategy)
             if optimize_helper?(route)
@@ -533,6 +604,10 @@ def add_route(mapping, path_ast, name, anchor)
         route
       end
 
+      def add_url_helper(name, options, &block)
+        named_routes.add_url_helper(name, options, &block)
+      end
+
       class Generator
         PARAMETERIZE = lambda do |name, value|
           if name == :controller

actionpack/test/dispatch/routing/custom_url_helpers_test.rb

@@ -0,0 +1,121 @@
+require 'abstract_unit'
+
+class TestCustomUrlHelpers < ActionDispatch::IntegrationTest
+  class Linkable
+    attr_reader :id
+
+    def initialize(id)
+      @id = id
+    end
+
+    def linkable_type
+      self.class.name.demodulize.underscore
+    end
+  end
+
+  class Category < Linkable; end
+  class Collection < Linkable; end
+  class Product < Linkable; end
+
+  Routes = ActionDispatch::Routing::RouteSet.new
+  Routes.draw do
+    default_url_options host: 'www.example.com'
+
+    root to: 'pages#index'
+    get '/basket', to: 'basket#show', as: :basket
+
+    resources :categories, :collections, :products
+
+    namespace :admin do
+      get '/dashboard', to: 'dashboard#index'
+    end
+
+    url_helper(:website)  { "http://www.rubyonrails.org" }
+    url_helper(:linkable) { |linkable| [:"#{linkable.linkable_type}", { id: linkable.id }] }
+    url_helper(:params)   { |params| params }
+    url_helper(:symbol)   { :basket }
+    url_helper(:hash)     { { controller: "basket", action: "show" } }
+    url_helper(:array)    { [:admin, :dashboard] }
+    url_helper(:options)  { |options| [:products, options] }
+    url_helper(:defaults, size: 10) { |options| [:products, options] }
+  end
+
+  APP = build_app Routes
+
+  def app
+    APP
+  end
+
+  include Routes.url_helpers
+
+  def setup
+    @category = Category.new("1")
+    @collection = Collection.new("2")
+    @product = Product.new("3")
+    @path_params = { 'controller' => 'pages', 'action' => 'index' }
+    @unsafe_params = ActionController::Parameters.new(@path_params)
+    @safe_params = ActionController::Parameters.new(@path_params).permit(:controller, :action)
+  end
+
+  def test_custom_path_helper
+    assert_equal "http://www.rubyonrails.org", website_path
+    assert_equal "http://www.rubyonrails.org", Routes.url_helpers.website_path
+
+    assert_equal "/categories/1", linkable_path(@category)
+    assert_equal "/categories/1", Routes.url_helpers.linkable_path(@category)
+    assert_equal "/collections/2", linkable_path(@collection)
+    assert_equal "/collections/2", Routes.url_helpers.linkable_path(@collection)
+    assert_equal "/products/3", linkable_path(@product)
+    assert_equal "/products/3", Routes.url_helpers.linkable_path(@product)
+
+    assert_equal "/", params_path(@safe_params)
+    assert_equal "/", Routes.url_helpers.params_path(@safe_params)
+    assert_raises(ArgumentError) { params_path(@unsafe_params) }
+    assert_raises(ArgumentError) { Routes.url_helpers.params_path(@unsafe_params) }
+
+    assert_equal "/basket", symbol_path
+    assert_equal "/basket", Routes.url_helpers.symbol_path
+    assert_equal "/basket", hash_path
+    assert_equal "/basket", Routes.url_helpers.hash_path
+    assert_equal "/admin/dashboard", array_path
+    assert_equal "/admin/dashboard", Routes.url_helpers.array_path
+
+    assert_equal "/products?page=2", options_path(page: 2)
+    assert_equal "/products?page=2", Routes.url_helpers.options_path(page: 2)
+    assert_equal "/products?size=10", defaults_path
+    assert_equal "/products?size=10", Routes.url_helpers.defaults_path
+    assert_equal "/products?size=20", defaults_path(size: 20)
+    assert_equal "/products?size=20", Routes.url_helpers.defaults_path(size: 20)
+  end
+
+  def test_custom_url_helper
+    assert_equal "http://www.rubyonrails.org", website_url
+    assert_equal "http://www.rubyonrails.org", Routes.url_helpers.website_url
+
+    assert_equal "http://www.example.com/categories/1", linkable_url(@category)
+    assert_equal "http://www.example.com/categories/1", Routes.url_helpers.linkable_url(@category)
+    assert_equal "http://www.example.com/collections/2", linkable_url(@collection)
+    assert_equal "http://www.example.com/collections/2", Routes.url_helpers.linkable_url(@collection)
+    assert_equal "http://www.example.com/products/3", linkable_url(@product)
+    assert_equal "http://www.example.com/products/3", Routes.url_helpers.linkable_url(@product)
+
+    assert_equal "http://www.example.com/", params_url(@safe_params)
+    assert_equal "http://www.example.com/", Routes.url_helpers.params_url(@safe_params)
+    assert_raises(ArgumentError) { params_url(@unsafe_params) }
+    assert_raises(ArgumentError) { Routes.url_helpers.params_url(@unsafe_params) }
+
+    assert_equal "http://www.example.com/basket", symbol_url
+    assert_equal "http://www.example.com/basket", Routes.url_helpers.symbol_url
+    assert_equal "http://www.example.com/basket", hash_url
+    assert_equal "http://www.example.com/basket", Routes.url_helpers.hash_url
+    assert_equal "/admin/dashboard", array_path
+    assert_equal "/admin/dashboard", Routes.url_helpers.array_path
+
+    assert_equal "http://www.example.com/products?page=2", options_url(page: 2)
+    assert_equal "http://www.example.com/products?page=2", Routes.url_helpers.options_url(page: 2)
+    assert_equal "http://www.example.com/products?size=10", defaults_url
+    assert_equal "http://www.example.com/products?size=10", Routes.url_helpers.defaults_url
+    assert_equal "http://www.example.com/products?size=20", defaults_url(size: 20)
+    assert_equal "http://www.example.com/products?size=20", Routes.url_helpers.defaults_url(size: 20)
+  end
+end

railties/test/application/routing_test.rb

@@ -245,7 +245,10 @@ def index
       assert_equal 'WIN', last_response.body
     end
 
-    {"development" => "baz", "production" => "bar"}.each do |mode, expected|
+    {
+      "development" => ["baz", "http://www.apple.com"],
+      "production"  => ["bar", "http://www.microsoft.com" ]
+    }.each do |mode, (expected_action, expected_url)|
       test "reloads routes when configuration is changed in #{mode}" do
         controller :foo, <<-RUBY
           class FooController < ApplicationController
@@ -256,12 +259,19 @@ def bar
             def baz
               render text: "baz"
             end
+
+            def custom
+              render text: custom_url
+            end
           end
         RUBY
 
         app_file 'config/routes.rb', <<-RUBY
           Rails.application.routes.draw do
             get 'foo', to: 'foo#bar'
+            get 'custom', to: 'foo#custom'
+
+            url_helper(:custom) { "http://www.microsoft.com" }
           end
         RUBY
 
@@ -270,16 +280,25 @@ def baz
         get '/foo'
         assert_equal 'bar', last_response.body
 
+        get '/custom'
+        assert_equal 'http://www.microsoft.com', last_response.body
+
         app_file 'config/routes.rb', <<-RUBY
           Rails.application.routes.draw do
             get 'foo', to: 'foo#baz'
+            get 'custom', to: 'foo#custom'
+
+            url_helper(:custom) { "http://www.apple.com" }
           end
         RUBY
 
         sleep 0.1
 
         get '/foo'
-        assert_equal expected, last_response.body
+        assert_equal expected_action, last_response.body
+
+        get '/custom'
+        assert_equal expected_url, last_response.body
       end
     end
 
@@ -340,6 +359,10 @@ class FooController < ApplicationController
           def index
             render text: "foo"
           end
+
+          def custom
+            render text: custom_url
+          end
         end
       RUBY
 
@@ -425,16 +448,19 @@ def index
       app_file 'config/routes.rb', <<-RUBY
         Rails.application.routes.draw do
           get ':locale/foo', to: 'foo#index', as: 'foo'
+          url_helper(:microsoft) { 'http://www.microsoft.com' }
         end
       RUBY
 
       get '/en/foo'
       assert_equal 'foo', last_response.body
       assert_equal '/en/foo', Rails.application.routes.url_helpers.foo_path(:locale => 'en')
+      assert_equal 'http://www.microsoft.com', Rails.application.routes.url_helpers.microsoft_url
 
       app_file 'config/routes.rb', <<-RUBY
         Rails.application.routes.draw do
           get ':locale/bar', to: 'bar#index', as: 'foo'
+          url_helper(:apple) { 'http://www.apple.com' }
         end
       RUBY
 
@@ -446,6 +472,11 @@ def index
       get '/en/bar'
       assert_equal 'bar', last_response.body
       assert_equal '/en/bar', Rails.application.routes.url_helpers.foo_path(:locale => 'en')
+      assert_equal 'http://www.apple.com', Rails.application.routes.url_helpers.apple_url
+
+      assert_raises NoMethodError do
+        assert_equal 'http://www.microsoft.com', Rails.application.routes.url_helpers.microsoft_url
+      end
     end
 
     test 'resource routing with irregular inflection' do