Allow url_for to infer the name of the link from Model#to_s

Author: olivierlacan

actionview/CHANGELOG.md

@@ -1,3 +1,26 @@
+*   Allow `link_to` helper to infer link name from `Model#to_s` when it 
+    is used with a single argument:
+
+        link_to @profile
+        #=> <a href="/profiles/1">Eileen</a>
+
+    This assumes the model class implements a `to_s` method like this: 
+
+        class Profile < ApplicationRecord 
+          # ...
+          def to_s
+            name
+          end
+        end
+
+    Previously you had to supply a second argument even if the `Profile`
+    model implemented a `#to_s` method that called the `name` method.
+
+        link_to @profile, @profile.name
+        #=> <a href="/profiles/1">Eileen</a>
+
+    *Olivier Lacan*
+
 *   Add `weekday_options_for_select` and `weekday_select` helper methods. Also adds `weekday_select` to `FormBuilder`.
 
     *Drew Bragg*, *Dana Kashubeck*, *Kasper Timm Hansen*

actionview/lib/action_view/helpers/url_helper.rb

@@ -85,6 +85,8 @@ def _filtered_referrer # :nodoc:
       #     # name
       #   end
       #
+      #   link_to(active_record_model)
+      #
       # ==== Options
       # * <tt>:data</tt> - This option can be used to add custom data attributes.
       # * <tt>method: symbol of HTTP verb</tt> - This modifier will dynamically
@@ -146,6 +148,12 @@ def _filtered_referrer # :nodoc:
       #   link_to nil, "http://example.com"
       #   # => <a href="http://www.example.com">http://www.example.com</a>
       #
+      # More concise yet, when +name+ is an ActiveRecord model that defines a
+      # +to_s+ method returning a default value or a model instance attribute
+      #
+      #   link_to @profile
+      #   # => <a href="http://www.example.com/profiles/1">Eileen</a>
+      #
       # You can use a block as well if your link target is hard to fit into the name parameter. ERB example:
       #
       #   <%= link_to(@profile) do %>
@@ -201,7 +209,7 @@ def link_to(name = nil, options = nil, html_options = nil, &block)
 
         html_options = convert_options_to_data_attributes(options, html_options)
 
-        url = url_for(options)
+        url = url_target(name, options)
         html_options["href"] ||= url
 
         content_tag("a", name || url, html_options, &block)
@@ -716,6 +724,14 @@ def convert_options_to_data_attributes(options, html_options)
           end
         end
 
+        def url_target(name, options)
+          if name.respond_to?(:model_name) && options.empty?
+            url_for(name)
+          else
+            url_for(options)
+          end
+        end
+
         def link_to_remote_options?(options)
           if options.is_a?(Hash)
             options.delete("remote") || options.delete(:remote)

actionview/test/template/url_helper_test.rb

@@ -35,6 +35,7 @@ class UrlHelperTest < ActiveSupport::TestCase
     get "/other" => "foo#other"
     get "/article/:id" => "foo#article", :as => :article
     get "/category/:category" => "foo#category"
+    resources :workshops
 
     scope :engine do
       get "/" => "foo#bar"
@@ -511,6 +512,12 @@ def test_link_tag_does_not_escape_html_safe_content
       link_to(raw("Malicious <script>content</script>"), "/")
   end
 
+  def test_link_tag_using_active_record_model
+    @workshop = Workshop.new(1.to_s)
+    link = link_to(@workshop)
+    assert_dom_equal %{<a href="/workshops/1">1</a>}, link
+  end
+
   def test_link_to_unless
     assert_equal "Showing", link_to_unless(true, "Showing", url_hash)