Singleton: Inline find_singleton back into find

When the Singleton module was originally introduced in [#4][], there was
a suggestion about the implementation for `.find` that used the `:one`
modifier option with the `:from` keyword argument.

```ruby
class Account < ActiveResource::Base
  def self.find_singleton
    find :one, from: '/account.xml'
  end
end
```

This commit modifies the `Singleton.find` method by inlining the private
`find_singleton` method. By doing so, the implementation can invoke
`super`, and rely on the built-in `instantiate_record` call provided by
`Base`.

This reduces the amount of duplication involved in transforming a
response payload into a resource instance.

[#4]: #4
[#4]: #4 (comment)

Author: seanpdoyle

lib/active_resource/base.rb

@@ -1217,12 +1217,14 @@ def find_every(options)
 
         # Find a single resource from a one-off URL
         def find_one(options)
+          prefix_options, query_options = split_options(options[:params])
+
           case from = options[:from]
           when Symbol
-            instantiate_record(get(from, options[:params]))
+            instantiate_record(get(from, query_options), prefix_options)
           when String
-            path = "#{from}#{query_string(options[:params])}"
-            instantiate_record(format.decode(connection.get(path, headers).body))
+            path = "#{from}#{query_string(query_options)}"
+            instantiate_record(format.decode(connection.get(path, headers).body), prefix_options)
           end
         end
 

lib/active_resource/singleton.rb

@@ -96,18 +96,11 @@ def singleton_path(prefix_options = {}, query_options = nil)
       #   Inventory.find
       #   # => raises ResourceNotFound
       def find(options = {})
-        find_singleton(options)
-      end
-
-      private
-        # Find singleton resource
-        def find_singleton(options)
-          prefix_options, query_options = split_options(options[:params])
+        prefix_options, query_options = split_options(options[:params])
+        path = singleton_path(prefix_options, query_options)
 
-          path = singleton_path(prefix_options, query_options)
-          resp = self.format.decode(self.connection.get(path, self.headers).body)
-          instantiate_record(resp, prefix_options)
-        end
+        super(:one, options.merge(from: path, params: prefix_options))
+      end
     end
     # Deletes the resource from the remote service.
     #

test/singleton_test.rb

@@ -69,14 +69,6 @@ def test_singleton_path_with_parameters
     assert_equal "/products/5/inventory.json?sold=true", path
   end
 
-  def test_find_singleton
-    setup_weather
-    weather = Weather.send(:find_singleton, Hash.new)
-    assert_not_nil weather
-    assert_equal "Sunny", weather.status
-    assert_equal 67, weather.temperature
-  end
-
   def test_find
     setup_weather
     weather = Weather.find