Use to_a to pre-buffer the collection

We can safely assume we're not dealing with an infinite collection as
we're about to call `each` on it and collect the results until it
terminates on its own. Given that, `to_a` is implemented by the normal
Array-like objects, and less Array-like objects like `Enumerator` and
`Enumerator::Lazy`.

actionview/CHANGELOG.md

@@ -1,11 +1,11 @@
 *   Changed partial rendering with a collection to allow collections which
-    don't implement `to_ary`.
+    implement `to_a`.
 
-    Extracting the collection option has an optimization to avoid unnecessary
-    queries of ActiveRecord Relations by calling `to_ary` on the given
+    Extracting the collection option had an optimization to avoid unnecessary
+    queries of ActiveRecord Relations by calling `#to_ary` on the given
     collection. Instances of `Enumerator` or `Enumerable` are valid
-    collections, but they do not implement `#to_ary`. They will now be
-    extracted and rendered as expected.
+    collections, but they do not implement `#to_ary`. By changing this to
+    `#to_a`, they will now be extracted and rendered as expected.
 
     *Steven Harman*
 

actionview/lib/action_view/renderer/partial_renderer.rb

@@ -403,9 +403,8 @@ def setup(context, options, block)
 
     def collection_from_options
       if @options.key?(:collection)
-        collection = @options[:collection] || []
-        collection = collection.to_ary if collection.respond_to?(:to_ary)
-        collection
+        collection = @options[:collection]
+        collection ? collection.to_a : []
       end
     end