De-dup Templates, introduce UnboundTemplate

Previously it's possible to have multiple copies of the "same" Template.
For example, if index.html.erb is found both the :en and :fr locale, it
will return a different Template object for each. The same can happen
with formats, variants, and handlers.

This commit de-duplicates templates, there will now only be one template
per file/virtual_path/locals tuple.

We need to consider virtual_path because both `render "index"`, and
`render "index.html"` can both find the same file but will have
different virtual_paths. IMO this is rare and should be
deprecated/removed, but it exists now so we need to consider it in order
to cache correctly.

This commit introduces a new UnboundTemplate class, which represents a
template with unknown locals. Template objects can be built from it by
using `#with_locals`. Currently, this is just a convenience around
caching templates, but I hope it's a helpful concept that could have
more utility in the future.

1 files changed, 30 insertions, 0 deletions

diff --git a/actionview/test/template/resolver_shared_tests.rb b/actionview/test/template/resolver_shared_tests.rb
index dee6a69c66..37bdf4b22c 100644
--- a/actionview/test/template/resolver_shared_tests.rb
+++ b/actionview/test/template/resolver_shared_tests.rb
@@ -13,6 +13,10 @@ module ResolverSharedTests
     File.write(path, source)
   end
 
+  def context
+    @context ||= ActionView::LookupContext.new(resolver)
+  end
+
   def test_can_find_with_no_extensions
     with_file "test/hello_world", "Hello default!"
 
@@ -82,4 +86,30 @@ module ResolverSharedTests
     templates = resolver.find_all("hello_world", "test", false, locale: [], formats: [:xml], variants: :any, handlers: [:erb])
     assert_equal 0, templates.size
   end
+
+  def test_found_template_is_cached
+    with_file "test/hello_world.html.erb", "Hello HTML!"
+
+    a = context.find("hello_world", "test", false, [], {})
+    b = context.find("hello_world", "test", false, [], {})
+    assert_same a, b
+  end
+
+  def test_same_template_from_different_details_is_same_object
+    with_file "test/hello_world.html.erb", "Hello plain text!"
+
+    a = context.find("hello_world", "test", false, [], locale: [:en])
+    b = context.find("hello_world", "test", false, [], locale: [:fr])
+    assert_same a, b
+  end
+
+  def test_virtual_path_is_preserved_with_dot
+    with_file "test/hello_world.html.erb", "Hello html!"
+
+    template = context.find("hello_world.html", "test", false, [], {})
+    assert_equal "test/hello_world.html", template.virtual_path
+
+    template = context.find("hello_world", "test", false, [], {})
+    assert_equal "test/hello_world", template.virtual_path
+  end
 end