Introduce a context for rendering fixtures ERB.

Fixture files are passed through an ERB renderer before being read as
YAML. The rendering is currently done in the context of the main object,
so method definitons leak into other fixtures, and there is no clean
place to define fixture helpers.

After this commit, the ERB renderer will use a new subclass of
ActiveRecord::FixtureSet.context_class each time a fixture is rendered.

1 files changed, 55 insertions, 0 deletions

diff --git a/activerecord/test/cases/fixture_set/file_test.rb b/activerecord/test/cases/fixture_set/file_test.rb
index a029fedbd3..92efa8aca7 100644
--- a/activerecord/test/cases/fixture_set/file_test.rb
+++ b/activerecord/test/cases/fixture_set/file_test.rb
@@ -68,6 +68,61 @@ module ActiveRecord
         end
       end
 
+      def test_render_context_helper
+        ActiveRecord::FixtureSet.context_class.class_eval do
+          def fixture_helper
+            "Fixture helper"
+          end
+        end
+        yaml = "one:\n  name: <%= fixture_helper %>\n"
+        tmp_yaml ['curious', 'yml'], yaml do |t|
+          golden =
+              [["one", {"name" => "Fixture helper"}]]
+          assert_equal golden, File.open(t.path) { |fh| fh.to_a }
+        end
+        ActiveRecord::FixtureSet.context_class.class_eval do
+          remove_method :fixture_helper
+        end
+      end
+
+      def test_render_context_lookup_scope
+        yaml = <<END
+one:
+  ActiveRecord: <%= defined? ActiveRecord %>
+  ActiveRecord_FixtureSet: <%= defined? ActiveRecord::FixtureSet %>
+  FixtureSet: <%= defined? FixtureSet %>
+  ActiveRecord_FixtureSet_File: <%= defined? ActiveRecord::FixtureSet::File %>
+  File: <%= File.name %>
+END
+
+        golden = [['one', {
+          'ActiveRecord' => 'constant',
+          'ActiveRecord_FixtureSet' => 'constant',
+          'FixtureSet' => nil,
+          'ActiveRecord_FixtureSet_File' => 'constant',
+          'File' => 'File'
+        }]]
+
+        tmp_yaml ['curious', 'yml'], yaml do |t|
+          assert_equal golden, File.open(t.path) { |fh| fh.to_a }
+        end
+      end
+
+      # Make sure that each fixture gets its own rendering context so that
+      # fixtures are independent.
+      def test_independent_render_contexts
+        yaml1 = "<% def leaked_method; 'leak'; end %>\n"
+        yaml2 = "one:\n  name: <%= leaked_method %>\n"
+        tmp_yaml ['leaky', 'yml'], yaml1 do |t1|
+          tmp_yaml ['curious', 'yml'], yaml2 do |t2|
+            File.open(t1.path) { |fh| fh.to_a }
+            assert_raises(NameError) do
+              File.open(t2.path) { |fh| fh.to_a }
+            end
+          end
+        end
+      end
+
       private
       def tmp_yaml(name, contents)
         t = Tempfile.new name