Do not add doc separator when render result is blank

CHANGELOG.md

@@ -1,5 +1,8 @@
 ## next
 
+*Bug fixes*
+- Fixes a bug introduced in 0.26.2 where kubernetes-render started adding YAML headers to empty render results
+
 ## 0.26.2
 
 *Enhancements*

lib/kubernetes-deploy/render_task.rb

@@ -70,7 +70,7 @@ def render_filename(filename, stream)
       rendered_content = @renderer.render_template(filename, file_content)
       implicit = true
       YAML.parse_stream(rendered_content, "<rendered> #{filename}") { |d| implicit = d.implicit }
-      stream.puts "---\n" if implicit
+      stream.puts "---\n" if implicit && rendered_content.present?
       stream.puts rendered_content
       @logger.info("Rendered #{File.basename(filename)}")
     rescue Psych::SyntaxError => exception

test/fixtures/collection-with-erb/effectively_empty.yml.erb

@@ -0,0 +1,9 @@
+<%- if false -%>
+---
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: never-created
+data:
+  will_never: exist
+<%- end -%>

test/integration/render_task_test.rb

@@ -308,6 +308,14 @@ def test_render_preserves_duplicate_keys
     end
   end
 
+  def test_render_does_not_generate_extra_blank_documents_when_file_is_empty
+    renderer = build_render_task(fixture_path('collection-with-erb'))
+    assert_render_success(renderer.run(mock_output_stream, ['effectively_empty.yml.erb']))
+    stdout_assertion do |output|
+      assert_equal "", output.strip
+    end
+  end
+
   private
 
   def build_render_task(template_dir, bindings = {})