(#302) Fix warnings generated by ERB.new

This has to special case Ruby <2.6.0 since those versions will interpret
the keyword argument as a hash passed as the second argument.

Without this change running this code in Ruby 2.6+ will generate
warnings about the parameters passed to `ERB.new`.

Author: danielparks

Diff for: lib/puppet-strings/markdown/base.rb

@@ -172,9 +172,9 @@ def word_wrap(text, line_width: 120, break_sequence: "\n")
 
     # @return [String] full markdown rendering of a component
     def render(template)
+      file = File.join(File.dirname(__FILE__), 'templates', template)
       begin
-        file = File.join(File.dirname(__FILE__),"templates/#{template}")
-        ERB.new(File.read(file), nil, '-').result(binding)
+        PuppetStrings::Markdown.erb(file).result(binding)
       rescue StandardError => e
         fail "Processing #{@registry[:file]}:#{@registry[:line]} with #{file} => #{e}"
       end
@@ -199,4 +199,17 @@ def clean_link(input)
       input.tr('^a-zA-Z0-9_-', '-')
     end
   end
+
+  # Helper function to load an ERB template.
+  #
+  # @param [String] path The full path to the template file.
+  # @return [ERB] Template
+  def self.erb(path)
+    if Gem::Version.new(RUBY_VERSION) >= Gem::Version.new('2.6.0')
+      ERB.new(File.read(path), trim_mode: '-')
+    else
+      # This outputs warnings in Ruby 2.6+.
+      ERB.new(File.read(path), nil, '-')
+    end
+  end
 end

Diff for: lib/puppet-strings/markdown/table_of_contents.rb

@@ -17,8 +17,8 @@ def self.render
         group = toc
         priv = r.contains_private?
 
-        template = File.join(File.dirname(__FILE__),"templates/table_of_contents.erb")
-        final += ERB.new(File.read(template), nil, '-').result(binding)
+        template = File.join(File.dirname(__FILE__), 'templates/table_of_contents.erb')
+        final += PuppetStrings::Markdown.erb(template).result(binding)
       end
       final
     end