Allow Haml >= 5.2 and < 7.

Author: gkellogg

lib/rdf/vocab/extensions.rb

@@ -391,7 +391,12 @@ def to_html(graph: nil, prefixes: nil, jsonld: nil, template: nil)
         case template
         when /.haml$/
           require 'haml'
-          haml = Haml::Engine.new(File.read(template))
+          haml = if Haml.const_defined?(:Template)
+            Haml::Template.new {File.read(template)}
+          else
+           Haml::Engine.new(File.read(template))
+          end
+          
           haml.render(self, ont: expanded, context: json['@context'], prefixes: prefixes)
         when /.erb$/
           require 'erubis'

rdf-vocab.gemspec

@@ -30,7 +30,7 @@ Gem::Specification.new do |gem|
   gem.add_runtime_dependency     'rdf',              '~> 3.2', '>= 3.2.4'
 
   # Either of these are required for HTML vocabulary generation
-  gem.add_development_dependency 'haml',             '~> 5.2'
+  gem.add_development_dependency 'haml',             '>= 5.2', "< 7"
   gem.add_development_dependency 'erubis',           '~> 2.7'
 
   gem.add_development_dependency 'json-ld',          '~> 3.2'