Enable hook to be always run with the jekyll serve command

Read the proofer options form _config.checks.yml
Ignore URLs excluded in the Jekyll config

Author: dshevtsov

_checks/html-check-config.yml

@@ -0,0 +1,30 @@
+# The hook runs html-proofer with options defined in the
+#  _checks/html-check-config.yml file
+#
+# For more details about html-proofer, refer to: https://github.com/gjtorikian/html-proofer
+# For more details about Jekyll hooks, refer to: https://jekyllrb.com/docs/plugins/hooks/
+#
+require 'html-proofer'
+require 'yaml'
+
+Jekyll::Hooks.register :site, :post_write do |site|
+
+  # If 'jekyll serve' has been run, read options for html-proofer
+  # in '_config.checks.yml' and merge the 'url_ignore' list with 'excludes'
+  # from Jekyll configurtiuon
+  #
+  if site.config['serving'] == true
+    begin
+      checks_config = YAML.load_file('_config.checks.yml')
+      jekyll_excludes = site.config['exclude']
+      jekyll_excludes_as_regex = jekyll_excludes.map { |item| /#{item}/ }
+      checks_config['html-proofer'][:url_ignore].push(jekyll_excludes_as_regex).flatten!.uniq!
+      options = checks_config['html-proofer']
+      # Run html-proofer to check the jekyll destination directory
+      HTMLProofer.check_directory(site.dest, options).run
+    rescue
+      puts
+      puts 'Fix the broken links before you commit the changes.'.blue
+    end
+  end
+end