Bail from frontmatterpropertyexists check if not properties configured

Also adds the ability to accept messages from successful checks

Author: mpchadwick

lib/jekyll-pre-commit/checks/front_matter_property_exists.rb

@@ -3,6 +3,11 @@ module PreCommit
     module Check
       class FrontMatterPropertyExists < Check
         def Check(staged, not_staged, site, args)
+          if !args["properties"]
+            @result[:message] += "No properties to check."
+            return @result
+          end
+
           staged.each do |post|
             args["properties"].each do |property|
               if !post.data[property]

lib/jekyll-pre-commit/runner.rb

@@ -32,6 +32,8 @@ def run(site, staged_files)
           r = o.Check(staged_posts, not_staged_posts, site, c)
           if !r[:ok]
             result[:ok] = false
+          end
+          if r[:message] != ""
             result[:messages].push(r[:message])
           end
         end

spec/jekyll-pre-commit_spec.rb

@@ -50,6 +50,17 @@
     end
   end
 
+  context "with FrontMatterPropertyExistsCheck not checking any properties" do
+    pre_commit_config = {"check" => "FrontMatterPropertyExists"}
+    let(:site) { build_site({ 'pre-commit' => [pre_commit_config] }) }
+
+    it "succeeds with no properties to check message" do
+      result = runner.run(site, ["spec/fixtures/_posts/2017-01-06-no-description.md"])
+      expect(result[:ok]).to eql(true)
+      expect(result[:messages]).to match_array(["No properties to check."])
+    end
+  end
+
   context "with description is not duplicate check" do
     let(:site) { build_site({'pre-commit' => [{"check" => "DescriptionIsNotDuplicate"}]}) }