Validate the presence of required attributes.

circleco · Sep 9, 2017 · 71dea58 · 71dea58
1 parent 023ce7d
commit 71dea58
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Showing 3 changed files with 37 additions and 1 deletion.
diff --git a/lib/ogp/open_graph.rb b/lib/ogp/open_graph.rb
@@ -3,16 +3,28 @@
 REQUIRED_ATTRIBUTES = %w(title type image url)
 
 module OGP
+  class MissingAttributeError < StandardError
+  end
+
   class OpenGraph
     attr_accessor :title, :type, :image, :url
 
     def initialize(source)
       document = Oga.parse_html(source)
+      check_required_attributes(document)
       parse_required_attributes(document)
     end
 
     private
 
+    def check_required_attributes(document)
+      REQUIRED_ATTRIBUTES.each do |attribute_name|
+        if !attribute_exists(document, attribute_name)
+          raise MissingAttributeError.new("Missing required attribute: #{attribute_name}")
+        end
+      end
+    end
+
     def parse_required_attributes(document)
       REQUIRED_ATTRIBUTES.each do |attribute_name|
         instance_variable_set("@#{attribute_name}", parse_attribute(document, attribute_name))
@@ -22,5 +34,9 @@ def parse_required_attributes(document)
     def parse_attribute(document, name)
       document.at_xpath("//head/meta[@property='og:#{name}']").get('content')
     end
+
+    def attribute_exists(document, name)
+      document.at_xpath("boolean(//head/meta[@property='og:#{name}'])")
+    end
   end
 end
diff --git a/spec/lib/open_graph_spec.rb b/spec/lib/open_graph_spec.rb
@@ -3,14 +3,23 @@
 describe OGP::OpenGraph do
   describe '#initialize' do
     context 'with strictly the required attributes' do
-      it 'should parse attributes properly' do
+      it 'should create a proper OpenGraph object' do
         content = File.read("#{File.dirname(__FILE__)}/../view/required_attributes.html")
         open_graph = OGP::OpenGraph.new(content)
+
         expect(open_graph.title).to eql('The Rock')
         expect(open_graph.type).to eql('video.movie')
         expect(open_graph.url).to eql('http://www.imdb.com/title/tt0117500/')
         expect(open_graph.image).to eql('http://ia.media-imdb.com/images/rock.jpg')
       end
     end
+
+    context 'with missing one of the required attributes' do
+      it 'should raise an error' do
+        content = File.read("#{File.dirname(__FILE__)}/../view/missing_required_attributes.html")
+
+        expect{OGP::OpenGraph.new(content)}.to raise_error(OGP::MissingAttributeError)
+      end
+    end
   end
 end
diff --git a/spec/view/missing_required_attributes.html b/spec/view/missing_required_attributes.html
@@ -0,0 +1,11 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <meta content="The Rock" property="og:title">
+  <meta content="video.movie" property="og:type">
+  <meta content="http://www.imdb.com/title/tt0117500/" property="og:url">
+  <title></title>
+</head>
+<body>
+</body>
+</html>