Fix structured data parsing from links choking on bad data (mastodon#…

…17403) * Fix structured data parsing from links choking on bad data - Fix og:url meta tag being prioritized over canonical link tag - Fix structured data parsing choking on commented-out CDATA declarations - Fix HTML entities in title, description, provider_name, author_name - Change structured data parsing to attempt every JSON-LD script tag * Remove unnecessary slash escapes from CDATA regex pattern
hachyderm · Feb 7, 2022 · f1f6ddd · f1f6ddd
1 parent 73a7823
commit f1f6ddd
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Showing 2 changed files with 166 additions and 9 deletions.
diff --git a/app/lib/link_details_extractor.rb b/app/lib/link_details_extractor.rb
@@ -3,6 +3,19 @@
 class LinkDetailsExtractor
   include ActionView::Helpers::TagHelper
 
+  # Some publications wrap their JSON-LD data in their <script> tags
+  # in commented-out CDATA blocks, they need to be removed before
+  # attempting to parse JSON
+  CDATA_JUNK_PATTERN = %r{^[\s]*(
+    (/\*[\s]*<!\[CDATA\[[\s]*\*/) # Block comment style opening
+    |
+    (//[\s]*<!\[CDATA\[) # Single-line comment style opening
+    |
+    (/\*[\s]*\]\]>[\s]*\*/) # Block comment style closing
+    |
+    (//[\s]*\]\]>) # Single-line comment style closing
+  )[\s]*$}x
+
   class StructuredData
     SUPPORTED_TYPES = %w(
       NewsArticle
@@ -61,6 +74,10 @@ def publisher_logo
       publisher.dig('logo', 'url')
     end
 
+    def valid?
+      json.present?
+    end
+
     private
 
     def author
@@ -134,31 +151,31 @@ def height
   end
 
   def title
-    structured_data&.headline || opengraph_tag('og:title') || document.xpath('//title').map(&:content).first
+    html_entities.decode(structured_data&.headline || opengraph_tag('og:title') || document.xpath('//title').map(&:content).first)
   end
 
   def description
-    structured_data&.description || opengraph_tag('og:description') || meta_tag('description')
+    html_entities.decode(structured_data&.description || opengraph_tag('og:description') || meta_tag('description'))
   end
 
   def image
     valid_url_or_nil(opengraph_tag('og:image'))
   end
 
   def canonical_url
-    valid_url_or_nil(opengraph_tag('og:url') || link_tag('canonical'), same_origin_only: true) || @original_url.to_s
+    valid_url_or_nil(link_tag('canonical') || opengraph_tag('og:url'), same_origin_only: true) || @original_url.to_s
   end
 
   def provider_name
-    structured_data&.publisher_name || opengraph_tag('og:site_name')
+    html_entities.decode(structured_data&.publisher_name || opengraph_tag('og:site_name'))
   end
 
   def provider_url
     valid_url_or_nil(host_to_url(opengraph_tag('og:site')))
   end
 
   def author_name
-    structured_data&.author_name || opengraph_tag('og:author') || opengraph_tag('og:author:username')
+    html_entities.decode(structured_data&.author_name || opengraph_tag('og:author') || opengraph_tag('og:author:username'))
   end
 
   def author_url
@@ -223,10 +240,24 @@ def meta_tag(name)
 
   def structured_data
     @structured_data ||= begin
-      json_ld = document.xpath('//script[@type="application/ld+json"]').map(&:content).first
-      json_ld.present? ? StructuredData.new(json_ld) : nil
-    rescue Oj::ParseError
-      nil
+      # Some publications have more than one JSON-LD definition on the page,
+      # and some of those definitions aren't valid JSON either, so we have
+      # to loop through here until we find something that is the right type
+      # and doesn't break
+      document.xpath('//script[@type="application/ld+json"]').filter_map do |element|
+        json_ld = element.content&.gsub(CDATA_JUNK_PATTERN, '')
+
+        next if json_ld.blank?
+
+        structured_data = StructuredData.new(html_entities.decode(json_ld))
+
+        next unless structured_data.valid?
+
+        structured_data
+      rescue Oj::ParseError, EncodingError
+        Rails.logger.debug("Invalid JSON-LD in #{@original_url}")
+        next
+      end.first
     end
   end
 
@@ -246,4 +277,8 @@ def detector
       detector.strip_tags = true
     end
   end
+
+  def html_entities
+    @html_entities ||= HTMLEntities.new
+  end
 end
diff --git a/spec/lib/link_details_extractor_spec.rb b/spec/lib/link_details_extractor_spec.rb
@@ -26,4 +26,126 @@
       end
     end
   end
+
+  context 'when structured data is present' do
+    let(:original_url) { 'https://example.com/page.html' }
+
+    context 'and is wrapped in CDATA tags' do
+      let(:html) { <<-HTML }
+<!doctype html>
+<html>
+<head>
+  <script type="application/ld+json">
+  //<![CDATA[
+  {"@context":"http://schema.org","@type":"NewsArticle","mainEntityOfPage":"https://example.com/page.html","headline":"Foo","datePublished":"2022-01-31T19:53:00+00:00","url":"https://example.com/page.html","description":"Bar","author":{"@type":"Person","name":"Hoge"},"publisher":{"@type":"Organization","name":"Baz"}}
+  //]]>
+  </script>
+</head>
+</html>
+      HTML
+
+      describe '#title' do
+        it 'returns the title from structured data' do
+          expect(subject.title).to eq 'Foo'
+        end
+      end
+
+      describe '#description' do
+        it 'returns the description from structured data' do
+          expect(subject.description).to eq 'Bar'
+        end
+      end
+
+      describe '#provider_name' do
+        it 'returns the provider name from structured data' do
+          expect(subject.provider_name).to eq 'Baz'
+        end
+      end
+
+      describe '#author_name' do
+        it 'returns the author name from structured data' do
+          expect(subject.author_name).to eq 'Hoge'
+        end
+      end
+    end
+
+    context 'but the first tag is invalid JSON' do
+      let(:html) { <<-HTML }
+<!doctype html>
+<html>
+<body>
+  <script type="application/ld+json">
+    {
+      "@context":"https://schema.org",
+      "@type":"ItemList",
+      "url":"https://example.com/page.html",
+      "name":"Foo",
+      "description":"Bar"
+    },
+    {
+      "@context": "https://schema.org",
+      "@type": "BreadcrumbList",
+      "itemListElement":[
+        {
+          "@type":"ListItem",
+          "position":1,
+          "item":{
+            "@id":"https://www.example.com",
+            "name":"Baz"
+          }
+        }
+      ]
+    }
+  </script>
+  <script type="application/ld+json">
+    {
+      "@context":"https://schema.org",
+      "@type":"NewsArticle",
+      "mainEntityOfPage": {
+        "@type":"WebPage",
+        "@id": "http://example.com/page.html"
+      },
+      "headline": "Foo",
+      "description": "Bar",
+      "datePublished": "2022-01-31T19:46:00+00:00",
+      "author": {
+        "@type": "Organization",
+        "name": "Hoge"
+      },
+      "publisher": {
+        "@type": "NewsMediaOrganization",
+        "name":"Baz",
+        "url":"https://example.com/"
+      }
+    }
+  </script>
+</body>
+</html>
+      HTML
+
+      describe '#title' do
+        it 'returns the title from structured data' do
+          expect(subject.title).to eq 'Foo'
+        end
+      end
+
+      describe '#description' do
+        it 'returns the description from structured data' do
+          expect(subject.description).to eq 'Bar'
+        end
+      end
+
+      describe '#provider_name' do
+        it 'returns the provider name from structured data' do
+          expect(subject.provider_name).to eq 'Baz'
+        end
+      end
+
+      describe '#author_name' do
+        it 'returns the author name from structured data' do
+          expect(subject.author_name).to eq 'Hoge'
+        end
+      end
+    end
+  end
 end