Improve encoding detection for link cards (#30780)

2025-02-06 15:05:07 +00:00 · 2024-06-21 14:51:10 +02:00 · 2024-06-21 14:51:10 +02:00 · 2cab1c7b09
commit 2cab1c7b09
parent 4e6db5e284
3 changed files with 36 additions and 5 deletions
--- a/app/lib/link_details_extractor.rb
+++ b/app/lib/link_details_extractor.rb
@ -269,15 +269,20 @@ class LinkDetailsExtractor
  end

  def document
-    @document ||= Nokogiri::HTML(@html, nil, encoding)
+    @document ||= detect_encoding_and_parse_document
  end

-  def encoding
-    @encoding ||= begin
+  def detect_encoding_and_parse_document
+    [detect_encoding, nil, @html_charset, 'UTF-8'].uniq.each do |encoding|
+      document = Nokogiri::HTML(@html, nil, encoding)
+      return document if document.to_s.valid_encoding?
+    end
+  end
+
+  def detect_encoding
    guess = detector.detect(@html, @html_charset)
    guess&.fetch(:confidence, 0).to_i > 60 ? guess&.fetch(:encoding, nil) : nil
  end
-  end

  def detector
    @detector ||= CharlockHolmes::EncodingDetector.new.tap do |detector|
--- a/spec/fixtures/requests/low_confidence_latin1.txt
+++ b/spec/fixtures/requests/low_confidence_latin1.txt
@ -0,0 +1,17 @@
+HTTP/1.1 200 OK
+server: nginx
+date: Thu, 13 Jun 2024 14:33:13 GMT
+content-type: text/html; charset=ISO-8859-1
+content-length: 158
+accept-ranges: bytes
+
+<!doctype html>
+<html lang="en">
+<head>
+  <meta charset="UTF-8">
+  <title>Tofu á l'orange</title>
+</head>
+<body>
+  <h2>Tofu á l'orange</h2>
+</body>
+</html>
--- a/spec/services/fetch_link_card_service_spec.rb
+++ b/spec/services/fetch_link_card_service_spec.rb
@ -26,6 +26,7 @@ RSpec.describe FetchLinkCardService do
    stub_request(:get, 'http://example.com/sjis_with_wrong_charset').to_return(request_fixture('sjis_with_wrong_charset.txt'))
    stub_request(:get, 'http://example.com/koi8-r').to_return(request_fixture('koi8-r.txt'))
    stub_request(:get, 'http://example.com/windows-1251').to_return(request_fixture('windows-1251.txt'))
+    stub_request(:get, 'http://example.com/low_confidence_latin1').to_return(request_fixture('low_confidence_latin1.txt'))

    Rails.cache.write('oembed_endpoint:example.com', oembed_cache) if oembed_cache

@ -148,6 +149,14 @@ RSpec.describe FetchLinkCardService do
      end
    end

+    context 'with a URL of a page in ISO-8859-1 encoding, that charlock_holmes cannot detect' do
+      let(:status) { Fabricate(:status, text: 'Check out http://example.com/low_confidence_latin1') }
+
+      it 'decodes the HTML' do
+        expect(status.preview_card.title).to eq("Tofu á l'orange")
+      end
+    end
+
    context 'with a Japanese path URL' do
      let(:status) { Fabricate(:status, text: 'テストhttp://example.com/日本語') }