Ignore low-confidence CharlockHolmes guesses when parsing link cards (#9510)

* Add failing test for windows-1251 link cards * Ignore low-confidence CharlockHolmes guesses Fixes #9466 * Fix no method error when charlock holmes cannot detect charset

Ignore low-confidence CharlockHolmes guesses when parsing link cards (#9510)
e709b8da · ThibG · Eugen Rochko · 4ede5174 · e709b8da · e709b8da
--- a/app/services/fetch_link_card_service.rb
+++ b/app/services/fetch_link_card_service.rb
@@ -137,7 +137,8 @@ class FetchLinkCardService < BaseService
    detector.strip_tags = true

    guess      = detector.detect(@html, @html_charset)
-    page       = Nokogiri::HTML(@html, nil, guess&.fetch(:encoding, nil))
+    encoding   = guess&.fetch(:confidence, 0).to_i > 60 ? guess&.fetch(:encoding, nil) : nil
+    page       = Nokogiri::HTML(@html, nil, encoding)
    player_url = meta_property(page, 'twitter:player')

    if player_url && !bad_url?(Addressable::URI.parse(player_url))

--- a/spec/fixtures/requests/windows-1251.txt
+++ b/spec/fixtures/requests/windows-1251.txt
+HTTP/1.1 200 OK
+server: nginx
+date: Wed, 12 Dec 2018 13:14:03 GMT
+content-type: text/html
+content-length: 190
+accept-ranges: bytes
+
+<!DOCTYPE html>
+<html>
+<head>
+  <meta http-equiv="Content-Type" content="text/html; charset=windows-1251" />
+  <title> </title>
+</head>
+<body>
+  <p> </p>
+</body>
+</html>
--- a/spec/services/fetch_link_card_service_spec.rb
+++ b/spec/services/fetch_link_card_service_spec.rb
@@ -17,6 +17,8 @@ RSpec.describe FetchLinkCardService, type: :service do
    stub_request(:head, 'https://github.com/qbi/WannaCry').to_return(status: 404)
    stub_request(:head, 'http://example.com/test-').to_return(status: 200, headers: { 'Content-Type' => 'text/html' })
    stub_request(:get, 'http://example.com/test-').to_return(request_fixture('idn.txt'))
+    stub_request(:head, 'http://example.com/windows-1251').to_return(status: 200, headers: { 'Content-Type' => 'text/html' })
+    stub_request(:get, 'http://example.com/windows-1251').to_return(request_fixture('windows-1251.txt'))

    subject.call(status)
  end
@@ -57,6 +59,15 @@ RSpec.describe FetchLinkCardService, type: :service do
      end
    end

+    context do
+      let(:status) { Fabricate(:status, text: 'Check out http://example.com/windows-1251') }
+
+      it 'works with windows-1251' do
+        expect(a_request(:get, 'http://example.com/windows-1251')).to have_been_made.at_least_once
+        expect(status.preview_cards.first.title).to eq('сэмпл текст')
+      end
+    end
+
    context do
      let(:status) { Fabricate(:status, text: 'テストhttp://example.com/日本語') }