Gracefully handle errors in syntax highlighting by leaving the block unformatted

Closes #2433

1 files changed, 22 insertions, 0 deletions

diff --git a/spec/lib/gitlab/markdown/syntax_highlight_filter_spec.rb b/spec/lib/gitlab/markdown/syntax_highlight_filter_spec.rb
new file mode 100644
index 00000000000..ecef31853f4
--- /dev/null
+++ b/spec/lib/gitlab/markdown/syntax_highlight_filter_spec.rb
@@ -0,0 +1,22 @@
+require 'spec_helper'
+
+module Gitlab::Markdown
+  describe SyntaxHighlightFilter do
+    include FilterSpecHelper
+
+    let(:project)   { create(:empty_project) }
+    let(:reference) { snippet.to_reference }
+
+    it 'highlights valid code blocks' do
+      result = filter('<pre><code>def fun end</code>')
+      expect(result.to_html).to eq("<pre class=\"code highlight js-syntax-highlight plaintext\"><code>def fun end</code></pre>\n")
+    end
+
+    it 'passes through invalid code blocks' do
+      allow_any_instance_of(SyntaxHighlightFilter).to receive(:block_code).and_raise(StandardError)
+
+      result = filter('<pre><code>This is a test</code></pre>')
+      expect(result.to_html).to eq('<pre>This is a test</pre>')
+    end
+  end
+end