1 files changed, 118 insertions, 0 deletions
diff --git a/spec/lib/banzai/pipeline/plain_markdown_pipeline_spec.rb b/spec/lib/banzai/pipeline/plain_markdown_pipeline_spec.rb
new file mode 100644
index 00000000000..241d6db4f11
--- /dev/null
+++ b/spec/lib/banzai/pipeline/plain_markdown_pipeline_spec.rb
@@ -0,0 +1,118 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Banzai::Pipeline::PlainMarkdownPipeline do
+  using RSpec::Parameterized::TableSyntax
+
+  describe 'backslash escapes' do
+    let_it_be(:project) { create(:project, :public) }
+    let_it_be(:issue)   { create(:issue, project: project) }
+
+    def correct_html_included(markdown, expected)
+      result = described_class.call(markdown, {})
+
+      expect(result[:output].to_html).to include(expected)
+
+      result
+    end
+
+    context 'when feature flag honor_escaped_markdown is disabled' do
+      before do
+        stub_feature_flags(honor_escaped_markdown: false)
+      end
+
+      it 'does not escape the markdown' do
+        result = described_class.call(%q(\!), project: project)
+        output = result[:output].to_html
+
+        expect(output).to eq('<p data-sourcepos="1:1-1:2">!</p>')
+        expect(result[:escaped_literals]).to be_falsey
+      end
+    end
+
+    # Test strings taken from https://spec.commonmark.org/0.29/#backslash-escapes
+    describe 'CommonMark tests', :aggregate_failures do
+      it 'converts all ASCII punctuation to literals' do
+        markdown = %q(\!\"\#\$\%\&\'\*\+\,\-\.\/\:\;\<\=\>\?\@\[\]\^\_\`\{\|\}\~) + %q[\(\)\\\\]
+        punctuation = %w(! " # $ % &amp; ' * + , - . / : ; &lt; = &gt; ? @ [ \\ ] ^ _ ` { | } ~) + %w[( )]
+
+        result = described_class.call(markdown, project: project)
+        output = result[:output].to_html
+
+        punctuation.each { |char| expect(output).to include("<span>#{char}</span>") }
+        expect(result[:escaped_literals]).to be_truthy
+      end
+
+      it 'does not convert other characters to literals' do
+        markdown = %q(\→\A\a\ \3\φ\«)
+        expected = '\→\A\a\ \3\φ\«'
+
+        result = correct_html_included(markdown, expected)
+        expect(result[:escaped_literals]).to be_falsey
+      end
+
+      describe 'escaped characters are treated as regular characters and do not have their usual Markdown meanings' do
+        where(:markdown, :expected) do
+          %q(\*not emphasized*)              | %q(<span>*</span>not emphasized*)
+          %q(\<br/> not a tag)               | %q(<span>&lt;</span>br/&gt; not a tag)
+          %q!\[not a link](/foo)!            | %q!<span>[</span>not a link](/foo)!
+          %q(\`not code`)                    | %q(<span>`</span>not code`)
+          %q(1\. not a list)                 | %q(1<span>.</span> not a list)
+          %q(\# not a heading)               | %q(<span>#</span> not a heading)
+          %q(\[foo]: /url "not a reference") | %q(<span>[</span>foo]: /url "not a reference")
+          %q(\&ouml; not a character entity) | %q(<span>&amp;</span>ouml; not a character entity)
+        end
+
+        with_them do
+          it 'keeps them as literals' do
+            correct_html_included(markdown, expected)
+          end
+        end
+      end
+
+      it 'backslash is itself escaped, the following character is not' do
+        markdown = %q(\\\\*emphasis*)
+        expected = %q(<span>\</span><em>emphasis</em>)
+
+        correct_html_included(markdown, expected)
+      end
+
+      it 'backslash at the end of the line is a hard line break' do
+        markdown = <<~MARKDOWN
+          foo\\
+          bar
+        MARKDOWN
+        expected = "foo<br>\nbar"
+
+        correct_html_included(markdown, expected)
+      end
+
+      describe 'backslash escapes do not work in code blocks, code spans, autolinks, or raw HTML' do
+        where(:markdown, :expected) do
+          %q(`` \[\` ``)       | %q(<code>\[\`</code>)
+          %q(    \[\])         | %Q(<code>\\[\\]\n</code>)
+          %Q(~~~\n\\[\\]\n~~~) | %Q(<code>\\[\\]\n</code>)
+          %q(<http://example.com?find=\*>) | %q(<a href="http://example.com?find=%5C*">http://example.com?find=\*</a>)
+          %q[<a href="/bar\/)">]           | %q[<a href="/bar%5C/)">]
+        end
+
+        with_them do
+          it { correct_html_included(markdown, expected) }
+        end
+      end
+
+      describe 'work in all other contexts, including URLs and link titles, link references, and info strings in fenced code blocks' do
+        where(:markdown, :expected) do
+          %q![foo](/bar\* "ti\*tle")!            | %q(<a href="/bar*" title="ti*tle">foo</a>)
+          %Q![foo]\n\n[foo]: /bar\\* "ti\\*tle"! | %q(<a href="/bar*" title="ti*tle">foo</a>)
+          %Q(``` foo\\+bar\nfoo\n```)            | %Q(<code lang="foo+bar">foo\n</code>)
+        end
+
+        with_them do
+          it { correct_html_included(markdown, expected) }
+        end
+      end
+    end
+  end
+end