Add YamlFrontMatterFilter to the PreProcessPipeline

This filter will detect YAML Front Matter and convert it to an HTML
table for prettier formatting.

1 files changed, 53 insertions, 0 deletions

diff --git a/spec/lib/banzai/filter/yaml_front_matter_filter_spec.rb b/spec/lib/banzai/filter/yaml_front_matter_filter_spec.rb
new file mode 100644
index 00000000000..fe70eada7eb
--- /dev/null
+++ b/spec/lib/banzai/filter/yaml_front_matter_filter_spec.rb
@@ -0,0 +1,53 @@
+require 'rails_helper'
+
+describe Banzai::Filter::YamlFrontMatterFilter, lib: true do
+  include FilterSpecHelper
+
+  it 'allows for `encoding:` before the frontmatter' do
+    content = <<-MD.strip_heredoc
+      # encoding: UTF-8
+      ---
+      foo: foo
+      ---
+
+      # Header
+
+      Content
+    MD
+
+    output = filter(content)
+
+    expect(output).not_to match 'encoding'
+  end
+
+  it 'converts YAML frontmatter to a fenced code block' do
+    content = <<-MD.strip_heredoc
+      ---
+      bar: :bar_symbol
+      ---
+
+      # Header
+
+      Content
+    MD
+
+    output = filter(content)
+
+    aggregate_failures do
+      expect(output).not_to include '---'
+      expect(output).to include "```yaml\nbar: :bar_symbol\n```"
+    end
+  end
+
+  context 'on content without frontmatter' do
+    it 'returns the content unmodified' do
+      content = <<-MD.strip_heredoc
+        # This is some Markdown
+
+        It has no YAML frontmatter to parse.
+      MD
+
+      expect(filter(content)).to eq content
+    end
+  end
+end