diff --git a/lib/banzai/filter/yaml_front_matter_filter.rb b/lib/banzai/filter/yaml_front_matter_filter.rb new file mode 100644 index 00000000000..e4e2f3f228d --- /dev/null +++ b/lib/banzai/filter/yaml_front_matter_filter.rb @@ -0,0 +1,28 @@ +require 'html/pipeline/filter' +require 'yaml' + +module Banzai + module Filter + class YamlFrontMatterFilter < HTML::Pipeline::Filter + DELIM = '---'.freeze + + # Hat-tip to Middleman: https://git.io/v2e0z + PATTERN = %r{ + \A(?:[^\r\n]*coding:[^\r\n]*\r?\n)? + (?#{DELIM})[ ]*\r?\n + (?.*?)[ ]*\r?\n? + ^(?#{DELIM})[ ]*\r?\n? + \r?\n? + (?.*) + }mx.freeze + + def call + match = PATTERN.match(html) + + return html unless match + + "```yaml\n#{match['frontmatter']}\n```\n\n#{match['content']}" + end + end + end +end diff --git a/lib/banzai/pipeline/pre_process_pipeline.rb b/lib/banzai/pipeline/pre_process_pipeline.rb index c174f0b862d..50dc978b452 100644 --- a/lib/banzai/pipeline/pre_process_pipeline.rb +++ b/lib/banzai/pipeline/pre_process_pipeline.rb @@ -2,7 +2,8 @@ module Banzai module Pipeline class PreProcessPipeline < BasePipeline def self.filters - [ + FilterArray[ + Filter::YamlFrontMatterFilter ] end 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