A fast, safe, extensible parser for CommonMark. This wraps the comrak Rust crate.


Keywords
commonmark, html, libcmark
License
MIT
Install
gem install commonmarker -v 0.20.1

Documentation

Commonmarker

Note This README refers to the behavior in the new 1.0.0.pre gem.

Ruby wrapper for Rust's comrak crate.

It passes all of the CommonMark test suite, and is therefore spec-complete. It also includes extensions to the CommonMark spec as documented in the GitHub Flavored Markdown spec, such as support for tables, strikethroughs, and autolinking.

For more information on available extensions, see the documentation below.

Installation

Add this line to your application's Gemfile:

gem 'commonmarker'

And then execute:

$ bundle

Or install it yourself as:

$ gem install commonmarker

Usage

Converting to HTML

Call to_html on a string to convert it to HTML:

require 'commonmarker'
Commonmarker.to_html('"Hi *there*"', options: {
    parse: { smart: true }
})
# <p>“Hi <em>there</em>”</p>\n

The second argument is optional--see below for more information.

Options and plugins

Options

Commonmarker accepts the same parse, render, and extensions options that comrak does, as a hash dictionary with symbol keys:

Commonmarker.to_html('"Hi *there*"', options:{
  parse: { smart: true },
  render: { hardbreaks: false}
})

Note that there is a distinction in comrak for "parse" options and "render" options, which are represented in the tables below.

Parse options

Name Description Default
smart Punctuation (quotes, full-stops and hyphens) are converted into 'smart' punctuation. false
default_info_string The default info string for fenced code blocks. ""

Render options

Name Description Default
hardbreaks Soft line breaks translate into hard line breaks. true
github_pre_lang GitHub-style <pre lang="xyz"> is used for fenced code blocks with info tags. true
width The wrap column when outputting CommonMark. 80
unsafe Allow rendering of raw HTML and potentially dangerous links. false
escape Escape raw HTML instead of clobbering it. false
sourcepos Include source position attribute in HTML and XML output. false

As well, there are several extensions which you can toggle in the same manner:

Commonmarker.to_html('"Hi *there*"', options: {
    extension: { footnotes: true, description_lists: true },
    render: { hardbreaks: false}
})

Extension options

Name Description Default
strikethrough Enables the strikethrough extension from the GFM spec. true
tagfilter Enables the tagfilter extension from the GFM spec. true
table Enables the table extension from the GFM spec. true
autolink Enables the autolink extension from the GFM spec. true
tasklist Enables the task list extension from the GFM spec. true
superscript Enables the superscript Comrak extension. false
header_ids Enables the header IDs Comrak extension. from the GFM spec. ""
footnotes Enables the footnotes extension per cmark-gfm. false
description_lists Enables the description lists extension. false
front_matter_delimiter Enables the front matter extension. ""
shortcodes Enables the shortcodes extension. true

For more information on these options, see the comrak documentation.

Plugins

In addition to the possibilities provided by generic CommonMark rendering, Commonmarker also supports plugins as a means of providing further niceties.

Syntax Highlighter Plugin

The library comes with a set of pre-existing themes for highlighting code:

  • "base16-ocean.dark"
  • "base16-eighties.dark"
  • "base16-mocha.dark"
  • "base16-ocean.light"
  • "InspiredGitHub"
  • "Solarized (dark)"
  • "Solarized (light)"
code = <<~CODE
  ```ruby
  def hello
    puts "hello"
  end
  ```
CODE

# pass in a theme name from a pre-existing set
puts Commonmarker.to_html(code, plugins: { syntax_highlighter: { theme: "InspiredGitHub" } })

# <pre style="background-color:#ffffff;" lang="ruby"><code>
# <span style="font-weight:bold;color:#a71d5d;">def </span><span style="font-weight:bold;color:#795da3;">hello
# </span><span style="color:#62a35c;">puts </span><span style="color:#183691;">&quot;hello&quot;
# </span><span style="font-weight:bold;color:#a71d5d;">end
# </span>
# </code></pre>

By default, the plugin uses the "base16-ocean.dark" theme to syntax highlight code.

To disable this plugin, set the value to nil:

code = <<~CODE
  ```ruby
  def hello
    puts "hello"
  end
  ```
CODE

Commonmarker.to_html(code, plugins: { syntax_highlighter: nil })

# <pre lang="ruby"><code>def hello
#   puts &quot;hello&quot;
# end
# </code></pre>

To output CSS classes instead of style attributes, set the theme key to "":

code = <<~CODE
  ```ruby
  def hello
    puts "hello"
  end
CODE

Commonmarker.to_html(code, plugins: { syntax_highlighter: { theme: "" } })

# <pre class="syntax-highlighting"><code><span class="source ruby"><span class="meta function ruby"><span class="keyword control def ruby">def</span></span><span class="meta function ruby"> # <span class="entity name function ruby">hello</span></span>
#   <span class="support function builtin ruby">puts</span> <span class="string quoted double ruby"><span class="punctuation definition string begin ruby">&quot;</span>hello<span class="punctuation definition string end ruby">&quot;</span></span>
# <span class="keyword control ruby">end</span>\n</span></code></pre>

To use a custom theme, you can provide a path to a directory containing .tmtheme files to load:

Commonmarker.to_html(code, plugins: { syntax_highlighter: { theme: "Monokai", path: "./themes" } })

Output formats

Commonmarker can currently only generate output in one format: HTML.

HTML

puts Commonmarker.to_html('*Hello* world!')

# <p><em>Hello</em> world!</p>

Developing locally

After cloning the repo:

script/bootstrap
bundle exec rake compile

If there were no errors, you're done! Otherwise, make sure to follow the comrak dependency instructions.

Benchmarks

Some rough benchmarks:

$ bundle exec rake benchmark

input size = 11064832 bytes

Warming up --------------------------------------
           redcarpet     2.000  i/100ms
commonmarker with to_html
                         1.000  i/100ms
            kramdown     1.000  i/100ms
Calculating -------------------------------------
           redcarpet     22.317  (± 4.5%) i/s -    112.000  in   5.036374s
commonmarker with to_html
                          5.815  (± 0.0%) i/s -     30.000  in   5.168869s
            kramdown      0.327  (± 0.0%) i/s -      2.000  in   6.121486s

Comparison:
           redcarpet:       22.3 i/s
commonmarker with to_html:        5.8 i/s - 3.84x  (± 0.00) slower
            kramdown:        0.3 i/s - 68.30x  (± 0.00) slower