GitHub HTML processing filters and utilities. This module includes a small framework for defining DOM based content filters and applying them to user provided content. Read an introduction about this project in this blog post.
Add this line to your application's Gemfile:
gem 'html-pipeline'And then execute:
$ bundleOr install it yourself as:
$ gem install html-pipelineThis library provides a handful of chainable HTML filters to transform user
content into markup. A filter takes an HTML string or
Nokogiri::HTML::DocumentFragment, optionally manipulates it, and then
outputs the result.
For example, to transform Markdown source into Markdown HTML:
require 'html/pipeline'
filter = HTML::Pipeline::MarkdownFilter.new("Hi **world**!")
filter.callFilters can be combined into a pipeline which causes each filter to hand its output to the next filter's input. So if you wanted to have content be filtered through Markdown and be syntax highlighted, you can create the following pipeline:
pipeline = HTML::Pipeline.new [
HTML::Pipeline::MarkdownFilter,
HTML::Pipeline::SyntaxHighlightFilter
]
result = pipeline.call <<-CODE
This is *great*:
some_code(:first)
CODE
result[:output].to_sPrints:
<p>This is <em>great</em>:</p>
<div class="highlight">
<pre><span class="n">some_code</span><span class="p">(</span><span class="ss">:first</span><span class="p">)</span>
</pre>
</div>Some filters take an optional context and/or result hash. These are used to pass around arguments and metadata between filters in a pipeline. For example, if you want don't want to use GitHub formatted Markdown, you can pass an option in the context hash:
filter = HTML::Pipeline::MarkdownFilter.new("Hi **world**!", :gfm => false)
filter.callMentionFilter- replace@usermentions with linksAbsoluteSourceFilter- replace relative image urls with fully qualified versionsAutoLinkFilter- auto_linking urls in HTMLCamoFilter- replace http image urls with camo-fied https versionsEmailReplyFilter- util filter for working with emailsEmojiFilter- everyone loves emoji!HttpsFilter- HTML Filter for replacing http github urls with https versions.ImageMaxWidthFilter- link to full size image for large imagesMarkdownFilter- convert markdown to htmlPlainTextInputFilter- html escape text and wrap the result in a divSanitizationFilter- whitelist sanitize user markupSyntaxHighlightFilter- code syntax highlighterTextileFilter- convert textile to htmlTableOfContentsFilter- anchor headings with name attributes
SyntaxHighlightFilter uses github-linguist
to detect and highlight languages. It isn't included as a dependency by default
because it's a large dependency and
a hassle to build on heroku.
To use the filter, add the following to your Gemfile:
gem 'github-linguist'We define different pipelines for different parts of our app. Here are a few paraphrased snippets to get you started:
# The context hash is how you pass options between different filters.
# See individual filter source for explanation of options.
context = {
:asset_root => "http://your-domain.com/where/your/images/live/icons",
:base_url => "http://your-domain.com"
}
# Pipeline providing sanitization and image hijacking but no mention
# related features.
SimplePipeline = Pipeline.new [
SanitizationFilter,
TableOfContentsFilter, # add 'name' anchors to all headers
CamoFilter,
ImageMaxWidthFilter,
SyntaxHighlightFilter,
EmojiFilter,
AutolinkFilter
], context
# Pipeline used for user provided content on the web
MarkdownPipeline = Pipeline.new [
MarkdownFilter,
SanitizationFilter,
CamoFilter,
ImageMaxWidthFilter,
HttpsFilter,
MentionFilter,
EmojiFilter,
SyntaxHighlightFilter
], context.merge(:gfm => true) # enable github formatted markdown
# Define a pipeline based on another pipeline's filters
NonGFMMarkdownPipeline = Pipeline.new(MarkdownPipeline.filters,
context.merge(:gfm => false))
# Pipelines aren't limited to the web. You can use them for email
# processing also.
HtmlEmailPipeline = Pipeline.new [
ImageMaxWidthFilter
], {}
# Just emoji.
EmojiPipeline = Pipeline.new [
HTMLInputFilter,
EmojiFilter
], contextTo write a custom filter, you need a class with a call method that inherits
from HTML::Pipeline::Filter.
For example this filter adds a base url to images that are root relative:
require 'uri'
class RootRelativeFilter < HTML::Pipeline::Filter
def call
doc.search("img").each do |img|
next if img['src'].nil?
src = img['src'].strip
if src.start_with? '/'
img["src"] = URI.join(context[:base_url], src).to_s
end
end
doc
end
endNow this filter can be used in a pipeline:
Pipeline.new [ RootRelativeFilter ], { :base_url => 'http://somehost.com' }Filters and Pipelines can be set up to be instrumented when called. The pipeline
must be setup with an [ActiveSupport::Notifications]
(http://api.rubyonrails.org/classes/ActiveSupport/Notifications.html)
compatible service object and a name. New pipeline objects will default to the
HTML::Pipeline.default_instrumentation_service object.
# the AS::Notifications-compatible service object
service = ActiveSupport::Notifications
# instrument a specific pipeline
pipeline = HTML::Pipeline.new [MarkdownFilter], context
pipeline.setup_instrumentation "MarkdownPipeline", service
# or set default instrumentation service for all new pipelines
HTML::Pipeline.default_instrumentation_service = service
pipeline = HTML::Pipeline.new [MarkdownFilter], context
pipeline.setup_instrumentation "MarkdownPipeline"Filters are instrumented when they are run through the pipeline. A
call_filter.html_pipeline event is published once the filter finishes. The
payload should include the filter name. Each filter will trigger its own
instrumentation call.
service.subscribe "call_filter.html_pipeline" do |event, start, ending, transaction_id, payload|
payload[:pipeline] #=> "MarkdownPipeline", set with `setup_instrumentation`
payload[:filter] #=> "MarkdownFilter"
payload[:context] #=> context Hash
payload[:result] #=> instance of result class
payload[:result][:output] #=> output HTML String or Nokogiri::DocumentFragment
endThe full pipeline is also instrumented:
service.subscribe "call_pipeline.html_pipeline" do |event, start, ending, transaction_id, payload|
payload[:pipeline] #=> "MarkdownPipeline", set with `setup_instrumentation`
payload[:filters] #=> ["MarkdownFilter"]
payload[:doc] #=> HTML String or Nokogiri::DocumentFragment
payload[:context] #=> context Hash
payload[:result] #=> instance of result class
payload[:result][:output] #=> output HTML String or Nokogiri::DocumentFragment
endFull reference documentation can be found here.
To see what has changed in recent versions, see the CHANGELOG.
bundle
rake test- Fork it
- Create your feature branch (
git checkout -b my-new-feature) - Commit your changes (
git commit -am 'Added some feature') - Push to the branch (
git push origin my-new-feature) - Create new Pull Request
Thanks to all of these contributors.
Project is a member of the OSS Manifesto.
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