Inspired by prmd's doc generation, this is a stand-alone gem to generate Markdown files from a single JSON schema file. prmd's doc generator is rather opinionated, and I did not like its opinions. 😅


Add this line to your application's Gemfile:

gem 'json-schema-docs'

And then execute:

$ bundle

Or install it yourself as:

$ gem install json-schema-docs


# pass in a filename
JsonSchemaDocs.build(filename: filename)

# or pass in a string
JsonSchemaDocs.build(schema: contents)

# or a schema class
schema = Prmd::Schema.new(data)
JsonSchemaDocs.build(schema: schema)


There are several phases going on the single JsonSchemaDocs.build call:

  • The JSON schema file is read (if you passed filename) through Prmd::Schema (or simply consumed if you passed it through schema).
  • JsonSchemaDocs::Parser manipulates the schema into a slightly saner format.
  • JsonSchemaDocs::Generator takes that saner format and begins the process of applying items to the HTML templates.
  • JsonSchemaDocs::Renderer technically runs as part of the generation phase. It passes the contents of each page and converts it into HTML.

If you wanted to, you could break these calls up individually. For example:

options = {}
options[:filename] = "#{File.dirname(__FILE__)}/../data/schema.json"

options = JsonSchemaDocs::Configuration::JSON_SCHEMA_DOCS_DEFAULTS.merge(options)

response = File.read(options[:filename])

parser = JsonSchemaDocs::Parser.new(response, options)
parsed_schema = parser.parse

generator = JsonSchemaDocs::Generator.new(parsed_schema, options)


Generating output

By default, the generation process uses ERB to layout the content. There are a bunch of default options provided for you, but feel free to override any of these. The Configuration section below has more information on what you can change.

It also uses html-pipeline to perform the rendering by default. You can override this by providing a custom rendering class.You must implement two methods:

  • initialize - Takes two arguments, the parsed schema and the configuration options.
  • render Takes the contents of a template page. It also takes an optional kwargs, meta, for anything you want to include in your template. For example:
class CustomRenderer
  def initialize(parsed_schema, options)
    @parsed_schema = parsed_schema
    @options = options

  def render(contents, meta: {})
    contents = contents.sub(/Repository/i, '<strong>Meow Woof!</strong>')
    opts = meta.merge({ foo: "bar" })

    @default_layout.result(OpenStruct.new(opts).instance_eval { binding })

options[:filename] = 'location/to/schema.json'
options[:renderer] = CustomRenderer


If your render method returns nil, the Generator will not attempt to write any HTML file.

Helper methods

In your ERB layouts, there are several helper methods you can use. The helper methods are:

  • slugify(str): This slugifies the given string.
  • include(filename, opts): This embeds a template from your includes folder, passing along the local options provided.
  • markdownify(string): This converts a string into HTML via CommonMarker.
  • types: Collections of the various types.
  • schemata(name): The schemata defined by name.

To call these methods within templates, you must use the dot notation, such as <%= slugify.(text) %>.


The following options are available:

Option Description Default
filename The location of your schema's JSON file. nil
schema A string representing a schema JSON file. nil
output_dir The location of the output HTML files. ./output/
use_default_styles Indicates if you want to use the default styles. true
base_url Indicates the base URL to prepend for assets and links. ""
delete_output Deletes output_dir before generating content. false
pipeline_config Defines two sub-keys, pipeline and context, which are used by html-pipeline when rendering your output. The defaults are found in lib/json-schema-docs/configuration.rb/
renderer The rendering class to use. JsonSchemaDocs::Renderer
templates The templates to use when generating HTML. You may override any of the following keys: default, links, resource. The defaults are found in lib/json-schema-docs/layouts/.
landing_pages The landing page to use when generating HTML for each type. You may override any of the following keys: index. The defaults are found in lib/json-schema-docs/landing_pages/.
prmd The options to pass into PRMD's parser. The defaults are found in lib/json-schema-docs/configuration.rb/.


After checking out the repo, run script/bootstrap to install dependencies. Then, run rake test to run the tests. You can also run bundle exec rake console for an interactive prompt that will allow you to experiment.

Sample site

Clone this repository and run:

bundle exec rake sample

to see some sample output.