loading a json schema including fragments

In the end I had to do this myself. Since all the fragments are of the same format, the following was possible:

  def read_schema(filename)
    reader = JSON::Schema::Reader.new(
      accept_uri: false,
      accept_file: true
    )
    schema = reader.read("#{Rails.root}/lib/record_schemas/#{filename}").schema
    return schema unless schema.has_key?('properties')

    schema['properties'].each_key do |key|
      fragment = schema['properties'].dig(key, 'items')
      next unless fragment

      ref = fragment['$ref']
      next unless ref

      next unless ref.start_with?('fragments/')

      file, type = ref.split('#')

      unless schema.has_key?('definitions')
        schema['definitions'] = {}
      end
      schema['definitions'][type] = read_fragment(file, type)
      schema['properties'][key]['items']['$ref'] = "#/definitions/#{type}"
    end
    schema
  end

  def read_fragment(file, key)
    reader = JSON::Schema::Reader.new(
        accept_uri: false,
        accept_file: true
    )
    schema = reader.read("#{Rails.root}/lib/record_schemas/#{file}").schema
    schema['definitions'][key]
  end

This looks for any references to a fragment in a schema and, if it finds one, converts the reference to an internal one and loads the fragment’s definition into the schema.