An opinionated JSONSchema compiler for elixir.

Currently supports JSONSchema draft 0.7. except:

• integer filters do not match exact integer floating point values.
• multipleOf is not supported for the number type (don't worry, it IS supported for integers). This is because Elixir does not support a floating point remainder guard, and also because it is impossible for a floating point to guarantee sane results (e.g. for IEEE Float64, 1.2 / 0.1 != 12)
• currently remoteref is not supported.

For details, see: http://json-schema.org

Exonerate is automatically tested against the JSONSchema test suite.

Usage

Exonerate is 100% compile-time generated. You should include Exonerate with the runtime: false option in mix.exs.

In your module:

defmodule MyModule do
  require Exonerate

  Exonerate.function_from_string(:def, :function_name, """
  {
    "type": "string"
  }
  """)
end

The above module generates a function MyModule.function_name/1 that takes an erlang JSON term (string | number | array | map | bool | nil) and validates it based on the the JSONschema. If the term validates, it produces :ok. If the term fails to validate, it produces {:error, keyword}, where the key :json_pointer and points to the error location in the passed parameter, the :schema_pointers points to the validation that failed, and error_value is the failing inner term.

Metadata

The following metadata are accessible for the entrypoint in the jsonschema, by passing the corresponding atom.

Options

The following options are available:

• :format_options: a map of JSONpointers to tags with corresponding {"format" => "..."} filters. Exonerate ships with filters for the following default content:

  • date-time
  • date
  • time
  • ipv4
  • ipv6

  To disable these filters, pass false to the path, e.g. %{"/" => false} or %{"/foo/bar/" => false}. To specify a custom format filter, pass either function/args or mfa to the path, e.g. %{"/path/to/fun" => {Module, :fun, [123]}} The corresponding function will be called with the string as the first argument and the supplied arguments after. If you use the function/args (e.g. {:private_function, [123]}) it may be a private function in the same module. The custom function should return true on successful validation and false on failure. date-time ships with the parameter :utc which you may pass as %{"/path/to/date-time/" => [:utc]} that forces the date-time to be an ISO-8601 datetime string.

• :entrypoint: a JSONpointer to the internal location inside of a json document where you would like to start the JSONschema. A json document might contain multiple schemasFor example:

    multischema = """
    {
      "schema1": {"type": "string"},
      "schema2": {"type": "number"}
    }
    """
    Exonerate.function_from_string(:def, :schema1, multischema, entrypoint: "/schema1")
    Exonerate.function_from_string(:def, :schema2, multischema, entrypoint: "/schema2")

  In more practical terms, this enables you to store single documents and reuse components, especially when combined with $ref tags. Exonerate will be parsimonious and minimize producing multiple functions for validation trees so long as the instantiated functions are within the same module.