Absinthe Constraints

An absinthe library to add type constraints to your GraphQL schema using directives.

Installation

Install from Hex.pm

def deps do
  [
    {:absinthe_constraints, "~> 0.3.0"}
  ]
end

Usage

1. Add use AbsintheConstraints to your schema

defmodule MyAppWeb.Schema do
  use Absinthe.Schema
  use AbsintheConstraints

  # Use `import_sdl`, etc...
end

This registers the @constraints directive both for runtime validation and as a directive declaration in the schema's blueprint. The declaration is then included in mix absinthe.schema.sdl output, so the generated SDL is valid GraphQL that downstream tooling (e.g. graphql-inspector, graphql-js) can parse.

Older versions of this library recommended setting @prototype_schema AbsintheConstraints.Directive directly. That still works at runtime but omits the directive declaration from SDL output, producing invalid GraphQL. Prefer use AbsintheConstraints.

2. Add the document phase to your absinthe Pipeline

Example using Absinthe.Plug:

# Somewhere in your router

def my_pipeline(config, opts) do
  config
  |> Absinthe.Plug.default_pipeline(opts)
  |> AbsintheConstraints.Phase.add_to_pipeline(opts)
end

forward("/", Absinthe.Plug, schema: MyAppWeb.Schema, pipeline: {__MODULE__, :my_pipeline})

3. Add constraints to your schema

# Somewhere in your schema

# Adding constraints to input object's fields
input_object :coordinates do
  field(:latitude, non_null(:float), directives: [constraints: [min: -90, max: 90]])
  field(:longitude, non_null(:float), directives: [constraints: [min: -180, max: 180]])
end

# Adding constraints to query field's arguments
object :my_queries do
  field :my_field, non_null(:string) do
    arg(:id, non_null(:string), directives: [constraints: [format: "uuid"]])
    resolve(&my_resolver/2)
  end
end

Supported constraints

String

min_length

directives: [constraints: [min_length: 5]] Restrict to a minimum length

max_length

directives: [constraints: [max_length: 5]] Restrict to a maximum length

format

directives: [constraints: [format: "uuid"]] Ensure value is in a particular format

Supported formats:

• "uuid" - uses :elixir_uuid to validate the value
• "email" - uses a regex to validate the value

pattern

directives: [constraints: [pattern: "^[A-Z][0-9a-z]*$"]] Ensure value follows a specific Regex pattern

Number (integer/float)

min

directives: [constraints: [min: 5]] Ensure value is greater than or equal to

max

directives: [constraints: [max: 5]] Ensure value is less than or equal to

List

min_items

directives: [constraints: [min_items: 5]] Restrict to a minimum number of items

max_items

directives: [constraints: [max_items: 5]] Restrict to a maximum number of items