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A DSL for defining API schemas/endpoints, validating, serializing and generating Open API v3
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README.md

Bluepine

CircleCI

Bluepine is a DSL for defining API Schema/Endpoint with the capabilities to generate Open API (v3) spec (other specs is coming soon), validate API request and serialize object for API response based on single schema definition.

Table of Contents

Quick Start

Defining a schema

Let's start by creating a simple schema. (For a complete list of attributes and its options please see Attributes section)

A schema can be created and registered separately, or we can use Resolver to create and register in one step.

require "bluepine"

# Schema is just an `ObjectAttribute`
Bluepine::Resolver.new do

  # Defines :hero schema
  schema :hero do
    string :name, min: 4

    # recursive schema
    array   :friends, of: :hero

    # nested object
    object :stats do
      number :strength, default: 0
    end

    # reference
    schema :team
  end

  # Defines :team schema
  schema :team do
    string :name, default: "Avengers"
  end
end

Serializing schema

In order to serialize schema, we just pass schema defined in previous step to Serializer.

The object to be serialized can be a Hash or any Object with method/accessor.

hero = {
  name: "Thor",
  friends: [
    {
      name: "Iron Man",
      stats: {
        strength: "9"
      }
    }
  ],
  stats: {
    strength: "8"
  }
}

# or using our own Model class
hero = Hero.new(name: "Thor")

serializer = Bluepine::Serializer.new(resolver)
serializer.serialize(hero_schema, hero)

will produce the following result

{
  name: "Thor",
  stats: {
    strength: 8
  },
  friends: [
    { name: "Iron Man", stats: { strength: 9 }, friends: [], team: { name: "Avengers" } }
  ],
  team: {
    name: "Avengers"
  }
}

Note: It converts number to string (via Attribute.serializer) and automatically adds missing fields and default value

Validating data

To validate data against defined schema. We just pass it to Validator#validate method.

The payload could be a Hash or any Object.

payload = {
  name: "Hulk",
  friends: [
    { name: "Tony" },
    { name: "Sta"},
  ],
  team: {
    name: "Aven"
  }
}

validator = Bluepine::Validator.new(resolver)
validator.validate(user_schema, payload) # => Result

It'll return Result object which has 2 attributes #value and #errors.

In the case of errors, #errors will contain all error messages

# Result.errors =>
{
  friends: {
    1 => {
      name: ["is too short (minimum is 4 characters)"]
    }
  },
  team: {
    name: ["is too short (minimum is 5 characters)"]
  }
}

If there's no errors, #value will contain normalized data.

# Result.value =>
{
  name: "Thor",
  stats: {
    strength: 0
  },
  friends: [
    {
      name: "Iron Man",
      stats: { strength: 0 },
      friends: [],
      team: {
        name: "Avengers"
      }
    }
  ],
  team: { name: "Avengers" }
}

All default values will be added automatically.

Generating Open API (v3)

generator = Bluepine::Generators::OpenAPI::Generator.new(resolver)
generator.generate # => return Open API v3 Specification

Installation

gem 'bluepine'

And then execute:

$ bundle

Or install it yourself as:

$ gem install bluepine

Attributes

Attribute is just a simple class which doesn't have any functionality/logic on its own. With this design, it decouples the logics to validate, serialize, etc from Attribute and let's consumers (e.g. Validator, Serializer, etc) decide it instead.

Here're pre-defined attributes that we can use.

Creating Attribute

There're couple of ways to create attributes. We can create it manually or using some other methods.

Manually Creating Attribute

Here, we're creating it manually.

user_schema = Bluepine::Attributes::ObjectAttribute.new(:user) do
  string :username
  string :password
end

Using Attributes.create

This is equivalent to the above code

Bluepine::Attributes.create(:object, :user) do
  string :username
  string :password
end

Using Resolver

This is probably the easiest way to create object attribute. Since it also keeps track of the created attribute for you. (So, we don't have to register it by ourself. See also Resolver)

Bluepine::Resolver.new do
  schema :user do
    string :username
    string :password
  end
end

Array Attribute

Array attribute supports an option named :of which we can use to describe what kind of data can be contained inside array.

For example

schema :user do
  string :name

  # Indicates that each item inside must have the same structure
  # as :user schema (e.g. friends: [{ name: "a", friends: []}, ...])
  array  :friends, of: :user

  # i.e. pets: ["Joey", "Buddy", ...]
  array  :pets, of: :string

  # When nothing is given, array can contain any kind of data
  array  :others
end

Object Attribute

Most of the time, we'll be working with this attribute more often.

schema :user do
  string :name

  # nested attribute
  object :address do
    string :street

    # more nested attribute if needed
    object :country do
      string :name
    end
  end
end

Schema Attribute

Instead of declaring a lot of nested object. We can also use schema attribute to refer to other previously defined schema (DRY).

It also accepts :of option. (it works the same as Array)

schema :hero do
  string :name

  # This implies `of: :team`
  schema :team

  # If the field name is different, we can specify `:of` option (which work the same way as `Array`)
  schema :awesome_team, of: :team
end

schema :team do
  string :name
end

Attribute Options

All attributes have common set of options avaiable

Name type Description Serializer Validator Open API
name string|symbol Attribute's name e.g. email
method symbol When attribute's name differs from target's name, we can use this to specify a method that will be used to get the value for the attribute. read value from specified name instead. See Serializer :method.
match Regexp Regex that will be used to validate the attribute's value (string attribute) validates string based on given Regexp Will add Regexp to generated pattern property
type string Data type Attribute's type e.g. string, schema etc
native_type string JSON's data type
format string|symbol describes the format of this value. Could be arbitary value e.g. int64, email etc. This'll be added to format property
of symbol specifies what type of data will be represented in array. The value could be attribute type e.g. :string or other schema e.g. :user serializes data using specified value. See Serializer :of validates data using specified value Create a $ref type schema
in array A set of valid options e.g. %w[thb usd ...] payload value must be in this list adds to enum property
if/unless symbol|proc Conditional validating/serializing result serializes only when the specified value evalulates to true. See Serializer :if/:unless validates only when it evalulates to true
required boolean Indicates this attribute is required (for validation). Default is false makes it mandatory adds to required list
default any Default value for attribute uses as default value when target's value is nil populates as default value when it's not defined in payload adds to default property
private boolean marks it as private. Default is false Excludes this attribute from serialized value
deprecated boolean marks this attribute as deprecated. Default is false adds to deprecated property
description string Description of attribute
spec string Specification of the value (for referencing only)
spec_uri string URI of spec

Custom Attribute

If you want to add your own custom attribute. Simply create a new class and make it extends from Attribute and then register it to Attributes registry.

class AwesomeAttribute < Bluepine::Attributes::Attribute
  # codes ...
end

# Register it
Bluepine::Attributes.register(:awesome, AwesomeAttribute)

Later, we can refer to it like the following.

schema :user do
  string  :email
  awesome :cool  # our custom attribute
end

Resolver

Resolver acts as a registry that holds references to all schemas and endpoints that we've defined.

Manually registering schema/endpoint

user_schema = create_user_schema

# pass it to the constructor
resolver = Bluepine::Resolver.new(schemas: [user_schema], endpoints: [])

# or use `#schemas` method
resolver.schemas.register(:user, user_schema)

Automatically registering schema/endpoint

Although we can create a schema and register it manually. It'll become a tedious tasks when there're lot of schemas/endpoints to work with.

resolver = Bluepine::Resolver.new do

  # schema is just `ObjectAttribute`
  schema :user do
    # codes
  end

  schema :group do
    # codes
  end

  endpoint "/users" do
    # codes
  end
end

Serialization

Serializer was designed in the way that it can serialize any type of Attribute. Either it's simple attribute type such as StringAttribute or a more complex type like ObjectAttribute. The Serializer treats it the same way.

Example

Serializing a simple type

attr = Bluepine::Attributes.create(:string, :email)

serializer.serialize(attr, 3.14) # => "3.14"

Serializing Array

attr = Bluepine::Attributes.create(:array, :heroes)

serializer.serialize(attr, ["Iron Man", "Thor"]) # => ["Iron Man", "Thor"]

Serializing Object

When serializing object, the data that we want to serialize can be a Hash or plain Object.

In the following example. We serialize an instance of Hero class.

attr = Bluepine::Attributes.create(:object, :hero) do
  string :name
  number :power, default: 5
end

# Defines our class
class Hero
  attr_reader :name, :power

  def initialize(name:, power: nil)
    @name  = name
    @power = power
  end

  def name
    "I'm #{@name}"
  end
end

thor = Hero.new(name: "Thor")

# Serializes
serializer.serialize(attr, thor) # =>

{
  name: "I'm Thor",
  power: 5
}

Options

:method

Value: Symbol - Alternative method name

We can use this option to specify which method of the target object that will be used to get the data from.

# Our schema
schema :hero do
  string :name, method: :awesome_name
end

class Hero
  def initialize(name)
    @name = name
  end

  def awesome_name
    "I'm super #{@name}!"
  end
end

hero = Hero.new(name: "Thor")

# Serializes
serializer.serialize(hero_schema, hero)

will produce the following result.

{
  "name": "I'm super Thor!"
}

:of

Value: Symbol - Attribute type or Schema name e.g. :string or :user

This option allows us to refer to other schema from array or schema attribute.

In the following example. We'll re-use our previously defined :hero schema with our new :team schema.

schema :team do
  array :heroes, of: :hero
end

class Team
  attr_reader :name, :heroes

  def initialize(name: name, heroes: heroes)
    @name   = name
    @heroes = heroes
  end
end

team = Team.new(name: "Avengers", heroes: [
  Hero.new(name: "Thor"),
  Hero.new(name: "Hulk", power: 10),
])

# Serializes
serializer.serialize(team_schema, team)

will produce the following result

{
  name: "Avengers",
  heroes: [
    { name: "Thor", power: 5 }, # 5 is default value from hero schema
    { name: "Hulk", power: 10 },
  ]
}

:private

Value: Boolean - Default is false

When it's set to true. It'll exclude that attribute from serializer's result.

schema :hero do
  string :name
  number :secret_power, private: true
end

hero = Hero.new(name: "Peter", secret_power: 99)
serializer.serialize(hero_schema, hero)

will exclude secret_power from result

{
  name: "Peter"
}

Conditional Serialization

:if/:unless

Possible value: Symbol/Proc

This enables us to serialize value based on if/unless conditions.

schema :hero do
  string :name

  # :mode'll get serialized only when `dog_dead` is true
  string :mode, if: :dog_dead

  # or we can use `Proc` e.g.
  # string :mode, if: ->(x) { x.dog_dead }
  boolean :dog_dead, default: false
end

hero = Hero.new(name: "John Wick", mode: "Angry")
serializer.serialize(hero_schema, hero) # =>

will produce

{
  name: "John Wick",
  dog_dead: false
}

But if we set dog_dead: true the result will include mode value.

{
  name: "John Wick",
  mode: "Angry",
  dog_dead: true,
}

Custom Serializer

By default, each primitive types e.g. string, integer, etc. has its own serializer. We can override it by overriding .serializer class method.

For example. If we want to extend boolean attribute to treat "on" as a valid boolean value. We could do it like this.

BooleanAttribute.normalize = ->(x) { ["on", true].include?(x) ? true : false }

# Usage
schema :team do
  boolean :active
end

team = Team.new(active: "on")
serializer.serialize(team_schema, team)

will produce

{
  active: true
}

Endpoint

Endpoint represents the API endpoint and it's operations e.g. GET, POST, etc. It groups resource's related operations together and defines a set of valid parameters that the endpoint accepts.

Defining Endpoint

We could define it manually as follows

Bluepine::Endpoint.new "/users" do
  get :read, path: "/:id"
end

or defines it via Resolver

Bluepine::Resolver.new do
  endpoint "/heroes" do
    post :create, path: "/"
  end

  endpoint "/teams" do
    # code
  end
end

Method

Endpoint provides a set of http methods such as get, post, patch, delete, etc. Each method expects a name and some other options.

Note that name must be unique within endpoint

method(name, path:, params:)

# e.g.
get  :read,   path: "/:id"
post :create, path: "/"

Params

Params allows us to define a set of valid parameters accepted by the Endpoint's methods (e.g. get, post, etc).

We can think of Params the same way as Schema (i.e. ObjectAttribute). It's just a specialize version of ObjectAttribute.

Defining default params

endpoint "/users" do
  # declare default params
  params do
    string :username
    string :password
  end

  # `params: true` will use default params for validating incoming request
  post  :create, params: true

  # this will re-use `username` param from default params
  patch :update, params: %i[username]
end

Using no params params: false (default behaviour)

If we don't want our endpoint's method to re-use default params. We can specify params: false to endpoint method's arguments.

Note: this is the default behaviour. So we can leave it blank.

get :index, path: "/" # ignore `params` means `params: false`

Using default params params: true

As we've seen in the example above. Set params: true indicates that we want to use default params for this method.

post :create, path: "/", params: true

Using subset of default params's attributes params: %i[...]

Let's say we want to use only some of default params's attrbiute e.g. currency (but not other attributes). We can specify it like this.

patch :update, path: "/:id", params: %i[currency]

In this case it will re-use only currency attribute for validation.

Excluding some of default params's attributes exclude: true

Let's say the update method doesn't need the default params's amount attribute (but still want to use all other attributes). We can specify it as follows.

patch :update, path: "/:id", params: %i[amount], exclude: true

Overriding default params with params: Proc

In the case where we want to completely use the new set of params. We can use Proc to define it like the following.

# inside schema.endpoint block
patch :update, path: "/:id", params: lambda {
  integer :max_amount, required: true
  string  :new_currency, match: /\A[a-z]{3}\z/
}

It will use these new params for validating/generating specs.

Re-using Params from Other Service params: Symbol

We can also re-use params from other endpoint by specifing a Symbol that refers to other endpoint's params.

endpoint "/search" do
  params do
    string :query
    number :limit
  end
end

endpoint "/blogs" do
  get :index, path: "/", params: :search
end

Here we will use search endpoint's default params for validating GET /users endpoint.

Endpoint Validation

See Validation - Validating Endpoint

Validation

Once we have our schema/endpoint defined. We can use validator to validate it against any data. (it uses ActiveModel::Validations under the hood)

Similar to Serializer. We can use Validator to validate any type of Attribute.

Example

Validating simple attribute

attr  = Bluepine::Attributes.create(:string, :email)
email = true

validator.validate(attr, email) # => Result object

In this case, it'll just return a Result.errors which contain error message

["is not string"]

Validating Array

attr  = Bluepine::Attributes.create(:array, :names, of: :string)
names = ["john", 1, "doe"]

validator.validate(attr, names) # => Result object

It'll return the error messages at exact index position.

{
  1 => ["is not string"]
}

Validating Object

Most of the time, we'll work with the object type (instead of simple type like string, etc).

attr  = Bluepine::Attributes.create(:object, :user) do
  string :username, min: 4
  string :password, min: 10
end

user = {
  username: "john",
  password: true,
}

validator.validate(attr, user) # => Result object

Since it's an object, the errors will contain attribute names

{
  password: [
    "is not string",
    "is too short (minimum is 10 characters)"
  ]
}

Options

:required

Value: Boolean - Default is false

This option makes the attribute mandatory.

schema :hero do
  string :name, required: true
end

hero = Hero.new
validator.validate(hero_schema, hero) # => Result.errors

will return

{
  name: ["can't be blank"]
}

:match

Value: Regexp - Regular Expression to be tested.

This option will test if string matches against given regular expression or not.

schema :hero do
  string :name, match: /\A[a-zA-Z]+\z/
end

hero = Hero.new(name: "Mark 3")
validator.validate(hero_schema, hero) # => Result.errors

will return

{
  name: ["is not valid"]
}

:min/:max

Value: Number - Apply to both string and number attribute types.

This option sets a minimum and maximum value for attribute.

schema :hero do
  string :power, max: 100
end

hero = Hero.new(power: 200)
validator.validate(hero_schema, hero) # => Result.errors

will return

{
  power: ["must be less than or equal to 100"]
}

:in

Value: Array - Set of valid values.

This option will test if value is in the specified list or not.

schema :hero do
  string :status, in: ["Happy", "Angry"]
end

hero = Hero.new(status: "Mad")
validator.validate(hero_schema, hero) # => Result.errors

will return

{
  status: ["is not included in the list"]
}

Conditional Validation

:if/:unless

Possible value: Symbol/Proc

This enables us to validate attribute based on if/unless conditions.

schema :hero do
  string :name

  # or we can use `Proc` e.g.
  # if: ->(x) { x.is_agent }
  string :agent_name, required: true, if: :is_agent

  boolean :agent, default: false
end

hero = Hero.new(name: "Nick Fury", is_agent: true)
validator.validate(hero_schema, hero) # Result.errors =>

will produce (because is_agent is true)

{
  agent_name: ["can't be blank"]
}

Custom Validator

Since the validator is based on ActiveModel::Validations. This make it easy to add a new custom validator.

In the following example. We create a simple password validator and register it to the password attribute.

# Defines custom validator
class CustomPasswordValidator < ActiveModel::Validator
  def validate(record)
    record.errors.add(:password, "is too short") unless record.password.length > 10
  end
end

# Registers
schema :user do
  string :username
  string :password, validators: [CustomPasswordValidator]
end

Custom Normalizer

It's possible to change the logic for normalizing data before passing it to the validator. For example, you might want to normalize boolean value before validating it.

Here, we want to normalize string such as on or 1 to boolean true first.

# Overrides default normalizer
BooleanAttribute.normalizer = ->(x) { [true, 1, "on"].include?(x) ? true : false }

schema :hero do
  boolean :berserk
end

hero = Hero.new(berserk: 1)
validator.validate(hero_schema, hero) # Result.value

will pass the validation and Result.value'll contain normalized value

{
  berserk: true # convert 1 to true
}

Validating Endpoint

All examples above also apply to endpoint's parameters validation.

Because the params is part of Endpoint and it's non-trivial task to retrieve endpoint's method's params. So, the Endpoint provides some helper methods to validate the data.

resolver = Bluepine::Resolver.new do
  endpoint "/heroes" do
    post :create, params: lambda {
      string :name, required: true
    }
  end
end

# :create is a POST method name given to the endpoint.
resolver.endpoint(:heroes).method(:create, resolver: resolver).validate(payload) # => Result

Generating Open API (v3)

Once we have all schemas/endpoints defined and registered to the Resolver. We can simply pass it to the generator as follows.

generator = Bluepine::Generators::OpenAPI::Generator.new(resolver, options)
generator.generate # =>

will output Open API (v3) specs

excerpt from the full result

  // endpoints
  "/users": {
    "post": {
      "requestBody": {
        "content": {
          "application/x-www-form-urlencoded": {
            "schema": {
              "type": "object",
              "properties": {
                "username": {
                  "type": "string"
                },
                "accepted": {
                  "type": "boolean",
                  "enum": [true, false]
                },
              }
            }
          }
        }
      },
      "responses": {
        "200": {
          "content": {
            "application/json": {
              "schema": {
                "$ref": "#/components/schemas/user"
              }
            }
          }
        }
      }
    }
  }

  // schema
  "user": {
    "type": "object",
    "properties": {
      "address": {
        "type": "object",
        "properties": {
          "city": {
            "type": "string",
            "default": "Bangkok"
          }
        }
      },
      "friends": {
        "type": "array",
        "items": {
          "$ref": "#/components/schemas/user"
        }
      }
    }
  }

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/omise/bluepine. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

The gem is available as open source under the terms of the MIT License.

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