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# Open API Spex
[![Build Status](https://travis-ci.com/open-api-spex/open_api_spex.svg?branch=master)](https://travis-ci.com/open-api-spex/open_api_spex)
[![Hex.pm](https://img.shields.io/hexpm/v/open_api_spex.svg)](https://hex.pm/packages/open_api_spex)
Leverage Open API Specification 3 (formerly Swagger) to document, test, validate and explore your Plug and Phoenix APIs.
- Generate and serve a JSON Open API Spec document from your code
- Use the spec to cast request params to well defined schema structs
- Validate params against schemas, eliminate bad requests before they hit your controllers
- Validate responses against schemas in tests, ensuring your docs are accurate and reliable
- Explore the API interactively with with [SwaggerUI](https://swagger.io/swagger-ui/)
Full documentation available on [hexdocs](https://hexdocs.pm/open_api_spex/)
## Installation
The package can be installed by adding `open_api_spex` to your list of dependencies in `mix.exs`:
```elixir
def deps do
[
{:open_api_spex, "~> 3.6"}
]
end
```
## Generate Spec
### Main Spec
Start by adding an `ApiSpec` module to your application to populate an `OpenApiSpex.OpenApi` struct.
```elixir
defmodule MyAppWeb.ApiSpec do
alias OpenApiSpex.{Components, Info, OpenApi, Paths, Server}
alias MyAppWeb.{Endpoint, Router}
@behaviour OpenApi
@impl OpenApi
def spec do
%OpenApi{
servers: [
# Populate the Server info from a phoenix endpoint
Server.from_endpoint(Endpoint)
],
info: %Info{
title: "My App",
version: "1.0"
},
# Populate the paths from a phoenix router
paths: Paths.from_router(Router)
}
|> OpenApiSpex.resolve_schema_modules() # Discover request/response schemas from path specs
end
end
```
Or you can use application's spec value in `info:` key.
```elixir
info: %Info{
description: Application.spec(:my_app, :description)
version: Application.spec(:my_app, :vsn)
}
```
### Authorization
In case your API requires authorization you can add security schemes as part of the components in the main spec.
```elixir
components: %Components{
securitySchemes: %{authorization: %SecurityScheme{type: "http", scheme: "bearer"}}
}
```
Once the security scheme is defined you can declare it. Please note that the key below matches the one defined in the security scheme, in the our example, `authorization`.
```elixir
security: [%{authorization: []}]
```
If you require authorization for all endpoints you can declare the `security` in the main spec. In case you need authorization only for specific endpoints, or if you are using more than one security scheme, you can declare it as part of each operation.
To learn more about the different security schemes please the check the [official documentation](https://swagger.io/docs/specification/authentication/).
### Operations
For each plug (controller) that will handle api requests, add an `open_api_operation` callback.
It will be passed the plug opts that were declared in the router, this will be the action for a phoenix controller. The callback populates an `OpenApiSpex.Operation` struct describing the plug/action.
```elixir
defmodule MyAppWeb.UserController do
alias OpenApiSpex.Operation
alias MyAppWeb.Schemas.UserResponse
@spec open_api_operation(atom) :: Operation.t()
def open_api_operation(action) do
operation = String.to_existing_atom("#{action}_operation")
apply(__MODULE__, operation, [])
end
@spec show_operation() :: Operation.t()
def show_operation() do
%Operation{
tags: ["users"],
summary: "Show user",
description: "Show a user by ID",
operationId: "UserController.show",
parameters: [
Operation.parameter(:id, :path, :integer, "User ID", example: 123, required: true)
],
responses: %{
200 => Operation.response("User", "application/json", UserResponse)
}
}
end
# Controller's `show` action
def show(conn, %{id: id}) do
{:ok, user} = MyApp.Users.find_by_id(id)
json(conn, 200, user)
end
end
```
Alternatively, you can create an operation file separately using `defdelegate`.
```elixir
# Phoenix's controller
defmodule MyAppWeb.UserController do
defdelegate open_api_operation(action), to: MyAppWeb.UserApiOperation
def show(conn, %{id: id}) do
{:ok, user} = MyApp.Users.find_by_id(id)
json(conn, 200, user)
end
end
# Open API Spex operations
defmodule MyAppWeb.UserApiOperation do
alias OpenApiSpex.Operation
alias MyAppWeb.Schemas.UserResponse
@spec open_api_operation(atom) :: Operation.t()
def open_api_operation(action) do
operation = String.to_existing_atom("#{action}_operation")
apply(__MODULE__, operation, [])
end
@spec show_operation() :: Operation.t()
def show_operation() do
%Operation{
tags: ["users"],
summary: "Show user",
description: "Show a user by ID",
operationId: "UserController.show",
parameters: [
Operation.parameter(:id, :path, :integer, "User ID", example: 123, required: true)
],
responses: %{
200 => Operation.response("User", "application/json", UserResponse)
}
}
end
end
```
For examples of other action operations, see the
[example web app](https://github.com/open-api-spex/open_api_spex/blob/master/examples/phoenix_app/lib/phoenix_app_web/controllers/user_controller.ex).
### Schemas
Next, declare JSON schema modules for the request and response bodies.
In each schema module, call `OpenApiSpex.schema/1`, passing the schema definition. The schema must
have keys described in `OpenApiSpex.Schema.t`. This will define a `%OpenApiSpex.Schema{}` struct.
This struct is made available from the `schema/0` public function, which is generated by `OpenApiSpex.schema/1`.
You may optionally have the data described by the schema turned into a struct linked to the JSON schema by adding `"x-struct": __MODULE__`
to the schema.
```elixir
defmodule MyAppWeb.Schemas do
alias OpenApiSpex.Schema
defmodule User do
require OpenApiSpex
OpenApiSpex.schema(%{
title: "User",
description: "A user of the app",
type: :object,
properties: %{
id: %Schema{type: :integer, description: "User ID"},
name: %Schema{type: :string, description: "User name", pattern: ~r/[a-zA-Z][a-zA-Z0-9_]+/},
email: %Schema{type: :string, description: "Email address", format: :email},
birthday: %Schema{type: :string, description: "Birth date", format: :date},
inserted_at: %Schema{
type: :string,
description: "Creation timestamp",
format: :"date-time"
},
updated_at: %Schema{type: :string, description: "Update timestamp", format: :"date-time"}
},
required: [:name, :email],
example: %{
"id" => 123,
"name" => "Joe User",
"email" => "joe@gmail.com",
"birthday" => "1970-01-01T12:34:55Z",
"inserted_at" => "2017-09-12T12:34:55Z",
"updated_at" => "2017-09-13T10:11:12Z"
}
})
end
defmodule UserResponse do
require OpenApiSpex
OpenApiSpex.schema(%{
title: "UserResponse",
description: "Response schema for single user",
type: :object,
properties: %{
data: User
},
example: %{
"data" => %{
"id" => 123,
"name" => "Joe User",
"email" => "joe@gmail.com",
"birthday" => "1970-01-01T12:34:55Z",
"inserted_at" => "2017-09-12T12:34:55Z",
"updated_at" => "2017-09-13T10:11:12Z"
}
}
})
end
end
```
For more examples of schema definitions, see the
[sample Phoenix app](https://github.com/open-api-spex/open_api_spex/blob/master/examples/phoenix_app/lib/phoenix_app_web/schemas.ex)
## Serve the Spec
To serve the API spec from your application, first add the `OpenApiSpex.Plug.PutApiSpec` plug somewhere in the pipeline.
```elixir
pipeline :api do
plug OpenApiSpex.Plug.PutApiSpec, module: MyAppWeb.ApiSpec
end
```
Now the spec will be available for use in downstream plugs.
The `OpenApiSpex.Plug.RenderSpec` plug will render the spec as JSON:
```elixir
scope "/api" do
pipe_through :api
resources "/users", MyAppWeb.UserController, only: [:create, :index, :show]
get "/openapi", OpenApiSpex.Plug.RenderSpec, []
end
```
## Generating the Spec
Optionally, you can create a mix task to write the swagger file to disk:
```elixir
defmodule Mix.Tasks.MyApp.OpenApiSpec do
def run([output_file]) do
MyAppWeb.Endpoint.start_link() # Required if using for OpenApiSpex.Server.from_endpoint/1
json =
MyAppWeb.ApiSpec.spec()
|> Jason.encode!(pretty: true)
:ok = File.write!(output_file, json)
end
end
```
Generate the file with: `mix my_app.openapispec spec.json`
## Serve Swagger UI
Once your API spec is available through a route (see "Serve the Spec"), the `OpenApiSpex.Plug.SwaggerUI` plug can be used to
serve a SwaggerUI interface. The `path:` plug option must be supplied to give the path to the API spec.
All JavaScript and CSS assets are sourced from cdnjs.cloudflare.com, rather than vendoring into this package.
```elixir
scope "/" do
pipe_through :browser # Use the default browser stack
get "/", MyAppWeb.PageController, :index
get "/swaggerui", OpenApiSpex.Plug.SwaggerUI, path: "/api/openapi"
end
scope "/api" do
pipe_through :api
resources "/users", MyAppWeb.UserController, only: [:create, :index, :show]
get "/openapi", OpenApiSpex.Plug.RenderSpec, []
end
```
## Importing an existing schema file
> :warning: This functionality currently converts Strings into Atoms, which makes it potentially [vulnerable to DoS attacks](https://til.hashrocket.com/posts/gkwwfy9xvw-converting-strings-to-atoms-safely). We recommend that you load Open API Schemas from *known files* during application startup and *not dynamically from external sources at runtime*.
OpenApiSpex has functionality to import an existing schema, casting it into an %OpenApi{} struct. This means you can load a schema that is JSON or YAML encoded. See the example below:
```elixir
# Importing an existing JSON encoded schema
open_api_spec_from_json = "encoded_schema.json"
|> File.read!()
|> Jason.decode!()
|> OpenApiSpex.OpenApi.Decode.decode()
# Importing an existing YAML encoded schema
open_api_spec_from_yaml = "encoded_schema.yaml"
|> YamlElixir.read_all_from_file!()
|> OpenApiSpex.OpenApi.Decode.decode()
```
You can then use the loaded spec to with `OpenApiSpex.cast_and_validate/4`, like:
```elixir
{:ok, _} = OpenApiSpex.cast_and_validate(
open_api_spec_from_json, # or open_api_spec_from_yaml
spec.paths["/some_path"].post,
test_conn,
"application/json"
)
```
## Validating and Casting Params
OpenApiSpex can automatically validate requests before they reach the controller action function. Or if you prefer,
you can explicitly call on OpenApiSpex to cast and validate the params within the controller action. This section
describes the former.
First, the `plug OpenApiSpex.Plug.PutApiSpec` needs to be called in the Router, as described above.
Add the `OpenApiSpex.Plug.CastAndValidate` plug to a controller to validate request parameters and to cast to Elixir types defined by the operation schema.
```elixir
# Phoenix
plug OpenApiSpex.Plug.CastAndValidate
# Plug
plug OpenApiSpex.Plug.CastAndValidate, operation_id: "UserController.create
```
For Phoenix apps, the `operation_id` can be inferred from the contents of `conn.private`.
```elixir
defmodule MyAppWeb.UserController do
use MyAppWeb, :controller
alias OpenApiSpex.Operation
alias MyAppWeb.Schemas.{User, UserRequest, UserResponse}
plug OpenApiSpex.Plug.CastAndValidate
def open_api_operation(action) do
apply(__MODULE__, :"#{action}_operation", [])
end
def create_operation do
import Operation
%Operation{
tags: ["users"],
summary: "Create user",
description: "Create a user",
operationId: "UserController.create",
parameters: [
parameter(:id, :query, :integer, "user ID")
],
requestBody: request_body("The user attributes", "application/json", UserRequest),
responses: %{
201 => response("User", "application/json", UserResponse)
}
}
end
def create(conn = %{body_params: %UserRequest{user: %User{name: name, email: email, birthday: birthday = %Date{}}}}, %{id: id}) do
# conn.body_params cast to UserRequest struct
# conn.params.id cast to integer
end
end
```
Now the client will receive a 422 response whenever the request fails to meet the validation rules from the api spec.
The response body will include the validation error message:
```json
{
"errors": [
{
"message": "Invalid format. Expected :date",
"source": {
"pointer": "/data/birthday"
},
"title": "Invalid value"
}
]
}
```
See also `OpenApiSpex.cast_value/3` for casting and validating outside of a `plug` pipeline.
## Validate Examples
As schemas evolve, you may want to confirm that the examples given match the schemas.
Use the `OpenApiSpex.TestAssertions` module to assert on schema validations.
```elixir
use ExUnit.Case
import OpenApiSpex.TestAssertions
test "UsersResponse example matches schema" do
api_spec = MyAppWeb.ApiSpec.spec()
schema = MyAppWeb.Schemas.UsersResponse.schema()
assert_schema(schema.example, "UsersResponse", api_spec)
end
```
## Validate Responses
API responses can be tested against schemas using `OpenApiSpex.TestAssertions` also:
```elixir
use MyAppWeb.ConnCase
import OpenApiSpex.TestAssertions
test "UserController produces a UsersResponse", %{conn: conn} do
api_spec = MyAppWeb.ApiSpec.spec()
json =
conn
|> get(user_path(conn, :index))
|> json_response(200)
assert_schema(json, "UsersResponse", api_spec)
end
```
## Experimental ExDoc-Based API Specifications
Starting with version 3.5.0, a new, experimental API is available to specify endpoints from the controller,
using ExDoc tags. See the example below.
Because this feature is experimental, it is likely to change in the future, until it becomes stable. Use
at your own risk.
```elixir
defmodule MyAppWeb.UserController do
use MyAppWeb, :controller
use OpenApiSpex.Controller
@doc """
List users
"""
@doc responses: %{
200 => {"Users", "application/json", MyAppWeb.Schema.Users}
}
def index(conn, _params) do
{:ok, users} = MyApp.Users.all()
json(conn, users)
end
@doc """
Update user
"""
@doc parameters: [
id: [in: :query, type: :string, required: true, description: "User ID"]
]
@doc request_body: {"Request body to update a User", "application/json", User, required: true}
@doc responses: %{
200 => {"User", "application/json", MyAppWeb.Schema.User}
}
def update(conn, %{id: id}) do
with {:ok, user} <- MyApp.Users.update(conn.body_params) do
json(conn, user)
end
end
end
```

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