Beyond Documentation with OpenAPI

BEYOND DOCUMENTATION WITH OpenAPI

GET /SPEAKERS/BOYAN Boyan Yordanov @specter_bg PHP Varna and VarnaJS organizer VarnaLab member Developer@ShtrakBG

WHO LIKES WRITING DOCUMENTATION?

DOCUMENTATION THAT IS: “too long to read” “totally useless” “not updated”

JUST BORING

API SPECIFICATIONS machine readable easy to write more than documentation

I still have to write it, though. - me

I can do so many cool things with this de nition. - also me (a couple of months later)

WHY BOTHER WITH AN API SPECIFICATION?

HAVE YOU BEEN THIS PERSON? http://www.commitstrip.com

HOW ABOUT THIS?

OUR PROCESS HAS FAILED US

1. LITTLE UPFRONT DESIGN WORK

2. UNANNOUNCED OR MISCOMMUNICATED CHANGES

WASTED TIME AND A LOT OF FRUSTRATION

COMMON PROBLEMS changes aren’t properly tested clients constantly wait for the API documentation and code don’t match SDKs have another opinion

https://blog.apisyouwonthate.com/why-do-people-dislike-jsona7d67c8d38c1

WHAT CAN WE DO?

SPECIFICATION FIRST Nothing gets implemented until the API is de ned

SPECIFICATIONS AS CONTRACTS verify that the API does what it says

GAME PLAN 1. produce the API speci cation 2. generate docs and mock API 3. re ne the speci cation 4. use it in integration tests 5. work on the actual server code

POTENTIAL BENEFITS

1. THE SPEC IS THE SINGLE SOURCE OF TRUTH FOR OUR DESIGN

2. ALWAYS UP TO DATE DOCUMENTATION AND TESTS

3. WORK ON BACKEND AND CLIENTS INDEPENDENTLY

API SPECIFICATION FORMATS

API BLUEPRINT markdown based development is open on GitHub it’s quite mature there’s tooling for the most essential things mostly documentation oriented

RAML RESTful API Modeling Language yaml based syntax is quite similar to the OpenAPI Speci cation covers the whole design/development process

JSON SCHEMA not entirely fair to include it here json based focused only on the data model great for validation and tests includes syntax for describing hypermedia controls

don’t call it that please formerly known as Swagger yaml or json based very actively developed very active community

HOW TO WRITE AN OPENAPI SPECIFICATION read the spec at swagger.io/speci cation

BASIC STRUCTURE openapi: “3.0.0” info: # … servers: # … paths: # … tags: # … components: # …

LET’S BUILD A SIMPLE OPENAPI SPECIFICATION

BASIC INFORMATION ABOUT THE API info: description: >­ Imaginary API for managing meetups. Imagined for this PHPCE 2018 talk. version: ‘0.1’ title: Meetups Are Awesome API contact: email: boyan.yordanov.dev@gmail.com name: Boyan Yordanov url: ‘https://boyanyordanov.com’ license: # …

HOW CAN USERS ACCESS THE API servers: ­ url: ‘https://imaginary­meetups.com/api’ description: Imaginary API for managing Meetups ­ url: ‘https://staging.imaginary­meetups.com/api’ description: Staging server for the imaginary AP ­ url: ‘http://localhost:8080’ description: Development version of the API

it also supports templating servers: ­ url: https://{username}.api­server.com/api/ description: User specific URLs variables: username: default: demo description: assigned upon registration

WHAT CAN THE API DO

Just a list of paths and the possible requests and responses paths: /meetups # … /meetups/{id} # … /meetups/{id}/events # …

A path description /meetups: summary: meetups description: Meetups resource tags: # .. parameters: # .. get: # … post: # ..

DESCRIBING PARAMETERS /meetups: # … parameters: ­ name: city in: query / path / header description: Filter meetups based on city schema: type: string

handling array parameters /meetups: # … parameters: ­ name: technologies in: query description: Filter meetups based on city schema: type: array items: type: string style: form explode: false

Result ?technologies=php,apis,javascript

POSSIBLE RESPONSES /meetups/{id} get: responses: ‘200’: content: application/json: schema: # … ‘404’: content: application/problem+json: # …

SCHEMA OBJECTS “extended subset” of JSON Schema draft 5 support references in future will support current drafts of JSON Schema and other formats

example schema schema: type: object properties: id: type: string format: uuid name: type: string starting­date: type: string format: date

nullable elds city: description: either a string or null type: string nullable: true

other schema formats still a proposal schema: x­oas­draft­alternativeSchema: type: jsonSchema location: ./real­jsonschema.json https://github.com/OAI/OpenAPI-Speci cation/issues/1532

REFERENCE OBJECT object with $ref property reference objects in the same document reference external documents replace inline de nitions for most OpenAPI components

Replace almost anything in the spec schema: $ref: ‘#/components/schemas/Meetup’ # … responses: ‘200’: $ref: ‘MeetupsListResponse.yaml’

COMPONENTS components: schemas: # … responses: # … parameters: # … requestBodies: # … headers: # … examples: #

WE HAVE AN OPENAPI SPECIFICATION WHAT DO WE DO WITH IT?

EASY PICKINGS HTML DOCUMENTATION

Swagger UI - least favorite

Widdershins + Slate / Shins.js

REDOC

LINTER - SPECCY https://github.com/wework/speccy lints your speci cation supports rulesets docs preview with ReDoc resolve spec in one le supports external references written in json-schema

EDITORS everything supporting yaml

VSCode with openapi-lint extention validates and lints converts Swagger/OpenAPI 2.0 to OpenAPI 3.0 intellisense for both formats

Swagger Editor

Apicurio

OpenAPI GUI

SENYA EDITOR https://senya.io PhpStorm (JetBrains) plugin free for the time being smart completion live linting handles $refs well preview in Swagger UI ¯\ ( ) /¯ ツ

CODE GENERATION OPENAPI GENERATOR

community supported fork of swagger-codegen supports OpenAPI 3.0 Updated templates for different languages and frameworks

JANE-PHP/JANE-PHP https://github.com/janephp/janephp generates PSR-7 compatible SDKs can use different clients based on HTTPlug supports json-schema and OpenAPI OpenAPI v3 support was added recently

MOCK SERVERS APISprout SwaggerHub Stoplight.io

POSTMAN COLLECTIONS Apimatic.io upload/download or use API transform to and from OpenAPI lots of formats including Postman 2.0 Collections

OPENAPI / JSON SCHEMA CONVERSION https://github.com/mikunn/openapi2schema https://github.com/wework/json-schema-to-openapischema

WHY CONVERT? BEST OF BOTH WORLDS (sort of)

EXAMPLE TEST https://github.com/swaggest/php-json-schema /** @test */ public function it_tests_with_swaggest_json_schema() { $schema = $this­>loadSchema(‘events’); $response = $this­>get(‘/events’); $this­>assertValidResponse($schema, $response); }

EXAMPLE ASSERTION https://github.com/swaggest/php-json-schema protected function assertValidResponse( $schema, $response ){ $validator = Schema::import($schema); try { $data = json_decode($response­>getContent()); $validator­>in($data); $this­>assertTrue(true, ‘Something went wrong.’) } catch (InvalidValue $e) { $this­>fail($e­>getMessage()); } }

WORKING WITH THE SPECIFICATION https://github.com/apioo/psx-api Parse OpenAPI speci cation Generate from code Nice PHP API to work with the spec Supports other speci cations as well

PROOF OF CONCEPT TIME https://github.com/boyanyordanov/php-openapi-testing class ApiTest extends TestCase { use OpenAPITestTools\OpenAPIAssertions; /** @dataProvider getApiTestCases */ public function test_it_runs_openapi_based_tests( $path, $resource ) { $this­>assertValidContract($path, $resource); }

//… public function getApiTestCases(): array { $provider = new OpenAPITestTools\SpecDataProvide DIR . ‘/../../openapi.yaml’ ); return $provider­>getTestCases(); } }

MORE TOOLS OPENAPI.TOOLS thanks to Phil Sturgeon and Matthew Trask

THANK YOU! QUESTIONS? https://joind.in/talk/17ec9

RESOURCES Speci cation: https://swagger.io/speci cation https://github.com/OAI/OpenAPI-Speci cation - issues / PRs https://apisyouwonthate.com - books/blog/slack https://philsturgeon.uk https://apihandyman.io https://apievangelist.com http://json-schema.org http://www.commitstrip.com/en/2018/02/26/its-good-to-haveexperience/