zswag 0.7.0rc0

Server middleware for implementing zserio services at warp 10.

Zswag

Convenience functionality to create python modules from zserio services at warp speed. Translate/verify Zserio services to/with OpenAPI/Swagger and serve them in Flask/Connexion WSGI apps.

Installation

Just run

pip3 install zswag

Alternatively, clone this repository, and run

pip3 install -e .

Running the remote calculator test example

PYTHONPATH=$PWD/test
python3 -m calc server &
python3 -m calc client

Creating a Swagger service from zserio

ZserioSwaggerApp gives you the power to marry a user-written app controller with a zserio-generated app server class (argument parser/response serialiser) and a fitting Swagger OpenAPI spec.

Example

import zswag
import zserio
import my.app.controller

zserio.generate("myapp/service.zs", "myapp")
from myapp.service import Service

# The OpenApi argument `yaml_path=...` is optional
app = zswag.ZserioSwaggerApp(my.app.controller, Service)

Here, the API endpoints are routed to my/app/controller.py, which might look as follows:

# Written by you
def myApi(request):
    return "response"

# Injected by ZserioSwaggerApp
# _service = Service()
# _service.myApi = lambda request: _service._myApiMethod(request)
# _service._myApiImpl = my.app.controller.myApi

Using the client

If you have a service called my.package.Service, then zserio will automatically generate a client for the service under my.package.Service.Client. This client can be instantiated alas ...

from my.package import Service
from pyzswagcl import HttpClient
client = Service.Client(HttpClient(spec=f"http://localhost:5000/openapi.json"))

zswag.HttpClient provides the service client interface expected by zserio. It reads HTTP specifics for the service from an OpenAPI YAML or JSON spec that must be located under the given path or URL. For more options with the HttpClient constructor check out it's doc-string.

Swagger UI

If you have installed pip install connexion[swagger-ui], you can view API docs of your service under [/prefix]/ui.

OpenAPI YAML spec

YAML file location/auto-generation

• If you specify a non-empty path to a file which does not yet exist, the OpenAPI spec is auto-generated in that location.
• If you specify an empty YAML path, the yaml file is placed next to the <service>.zs source-file.
• If you specify an existing file, zswag will simply verify all the methods specified in your zserio service are also reflected in the OpenAPI-spec.

OpenAPI Spec Options

Options Overview

ZserioSwaggerApp and zswag_client.HttpClient currently offer several degrees of freedom regarding HTTP-specifics in the OpenAPI YAML file:

• HTTP Method
• Parameter Format
• Server URL Base Path

Option 🌟1: HTTP method

To change the HTTP method, simply place the desired method as the key under the method path, such as in the following example:

paths:
  /methodName:
    {get|post|put|patch|delete}:
      ...

Option 🌟2: Zserio request blob in body

requestBody:
  content:
    application/x-zserio-object:
      schema:
        type: string

Option 🌟3: Zserio request blob in URL parameter

parameters:
- description: ''
  in: query|path
  name: parameterName
  required: true
  x-zserio-request-part: "*"
  schema:
    format: string|byte|base64|base64url|hex|binary

About the format specifier value:

• Both string and binary result in a raw URL-encoded string.
• Both byte and base64 result in a standard Base64-encoded value. The base64url option indicates URL-safe Base64 format.
• The hex encoding produces a hexadecimal encoding of the request blob.

Option 🌟4: Zserio request part, single value

parameters:
- description: ''
  in: query|path
  name: parameterName
  required: true
  x-zserio-request-part: "field[.subfield]*"
  schema:
    format: string|byte|base64|base64url|hex|binary

In this case, x-zserio-request-part should point to an atomic built-in type, such as uint8, float32, extern etc. Note that uint8[] array fields receive special treatment: They are transferred as single-value blobs, not as arrays.

The format value effect remains as explained above. A small difference exists for integer types: Their hexadecimal representation will be the natural numeric one, not the binary.

Option 🌟5: Zserio request part, array

parameters:
- description: ''
  in: query|path
  style: form|simple|label|matrix
  explode: true|false
  name: parameterName
  required: true
  x-zserio-request-part: "field[.subfield]*"
  schema:
    format: string|byte|base64|base64url|hex|binary

In this case, x-zserio-request-part should point to an array of atomic built-in types. The array will be encoded according to the format, style and explode specifiers.

Option 🌟6: Zserio request part, dictionary

In this case, x-zserio-request-part should point to a zserio struct. The OpenAPI schema options are the same as for arrays. All fields of the designated struct which have an atomic built-in type are exposed as key-value pairs. The key-value-pairs will be encoded according to the format, style and explode specifiers.

Option 🌟7: Server URL Base Path

OpenAPI allows for a servers field in the spec that lists URL path prefixes under which the specified API may be reached. A zswag_client.HttpClient instance looks into this list and determines the URL base path it uses from the first entry in this list. A sample entry might look as follows:

servers:
- http://unused-host-information/path/to/my/api

The zswag_client.HttpClient will then call methods with your specified host and port, but prefix the /path/to/my/api string.

Documentation extraction

When the OpenAPI/Swagger YAML is auto-generated, ZserioSwaggerApp tries to populate the service/method/argument/result descriptions with doc-strings which are extracted from the zserio sources.

For structs and services, the documentation is expected to be enclosed by /*! .... !*/ markers preceding the declaration:

/*!
### My Markdown Struct Doc
I choose to __highlight__ this word.
!*/

struct MyStruct {
    ...
}

For service methods, a single-line doc-string is parsed which immediately precedes the declaration:

/** This method is documented. */
ReturnType myMethod(ArgumentType);