swagger2openapi

What is swagger2openapi?

The swagger2openapi npm package is designed to convert Swagger 2.0 definitions into OpenAPI 3.0.x, facilitating the transition to the newer OpenAPI specification. It supports both command-line and programmatic usage, making it a versatile tool for developers working with API documentation and specifications.

What are swagger2openapi's main functionalities?

Conversion of Swagger 2.0 to OpenAPI 3.0

This feature allows users to programmatically convert Swagger 2.0 API definitions to OpenAPI 3.0 specifications. The code sample demonstrates how to load a Swagger 2.0 JSON file, convert it, and then log the resulting OpenAPI 3.0 specification.

const converter = require('swagger2openapi');
const swagger = require('./swagger.json');

converter.convertObj(swagger, {}, (err, options) => {
  if (err) {
    console.error(err);
  } else {
    console.log(options.openapi);
  }
});

Validation of converted OpenAPI 3.0 definitions

Beyond conversion, the package also offers validation of the resulting OpenAPI 3.0 definitions. This ensures that the conversion process not only translates the specification but also checks for any inconsistencies or errors in the new format.

const converter = require('swagger2openapi');
const swagger = require('./swagger.json');

converter.convertObj(swagger, {validate: true}, (err, options) => {
  if (err) {
    console.error('Validation error:', err);
  } else {
    console.log('Validation successful. OpenAPI 3.0 output:', options.openapi);
  }
});

Command-line conversion

For users preferring command-line tools, swagger2openapi provides a straightforward way to convert Swagger 2.0 files to OpenAPI 3.0 by specifying the input and output files directly in the terminal.

swagger2openapi swagger.json -o openapi.json

Other packages similar to swagger2openapi

swagger-parser

Swagger Parser is a package that can validate and dereference Swagger files. While it primarily focuses on Swagger 2.0, it also supports OpenAPI 3.0 to some extent. Compared to swagger2openapi, Swagger Parser offers validation and dereferencing but not direct conversion between the two specifications.

openapi3-ts

openapi3-ts provides TypeScript definitions for OpenAPI 3.0. While it doesn't offer conversion capabilities, it's a useful tool for developers working with OpenAPI 3.0 in TypeScript projects, complementing swagger2openapi by providing type checking and autocompletion.

README

swagger2openapi

Convert Swagger 2.0 definitions into OpenApi 3.0.x

Currently tracking v3.0.0

If you are using Node.js 4 - please use the --harmony flag

Usage:

swagger2openapi [options] [filename|url]
Options:
  --warnProperty    Property name to use for warning extensions
                                             [string] [default: "x-s2o-warning"]
  --version         Show version number                                [boolean]
  -c, --components  output information to unresolve a definition       [boolean]
  -d, --debug       enable debug mode, adds specification-extensions   [boolean]
  -e, --encoding    encoding for input/output files   [string] [default: "utf8"]
  -h, --help        Show help                                          [boolean]
  -i, --indent      JSON indent to use, defaults to 4 spaces            [string]
  -o, --outfile     the output file to write to                         [string]
  -p, --patch       fix up small errors in the source definition       [boolean]
  -r, --resolve     resolve external references                        [boolean]
  -u, --url         url of original spec, creates x-origin entry        [string]
  -v, --verbose     increase verbosity                                   [count]
  -w, --warnOnly    Do not throw on non-patchable errors, add warning extensions
                                                                       [boolean]
  -y, --yaml        read and write YAML, default JSON                  [boolean]

or use the APIs:

var converter = require('swagger2openapi');
var options = {};
//options.patch = true; // fix up small errors in the source definition
//options.warnOnly = true; // Do not throw on non-patchable errors
converter.convertObj(swagger, options, function(err, options){
  // options.openapi contains the converted definition
});
// also available are asynchronous convertFile, convertUrl, convertStr and convertStream functions
// if you omit the callback parameter, you will instead receive a Promise

var validator = require('swagger2openapi/validate.js');
var options = {};
validator.validate(openapi, options, function(err, options){
  // options.valid contains the result of the validation
  // options.context now contains a stack (array) of JSON-Pointer strings
});
// also available is a synchronous validateSync method which returns a boolean

See here for complete documentation of the options object.

Or use the online version which also includes its own API.

Browser Support

See initial documentation.

Features

OpenAPI 3.0.x validation

The testRunner harness can also be used as a simple validator if given one or more existing OpenAPI 3.x definitions. The validator (however it is called) uses WHATWG URL parsing if available (node 7.x and above). The testRunner can have a linting mode enabled with the --lint option. Rules are defined here. Contributions of rules and rule actions for the linter are very much appreciated.

Reference preservation

swagger2openapi preserves almost all $ref JSON references in your API definition, and does not dereference every item, as with some model-based parsers. The exception is internal references within externally referenced documents.

Schema transformations

Swagger2openapi will automatically 'repair' a number of problems where non-compliant Swagger 2.0 schemas have been used. It will attempt to transform JSON schemas (used incorrectly) into OpenAPI 3.0.x Schema objects.

Specification extensions

swagger2openapi has support for a limited number of real-world specification extensions which have a direct bearing on the conversion. All other specification extensions are left untouched. swagger2openapi is swaggerplusplus-compatible.

It is expected to be able to configure the process of specification-extension modification using options or a plugin mechanism in a future release.

Tests

To run a test-suite:

node testRunner [-f {path-to-expected-failures}]... [{path-to-APIs|single-file...}]

The test harness currently expects files with a .json or .yaml extension, or a single named file, and has been tested on Node.js versions 4.x, 6.x and 8.x LTS (it is not recommended to run the test suite under Node.js versions >=7.0.0 and <8.7.0 because of this bug) against

• APIs.guru
• Mermade OpenApi specifications collection
• OpenAPI3-Examples (pass/fail)
• SOM-Research collection

Additionally swagger2openapi has been tested on a corpus of 34,679 real-world valid Swagger 2.0 definitions from GitHub and SwaggerHub. However, if you have a definition which causes errors in the converter or does not pass validation, please do not hesitate to raise an issue.

Regression tests

Regression tests (thanks @domharrington) live in the /test directory and can be run with npx mocha. Each sub-directory should contain an input swagger.yaml file, an expected output openapi.yaml file and an optional options.yaml file. You can put private test cases in sub-directories starting with an underscore character.

License

BSD-3-Clause except the openapi-3.0.json schema, which is taken from the OpenAPI-Specification and the alternative gnostic-3.0.json schema, which is originally from Google Gnostic. Both of these are licensed under the Apache-2 license.