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

The online version of the converter/validator runs on a Linode VPS. If you are considering a hosted server, please sign up through this link so we both receive free credit.

Currently tracking v3.0.x

Installation:

This is a node.js module, which you can run on the command line. First ensure you have npm installed (tested on version 6.1+), and then install as follows:

$ npm install -g swagger2openapi

Or, add it to your node.js projects as shown below in option B.

Usage:

A. Command line:

swagger2openapi [options] [filename|url]
Options:
  --refSiblings        mode to handle $ref's with sibling properties
                                        [choices: "remove", "preserve", "allOf"]
  --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"]
  -f, --fatal          make resolution errors fatal                    [boolean]
  -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]
  -t, --targetVersion  override default target version of 3.0.0         [string]
  -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           write YAML, default JSON (overridden by --outfile
                       filepath extension)                             [boolean]
  -b, --rbname         Extension to use to preserve body parameter names in
                       converted operations ("" == disabled)
                                                          [string] [default: ""]

B. Node.js API:

const converter = require('swagger2openapi');
let 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

See the boast command-line tool for a fuller example of converting, validating and linting.

See here for complete documentation of the options object.

C. Browser:

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

Browser Support

See initial documentation.

Features

OpenAPI 3.0.x validation

oas-validate can be used as a 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 validator 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.

oas-validate.js [options] {path-to-docs}...

Options:
  --lint            lint the definition                                [boolean]
  --validateSchema  Run schema validation step: first, last* or never   [string]
  --warnOnly        Do not throw on non-patchable errors               [boolean]
  -h, --help        Show help                                          [boolean]
  --version         Show version number                                [boolean]
  -e, --encoding    encoding for input/output files   [string] [default: "utf8"]
  -f, --fail        path to docs expected to fail                       [string]
  -j, --jsonschema  path to alternative JSON schema                     [string]
  -l, --laxurls     lax checking of empty urls                         [boolean]
  -m, --mediatype   check media-types against RFC pattern              [boolean]
  -n, --nopatch     do not patch minor errors in the source definition [boolean]
  -o, --output      output conversion result  [string] [default: "openapi.yaml"]
  -q, --quiet       do not show test passes on console, for CI         [boolean]
  -r, --resolve     resolve external references                        [boolean]
  -s, --stop        stop on first error                                [boolean]
  -v, --verbose     increase verbosity                                   [count]
  -w, --whatwg      enable WHATWG URL parsing                          [boolean]
  -y, --yaml        skip YAML-safe test                                [boolean]

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 oas-validate [-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 8.x and 10.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 74,426 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.