OpenAPIDiff

This is a WIP diffing library for OpenAPI documentation. It produces a hierarchical list of changes between two versions of an API. Only OpenAPI v3.x is supported.

By default, it uses the Foundation JSONDecoder which battle-tested but notably slow on Linux. You can save a lot of time by passing the --fast flag or running diffs on YAML files if the Yams parser does an adequate job of parsing your OpenAPI document.

Example

To see an example of what this library produces when run against two YAML OpenAPI documents with the markdown option, take a look at the example folder.

Usage

Executable

The library ships with a very simple executable. If you just want to play with what you get out-of-the-box, the easiest option is to run the Docker image I host on Docker Hub.

The dockerized executable will require you to mount one or more volumes containing the versions of the API you wish to diff. Assuming you have the old and new versions of your API in the current working directory (named old.json and new.json), a simple invocation would be:

docker run --rm -v "$(pwd)/old.json:/api/old.json" -v "$(pwd)/new.json:/api/new.json" mattpolzin2/openapi-diff /api/old.json /api/new.json

You can pass mattpolzin2/openapi-diff the --markdown flag in addition to the two API document files to produce a markdown diff instead of the default plaintext diff.

You can pass mattpolzin2/openapi-diff the --fast flag to use faster (though less battle-tested) JSON parsing. The flag currently has no effect on YAML parsing.

For all options, see the --help.

Library

As a library, you first reference this package from your manifest or pull it in via Xcode.

...
dependencies: [
  .package(url: "https://github.com/mattpolzin/OpenAPIDiff.git", .upToNextMinor(from: "0.2.0")),
  ...
],
...

Then you can produce diffs with

import OpenAPIKit
import OpenAPIDiff

let file1 = try Data(contentsOf: oldOpenAPIFile)
let file2 = try Data(contentsOf: newOpenAPIFile)

let api1 = try JSONDecoder().decode(OpenAPI.Document.self, from: file1)
let api2 = try JSONDecoder().decode(OpenAPI.Document.self, from: file2)

let comparison = api1.compare(to: api2)

let markdownDiff = comparison.markdownDescription
let plaintextDiff = comparison.description

By default you will be getting entries for all of the things that have not changed as well as those that have changed. You can easily omit the similarities with

let differences = comparison.description { !$0.isSame }
let markdownDifferences = comparison.markdownDescription { !$0.isSame }

The structure you are producing is ApiDiff. You can take a look at ApiDiff.swift if you want to operate on the diff in some way different than the description() and markdownDescription() methods do.

Building From Source

The library target (OpenAPIDiff) and executable target (openapi-diff) can both be built quite easily with either swift build or by opening the repository root folder in Xcode 11.

The docker image can be build from the included Dockerfile with

docker build -t openapi-diff .