Dennis O'Keeffe
Posted on September 20, 2020
This is the next post in a short series of spikes I am doing to better understand JSON Schema and OpenAPI v3.
In the previous two posts, we looked at validating and converting JSON schema to TypeScript, then validating the OpenAPI schema itself. In this post, we are going to go one step further and test for breaking changes.
# in a project directory with yarn setup
yarn add openapi-diff
# preparing the files
touch books.json openapi.json
Setting up the required files
We are going to continue on with the values that we had from the previous posts which will model a book and expect /books to have a 200 response that returns an array of books.
For books.json:
{
"$schema": "http://json-schema.org/draft-07/schema#",
"id": "#/components/schemas/Book",
"definitions": {
"user": {
"type": "object",
"properties": {
"name": { "type": "string" },
"preferredName": { "type": "string" },
"age": { "type": "number" },
"gender": { "enum": ["male", "female", "other"] }
},
"required": ["name", "preferredName", "age", "gender"]
}
},
"type": "object",
"properties": {
"author": { "$ref": "#/components/schemas/User" },
"title": { "type": "string" },
"publisher": { "type": "string" }
},
"required": ["author", "title", "publisher"]
}
For openapi.json:
{
"openapi": "3.0.3",
"info": {
"title": "Sample API",
"description": "Optional multiline or single-line description in [CommonMark](http://commonmark.org/help/) or HTML.",
"version": "0.1.0"
},
"paths": {
"/books": {
"get": {
"summary": "Get all books",
"responses": {
"200": {
"description": "A list of books",
"content": {
"application/json": {
"schema": {
"type": "array",
"items": {
"$ref": "#/components/schemas/Book"
}
}
}
}
}
}
}
}
}
}
Running the validation
const openApiDiff = require("openapi-diff")
const util = require("util")
const fs = require("fs")
const path = require("path")
const main = async () => {
// read the schema details
const schemaFilepath = path.join(__dirname, "book.json")
const bookSchema = JSON.parse(fs.readFileSync(schemaFilepath, "utf-8"))
// Validating the OpenAPI
const openApiJsonFilepath = path.join(__dirname, "openapi.json")
const openApiSchema = JSON.parse(
fs.readFileSync(openApiJsonFilepath, "utf-8")
)
// define a copy that we will make breaking changes to
const openApiSchemaNew = Object.assign({}, openApiSchema)
// add in the component
openApiSchema.components = {
schemas: {
User: bookSchema.definitions.user,
Book: {
type: bookSchema.type,
properties: bookSchema.properties,
required: bookSchema.required,
},
},
}
// mimic the above behaviour
openApiSchemaNew.components = {
schemas: {
User: bookSchema.definitions.user,
Book: {
type: bookSchema.type,
properties: {
title: { type: "string" },
},
required: bookSchema.required,
},
},
}
// openApiDiff
const result = await openApiDiff.diffSpecs({
sourceSpec: {
content: JSON.stringify(openApiSchema),
location: "old",
format: "openapi3",
},
destinationSpec: {
content: JSON.stringify(openApiSchemaNew),
location: "new",
format: "openapi3",
},
})
if (result.breakingDifferencesFound) {
console.log("Breaking change found!")
console.log(util.inspect(result, { depth: null }))
}
}
main()
In the above script, we are adding a breaking change by removing two of the expected properties.
If we run node index.js, our breaking change will show!
Breaking change found!
{
breakingDifferences: [
{
type: 'breaking',
action: 'add',
code: 'response.body.scope.add',
destinationSpecEntityDetails: [
{
location: 'paths./books.get.responses.200.content.application/json.schema',
value: {
type: 'array',
items: {
type: 'object',
properties: { title: { type: 'string' } },
required: [ 'author', 'title', 'publisher' ]
}
}
}
],
entity: 'response.body.scope',
source: 'json-schema-diff',
sourceSpecEntityDetails: [
{
location: 'paths./books.get.responses.200.content.application/json.schema',
value: {
type: 'array',
items: {
type: 'object',
properties: {
author: {
type: 'object',
properties: {
name: { type: 'string' },
preferredName: { type: 'string' },
age: { type: 'number' },
gender: { enum: [ 'male', 'female', 'other' ] }
},
required: [ 'name', 'preferredName', 'age', 'gender' ]
},
title: { type: 'string' },
publisher: { type: 'string' }
},
required: [ 'author', 'title', 'publisher' ]
}
}
}
],
details: {
differenceSchema: {
type: 'array',
items: {
type: 'object',
properties: { title: { type: 'string' } },
required: [ 'author', 'title', 'publisher' ]
},
not: {
type: 'array',
items: {
type: 'object',
properties: {
author: {
type: 'object',
properties: {
name: { type: 'string' },
preferredName: { type: 'string' },
age: { type: 'number' },
gender: true
},
required: [ 'name', 'preferredName', 'age', 'gender' ]
},
publisher: { type: 'string' },
title: { type: 'string' }
},
required: [ 'author', 'publisher', 'title' ]
}
}
}
}
}
],
breakingDifferencesFound: true,
nonBreakingDifferences: [],
unclassifiedDifferences: []
}
Amazing! Since we are exiting with a non-zero code, we can start pulling things like this short script into our CI tools.
Resources And Further Reading
Image credit: Laura Chouette
Originally posted on my blog. Follow me on Twitter for more hidden gems @dennisokeeffe92.
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Dennis O'Keeffe
Posted on September 20, 2020
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