koa-semver

Match middleware with Semantic Versioning.

Built with npm/node-semver to match familiar npm style dependency syntax and usage, but for middleware and routes.

Requisites:

• Node.js >= 7.6.0
• Koa >= 2.0.0

Installation

npm install --save koa-semver
 
# with yarn: 
yarn add koa-semver

Usage

koa-semver allows multiple usage options, but it is strongly recommended to use with koa-router.

Basic Versioning

A sample Koa server would be:

"use strict";
 
const Koa = require("koa");
const Router = require("koa-router");
const Semver = require("koa-semver");
 
const app = new Koa();
const router = new Router();
 
// Add handlers by priority
// (Descending order)
const ver = new Semver([
  Semver.handlers.header("X-Semver"),
  Semver.handlers.param(":version"),
  Semver.handlers.query("version"),
]);
 
// Newer middleware or routes should be placed on top
// (Descending order)
router.get("/:version/users", ver.match("~2.10.0", ctx => {
  ctx.body = { // Latest
    users: {
      administrators: [],
      clients: [],
    },
  };
}));
 
router.get("/:version/users", ver.match("^1.2.0", ctx => {
  ctx.body = { // Legacy
    users: []
  };
}));
 
app.use(router.routes());
 
app.listen(3000);

Client side usage:

# Latest version 
$ curl http://localhost:3000/_/users
$ curl -H "X-Semver: 2.10.1" http://localhost:3000/_/users
{
    "users": {
        "administrators": [],
        "clients": []
    }
}
 
# Latest version (headers has more priority than route param) 
$ curl -H "X-Semver: 2.10.1" http://localhost:3000/1.2.5/users
{
    "users": {
        "administrators": [],
        "clients": []
    }
}

# Specific version 
$ curl http://localhost:3000/1.3.0/users
$ curl http://localhost:3000/_/users?version=1.4.0
{
    "users": []
}

# Unknown version 
$ curl http://localhost:3000/3.0.0/users
$ curl http://localhost:3000/0.1.0/users
Not Found

Semver state variable

It is possible to know about the requested and matching versions:

router.get("/:version/users", ver.match("^1.2.0", ctx => {
  ctx.body = ctx.state.semver;
}));

Create a matcher

Sometimes we want to reuse the matching version, so we can:

const ver = new Semver();
ver.use(Semver.handlers.header("X-Semver"));
 
const matcher = ver.matcher("^1.0.0");
 
const router = new Router();
router.get("/users", matcher(async ctx => {
  // ...
}));
router.post("/users/:id/comments", matcher(async ctx => {
  // ...
}));

Another way is:

const app = new Koa();
 
const ver = new Semver();
ver.use(Semver.handlers.header("X-Semver"));
 
const router = new Router();
router.get("/users", async ctx => {
  // ...
});
router.post("/users/:id/comments", async ctx => {
  // ...
});
 
app.use(ver.match("^1.0.0", router.routes()));

Multiple matching

It is responsibility of the developer to stop the middleware propagation. So it is possible to match multiples routes or add conditional middleware using koa-semver;

const app = new Koa();
const router = new Router();
const ver = new Semver();
ver.use(Semver.handlers.header("X-Semver"));
 
app.use(ver.match("1.x || >=2.5.0 || 5.0.0 - 7.2.3", (ctx, next) => {
  // Patch some buggy versions
  ctx.state.something = true;
  ctx.body = [];
  return next(); // <- Continue middleware chain
}));
 
router.get("/endpoint", ver.match("^1.2.0", async (ctx, next) => {
  ctx.body.append("Hello!");
  await next(); // <- Continue middleware chain
}));
 
router.get("/endpoint", ver.match("^1.1.0", async ctx => {
  ctx.body.append("World!");
  // We broke the chain
}));
 
router.get("/endpoint", ver.match("^1.0.1", async ctx => {
  // This would never match
}));
 
// ...
 
app.use(router.routes());

In this case a GET request to /endpoint with X-Semver: 1.2.0 will match the first two routes and will return:

["Hello!", "World!"]

Testing

Run Jest test suite with:

yarn test
 
# With coverage 
yarn test -- --coverage
 
# Watch for changes 
yarn test -- --watch