Ensure constrained routes are matched before unconstrained routes reg…

…ardless of insertion order

README.md

@@ -114,6 +114,7 @@ findMyWay.on('GET', '/', { constraints: { host: 'example.com' } }, (req, res) =>
 
 Constraints can be combined, and route handlers will only match if __all__ of the constraints for the handler match the request. `find-my-way` does a boolean AND with each route constraint, not an OR.
 
+`find-my-way` will try to match the most constrained handlers first before handler with fewer or no constraints.
 
 <a name="custom-constraint-strategies"></a>
 ### Custom Constraint Strategies
@@ -306,6 +307,8 @@ and the URL of the incoming request is /33/foo/bar,
 the second route will be matched because the first chunk (33) matches the static chunk.
 If the URL would have been /32/foo/bar, the first route would have been matched.
 
+Once a url has been matched, `find-my-way` will figure out which handler registered for that path matches the request if there are any constraints. `find-my-way` will check the most constrained handlers first, which means the handlers with the most keys in the `constraints` object.
+
 <a name="supported-methods"></a>
 ##### Supported methods
 The router is able to route all HTTP methods defined by [`http` core module](https://nodejs.org/api/http.html#http_http_methods).

node.js

@@ -175,6 +175,8 @@ Node.prototype.addHandler = function (handler, params, store, constraints) {
   }
 
   this.handlers.push(handlerObject)
+  // Sort the most constrained handlers to the front of the list of handlers so they are tested first.
+  this.handlers.sort((a, b) => Object.keys(a.constraints).length - Object.keys(b.constraints).length)
 
   if (Object.keys(constraints).length > 0) {
     this.hasConstraints = true

test/constraint.host.test.js

@@ -36,22 +36,6 @@ test('A route supports wildcard host constraints', t => {
   t.notOk(findMyWay.find('GET', '/', { host: 'example.com' }))
 })
 
-test('A route could support multiple host constraints while versioned', t => {
-  t.plan(6)
-
-  const findMyWay = FindMyWay()
-
-  findMyWay.on('GET', '/', { constraints: { host: 'fastify.io', version: '1.1.0' } }, beta)
-  findMyWay.on('GET', '/', { constraints: { host: 'fastify.io', version: '2.1.0' } }, gamma)
-
-  t.strictEqual(findMyWay.find('GET', '/', { host: 'fastify.io', version: '1.x' }).handler, beta)
-  t.strictEqual(findMyWay.find('GET', '/', { host: 'fastify.io', version: '1.1.x' }).handler, beta)
-  t.strictEqual(findMyWay.find('GET', '/', { host: 'fastify.io', version: '2.x' }).handler, gamma)
-  t.strictEqual(findMyWay.find('GET', '/', { host: 'fastify.io', version: '2.1.x' }).handler, gamma)
-  t.notOk(findMyWay.find('GET', '/', { host: 'fastify.io', version: '3.x' }))
-  t.notOk(findMyWay.find('GET', '/', { host: 'something-else.io', version: '1.x' }))
-})
-
 test('A route supports multiple host constraints (lookup)', t => {
   t.plan(4)
 

test/constraints.test.js

@@ -0,0 +1,90 @@
+'use strict'
+
+const t = require('tap')
+const test = t.test
+const FindMyWay = require('..')
+const alpha = () => { }
+const beta = () => { }
+const gamma = () => { }
+
+test('A route could support multiple host constraints while versioned', t => {
+  t.plan(6)
+
+  const findMyWay = FindMyWay()
+
+  findMyWay.on('GET', '/', { constraints: { host: 'fastify.io', version: '1.1.0' } }, beta)
+  findMyWay.on('GET', '/', { constraints: { host: 'fastify.io', version: '2.1.0' } }, gamma)
+
+  t.strictEqual(findMyWay.find('GET', '/', { host: 'fastify.io', version: '1.x' }).handler, beta)
+  t.strictEqual(findMyWay.find('GET', '/', { host: 'fastify.io', version: '1.1.x' }).handler, beta)
+  t.strictEqual(findMyWay.find('GET', '/', { host: 'fastify.io', version: '2.x' }).handler, gamma)
+  t.strictEqual(findMyWay.find('GET', '/', { host: 'fastify.io', version: '2.1.x' }).handler, gamma)
+  t.notOk(findMyWay.find('GET', '/', { host: 'fastify.io', version: '3.x' }))
+  t.notOk(findMyWay.find('GET', '/', { host: 'something-else.io', version: '1.x' }))
+})
+
+test('Constrained routes are matched before unconstrainted routes when the constrained route is added last', t => {
+  t.plan(3)
+
+  const findMyWay = FindMyWay()
+
+  findMyWay.on('GET', '/', {}, alpha)
+  findMyWay.on('GET', '/', { constraints: { host: 'fastify.io' } }, beta)
+
+  t.strictEqual(findMyWay.find('GET', '/', {}).handler, alpha)
+  t.strictEqual(findMyWay.find('GET', '/', { host: 'fastify.io' }).handler, beta)
+  t.strictEqual(findMyWay.find('GET', '/', { host: 'example.com' }).handler, alpha)
+})
+
+test('Constrained routes are matched before unconstrainted routes when the constrained route is added first', t => {
+  t.plan(3)
+
+  const findMyWay = FindMyWay()
+
+  findMyWay.on('GET', '/', { constraints: { host: 'fastify.io' } }, beta)
+  findMyWay.on('GET', '/', {}, alpha)
+
+  t.strictEqual(findMyWay.find('GET', '/', {}).handler, alpha)
+  t.strictEqual(findMyWay.find('GET', '/', { host: 'fastify.io' }).handler, beta)
+  t.strictEqual(findMyWay.find('GET', '/', { host: 'example.com' }).handler, alpha)
+})
+
+test('Routes with multiple constraints are matched before routes with one constraint when the doubly-constrained route is added last', t => {
+  t.plan(3)
+
+  const findMyWay = FindMyWay()
+
+  findMyWay.on('GET', '/', { constraints: { host: 'fastify.io' } }, alpha)
+  findMyWay.on('GET', '/', { constraints: { host: 'fastify.io', version: '1.0.0' } }, beta)
+
+  t.strictEqual(findMyWay.find('GET', '/', { host: 'fastify.io' }).handler, alpha)
+  t.strictEqual(findMyWay.find('GET', '/', { host: 'fastify.io', version: '1.0.0' }).handler, beta)
+  t.strictEqual(findMyWay.find('GET', '/', { host: 'fastify.io', version: '2.0.0' }).handler, alpha)
+})
+
+test('Routes with multiple constraints are matched before routes with one constraint when the doubly-constrained route is added first', t => {
+  t.plan(3)
+
+  const findMyWay = FindMyWay()
+
+  findMyWay.on('GET', '/', { constraints: { host: 'fastify.io', version: '1.0.0' } }, beta)
+  findMyWay.on('GET', '/', { constraints: { host: 'fastify.io' } }, alpha)
+
+  t.strictEqual(findMyWay.find('GET', '/', { host: 'fastify.io' }).handler, alpha)
+  t.strictEqual(findMyWay.find('GET', '/', { host: 'fastify.io', version: '1.0.0' }).handler, beta)
+  t.strictEqual(findMyWay.find('GET', '/', { host: 'fastify.io', version: '2.0.0' }).handler, alpha)
+})
+
+test('Routes with multiple constraints are matched before routes with one constraint before unconstrained routes', t => {
+  t.plan(3)
+
+  const findMyWay = FindMyWay()
+
+  findMyWay.on('GET', '/', { constraints: { host: 'fastify.io', version: '1.0.0' } }, beta)
+  findMyWay.on('GET', '/', { constraints: { host: 'fastify.io' } }, alpha)
+  findMyWay.on('GET', '/', { constraints: {} }, gamma)
+
+  t.strictEqual(findMyWay.find('GET', '/', { host: 'fastify.io', version: '1.0.0' }).handler, beta)
+  t.strictEqual(findMyWay.find('GET', '/', { host: 'fastify.io', version: '2.0.0' }).handler, alpha)
+  t.strictEqual(findMyWay.find('GET', '/', { host: 'example.io' }).handler, gamma)
+})