fix: add check for existing clients

Author: rohit-gohri

src/index.js

@@ -242,6 +242,8 @@ module.exports.addTargetClient = function (target, client) {
     throw new Error('The supplied custom target client must contain an `info` object.')
   } else if (!('key' in client.info) || !('title' in client.info)) {
     throw new Error('The supplied custom target client must have an `info` object with a `key` and `title` property.')
+  } else if (targets[target].hasOwnProperty(client.info.key)) {
+    throw new Error('The supplied custom target client already exists, please use a different key')
   }
 
   targets[target][client.info.key] = client

test/targets.js

@@ -143,14 +143,20 @@ describe('Custom targets', function () {
       customClient = {
         ...targets.node.request,
         info: {
-          key: 'axios',
+          key: 'axios-test',
           title: 'Axios',
           link: 'https://www.npmjs.com/package/axios',
           description: 'Promise based HTTP client for the browser and node.js'
         }
       }
     })
 
+    it('should throw if client already exists', function () {
+      (function () {
+        HTTPSnippet.addTargetClient('node', {...customClient, info: {...customClient.info, key: 'axios'}})
+      }).should.throw(Error)
+    })
+
     it("should throw if the client's target does not exist", function () {
       (function () {
         HTTPSnippet.addTargetClient('node.js', customClient)