[RK] Transform request & response fix, add documentation (#53)

Author: regan-karlewicz

README.md

@@ -331,6 +331,45 @@ api.mount('GetUser').withOptions({
 });
 ```
 
+### Request & Response Transformations
+
+GraphQL Rest Router allows the developer to add transformations on incoming requests or outgoing responses. By default, the regular axios transformers are used.
+
+Say the shape of data coming from GraphQL is not what your consuming application needs. Instead of putting transformational logic into your consuming components, you can encapsulate it into the REST layer.
+
+```js
+import GraphQLRestRouter from 'graphql-rest-router';
+
+const api = new GraphQLRestRouter('http://localhost:1227', schema);
+
+api.mount('GetImages').withOption('transformResponse', (response => {
+  const { data, errors } = response;
+
+  return {
+    data: {
+      // Turn images array into image URL map
+      images: data.images?.reduce((acc, img) => {
+        acc[img.url] = img;
+      }, {}),
+      errors,
+    }
+  };
+}));
+```
+
+You can also modify the outgoing request. These transforms should return a string request, but also allow you to modify the request headers.
+
+```js
+import GraphQLRestRouter from 'graphql-rest-router';
+
+const api = new GraphQLRestRouter('http://localhost:1227', schema);
+
+api.mount('GetImages').at('/images').withOption('transformRequest', (request, headers) => {
+  headers['X-My-Header'] = 'MyValue';
+  return request;
+});
+```
+
 ### Logging
 
 GraphQL Rest Router is capable of logging incoming requests and errors. When creating your router, you may use a logger of your own choice. GraphQL Rest Router allows you to configure log levels. The logger parameter must implement [ILogger](https://github.com/Econify/graphql-rest-router/blob/29cc328f23b8dd579a6f4af242266460e95e7d69/src/types.ts#L101-L107), and is compatible with most standard logging libraries.

example-consuming-client/package-lock.json

@@ -19,8 +19,7 @@ api.mount('GetCharacters').at('/characters/').withOptions({
 api.mount('GetCharacterById').at('/characters/:id');
 
 api.mount('GetLocations').at('/locations').withOption('transformResponse', (response) => {
-  const json = JSON.parse(response);
-  const { data, errors } = json;
+  const { data, errors } = response;
 
   return {
     data: {

example-consuming-client/src/api.ts

@@ -50,7 +50,7 @@
     "typescript": "4.0.3"
   },
   "dependencies": {
-    "axios": "^0.21.1",
+    "axios": "^0.21.4",
     "express": "^4.17.1",
     "graphql": "^14.0.2",
     "redis": "^3.1.2",

package-lock.json

@@ -3,7 +3,7 @@ import {
   OperationDefinitionNode, ListTypeNode, VariableDefinitionNode,
   parse, print, getOperationAST, NonNullTypeNode, DocumentNode,
 } from 'graphql';
-import { AxiosTransformer, AxiosInstance, AxiosRequestConfig } from 'axios';
+import axios, { AxiosTransformer, AxiosInstance, AxiosRequestConfig } from 'axios';
 import * as express from 'express';
 
 import { createHash } from 'crypto';
@@ -124,8 +124,8 @@ export default class Route implements IMountableItem {
   private schema!: DocumentNode;
   private logger!: Logger;
 
-  private transformRequestFn: AxiosTransformer[] = [];
-  private transformResponseFn: AxiosTransformer[] = [];
+  private transformRequestFn = axios.defaults.transformRequest as AxiosTransformer[];
+  private transformResponseFn = axios.defaults.transformResponse as AxiosTransformer[];
 
   private staticVariables: Record<string, unknown> = {};
   private defaultVariables: Record<string, unknown> = {};

package.json

@@ -56,10 +56,10 @@ describe('Route', () => {
           route = new Route({ schema, operationName: 'GetUserById', logger: console, logLevel: 3 });
         });
 
-        it('should allow you to change logging level with .setLogLevel()', () => {
+        it('should allow you to change logging level with .withOption()', () => {
           const newLogLevel = -1;
 
-          route.setLogLevel(newLogLevel);
+          route.withOption('logLevel', newLogLevel);
 
           assert.equal(route.logger.logLevel, newLogLevel);
         })
@@ -98,6 +98,65 @@ describe('Route', () => {
     });
   });
 
+  describe('#transformResponse', () => {
+    const operationName = 'GetUserById';
+    let route;
+
+    beforeEach(() => {
+      route = new Route({ schema, operationName });
+    });
+
+    it('should include the default axios transformResponse', () => {
+      assert.equal(route.transformResponseFn.length, 1)
+    });
+
+    it('should append additional transforms when called', () => {
+      route.withOption('transformResponse', (data) => 'testing transform')
+      assert.equal(route.transformResponseFn.length, 2);
+    });
+
+    it('should return data as JSON if response is stringified JSON', async () => {
+      const stringifiedJSON = "{\"data\":{\"users\":[{\"id\":1,\"name\":\"Charles Barkley\"}]}}";
+      const transformResponse = route.transformResponseFn[0];
+      const transitional = {
+        silentJSONParsing: true,
+        forcedJSONParsing: true,
+        clarifyTimeoutError: false
+      };
+      // HACK: transitional default not bound to axios function by default. This is fixed in
+      // later versions of axios (> 0.24.0), please remove after upgrade.
+      const data = await transformResponse.bind({ transitional })(stringifiedJSON);
+
+      assert.strictEqual(typeof data, 'object');
+    });
+  });
+
+  describe('#transformRequest', () => {
+    const operationName = 'GetUserById';
+    let route;
+
+    beforeEach(() => {
+      route = new Route({ schema, operationName });
+    });
+
+    it('should include the default axios transformRequest', () => {
+      assert.equal(route.transformRequestFn.length, 1)
+    });
+
+    it('should append additional transforms when called', () => {
+      route.withOption('transformRequest', (data) => 'testing transform')
+      assert.equal(route.transformRequestFn.length, 2);
+    });
+
+    it('should return request', async () => {
+      const stringifiedRequest = `{"query":"{users}","operationName":"${operationName}"}`;
+      const transformRequest = route.transformRequestFn[0];
+      const data = await transformRequest(stringifiedRequest);
+
+      assert.strictEqual(data, stringifiedRequest);
+    });
+  });
+
   describe('private#setOperationName', () => {
     it('throws an error if operation name does not exist in the schema', () => {
       assert.throws(() => {
@@ -141,7 +200,6 @@ describe('Route', () => {
       const operationAsPath = `/${operationName}`;
 
       const route = new Route({ schema, operationName });
-      
       assert.equal(route.operationName, operationName);
       assert.equal(route.path, operationAsPath);
     });