Added a way to invoke external functions. (#42)

* Added a way to invoke external functions.

* Added specification of a method for an external functon. Added an example for usage of external functions

* Moved function configuration into plugin config.

* Updated readme docs for external invoke functions. Added validateStatus false for external lambda handler.

Author: egordm

README.md

@@ -56,6 +56,7 @@ Put options under `custom.appsync-simulator` in your `serverless.yml` file
 | refMap                   | {}                    | A mapping of [resource resolutions](#resource-cloudformation-functions-resolution) for the `Ref` function                                                           |
 | getAttMap                | {}                    | A mapping of [resource resolutions](#resource-cloudformation-functions-resolution) for the `GetAtt` function                                                        |
 | importValueMap           | {}                    | A mapping of [resource resolutions](#resource-cloudformation-functions-resolution) for the `ImportValue` function                                                   |
+| functions                | {}                    | A mapping of [external functions](#functions) for providing invoke url for external fucntions                                                                                |
 | dynamoDb.endpoint        | http://localhost:8000 | Dynamodb endpoint. Specify it if you're not using serverless-dynamodb-local. Otherwise, port is taken from dynamodb-local conf                                      |
 | dynamoDb.region          | localhost             | Dynamodb region. Specify it if you're connecting to a remote Dynamodb intance.                                                                                      |
 | dynamoDb.accessKeyId     | DEFAULT_ACCESS_KEY    | AWS Access Key ID to access DynamoDB                                                                                                                                |
@@ -202,6 +203,20 @@ For now, the supported resources to be automatically resovled by `Ref:` are:
 
 Feel free to open a PR or an issue to extend them as well.
 
+# External functions
+When a function is not defined withing the current serverless file you can still call it by providing an invoke url which should point to a REST method (must be post).
+
+```yaml
+custom:
+  appsync-simulator:
+    functions:
+      addUser:
+        url: http://localhost:3016/2015-03-31/functions/addUser/invocations
+      addPost:
+        url: https://jsonplaceholder.typicode.com/posts
+```
+
+
 # Supported Resolver types
 
 This plugin supports resolvers implemented by `amplify-appsync-simulator`, as well as custom resolvers.

examples/external-functions/mapping-templates/Query.getPosts.request.vtl

@@ -0,0 +1,4 @@
+{
+    "version": "2018-05-29",
+    "operation": "Invoke"
+}

examples/external-functions/mapping-templates/Query.getPosts.response.vtl

@@ -0,0 +1 @@
+$util.toJson($context.result)

examples/external-functions/package.json

@@ -0,0 +1,13 @@
+{
+  "name": "external-functions",
+  "version": "1.0.0",
+  "main": "index.js",
+  "license": "MIT",
+  "scripts": {
+    "offline": "sls offline start"
+  },
+  "dependencies": {
+    "serverless-appsync-plugin": "^1.3.1",
+    "serverless-offline": "^6.7.0"
+  }
+}

examples/external-functions/schema.graphql

@@ -0,0 +1,14 @@
+type Post {
+    userId: Int!
+    id: Int!
+    title: String!
+    body: String!
+}
+
+type Query {
+  getPosts: [Post]!
+}
+
+schema {
+  query: Query
+}

examples/external-functions/serverless.yml

@@ -0,0 +1,33 @@
+service: mapping-templates
+provider:
+    name: aws
+    region: eu-west-1
+
+plugins:
+    - serverless-offline
+    - serverless-appsync-simulator
+    - serverless-appsync-plugin
+
+custom:
+    appsync-simulator:
+        functions:
+            myLambda:
+                url: https://jsonplaceholder.typicode.com/posts
+                method: GET
+    appSync:
+        name: Test
+        schema: schema.graphql
+        authenticationType: AWS_IAM
+        mappingTemplatesLocation: mapping-templates
+        mappingTemplates:
+            - dataSource: MyLambda
+              type: Query
+              field: getPosts
+              request: Query.getPosts.request.vtl
+              response: Query.getPosts.response.vtl
+        dataSources:
+            - type: AWS_LAMBDA
+              name: MyLambda
+              config:
+                  functionName: myLambda
+                  lambdaFunctionArn: "arn:aws:lambda:${self:provider.region}:*:getPosts-graphql"

src/getAppSyncConfig.js

@@ -2,6 +2,7 @@ import {
   AmplifyAppSyncSimulatorAuthenticationType as AuthTypes,
 } from 'amplify-appsync-simulator';
 import { invoke } from 'amplify-nodejs-function-runtime-provider/lib/utils/invoke';
+import axios from 'axios';
 import fs from 'fs';
 import { forEach } from 'lodash';
 import path from 'path';
@@ -60,6 +61,24 @@ export default function getAppSyncConfig(context, appSyncConfig) {
           );
           return null;
         }
+
+        const conf = context.options;
+        if (conf.functions && conf.functions[functionName] !== undefined) {
+          const func = conf.functions[functionName];
+          return {
+            ...dataSource,
+            invoke: async (payload) => {
+              const result = await axios.request({
+                url: func.url,
+                method: func.method,
+                data: payload,
+                validateStatus: false,
+              });
+              return result.data;
+            }
+          }
+        }
+
         const func = context.serverless.service.functions[functionName];
         if (func === undefined) {
           context.plugin.log(
@@ -68,6 +87,7 @@ export default function getAppSyncConfig(context, appSyncConfig) {
           );
           return null;
         }
+
         return {
           ...dataSource,
           invoke: (payload) => invoke({