Extending Flow with Functions - Part 2

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Very often there are packages out there, that we could use to extend our flow with more functionality.

In this article I will show you how to extend flow, using Azure Functions. The technique I'm going to use is:

Create an Azure Function that take some input, does some processing, and returns a result;
Test the function to show how it works as an API;
Write a custom connector, so we can integrate with Flow (and PowerApps);
Use it in Flow

In the first Part of this series, we created the Azure Function, and now in the second part, we will write the custom connector and use it in Flow.

Custom Connector- here we go

A Custom Connector is way for us to define an interface for Power Platform to communicate with our API - which in this case is the Function App we just created. We define this using OpenAPI 2.0 (formally swagger). There are a lot of tools out there to help you create your OpenApi(such as OpenApiGen), but for this we just going to create it using the swagger editor to create it.

Change the following parts of the OpenApi:

host - set the host to the url of your azure function app
```
host: "liquid-flow.azurewebsites.net"
```
basepath - set this to the base of the function app, by default will be /
```
basePath: "/"
```
schemes - function apps only use https
```
schemes:
- "https"
```
Add the function, so path is /api/Liquid
```
/api/Liquid:
```

Parameters have a body

 parameters:
 - in: "body"
 name: "liquidbody"
 description: "Liquid Transformation"
 schema:
 $ref: "#/definitions/LiquidBodySchema"

Response will have return an object

responses:
 200:
 description: "OK"
 schema:
 $ref: "#/definitions/LiquidResponseSchema"

Add the request schema

definitions:
 LiquidBodySchema:
 type: "object"
 properties:
 liquidtemplate:
 type: "string"
 description: "The Liquid Template to transform"
 x-ms-summary: "Liquid Template"
 data:
 type: "object"
 description: "Data to transform"
 x-ms-summary: "Data"

Add the response schema
```
 LiquidResponseSchema:
 type: "object"
```
By returning just an object, anything can be returned in the response

Get the JSON version, by choosing "Convert and save as JSON" from the File menu

Here are the completed files:

Add the custom connector

Lets upload our OpenApi file into PowerApps, so in PowerApps, select Data - Custom connectors

Click on the right hand side "Create custom connector"

Connector name is Liquid Templates, and add the OpenApi file

Click Create Connector and it will create the custom connector.

Test the connector

To test the connector, click on the Test tab

Create a New connection, and then put some test data into the two field:

Click the Test operation button, and you should get the result back.

NOTE: If have just created the connection, and you get a Operation failed (404), see response below error, it doesn't mean you have an error - it's PowerApps way of telling you its still setting everything up - go get a coffee and come back in 10 or 15 minutes time. Hopefully by then PowerApps has setup all the bits to get the custom connection done, and you'll get your 200 response with the output.

So we now have: