Dynamics Code

This post is more of rant than evangelist.

In October 2018, I had involuntarily involved in developing Power Apps for one of our clients at work. “Why involuntarily?” you may ask. Well, although I mainly work with Microsoft platform, I play around with iOS and Android native app developments and help out my friends. So, I fairly know the biggest challenge with mobile app development, making your app to work across different devices.

Power Apps is great. I have no doubt about it. All canvas-apps run inside Power Apps native app on your mobile, thus making it very different from cross-platform development in mobile app. It also means you have no control over the release of Power Apps native app.

Regardless of my strong objection, we managed to deliver the app in 10 days. The purpose of the app is to transform their paperwork of auditing farms. Basically, admin will create audit records in D365 and assign to auditors, then auditors will download records to their apps for offline use, drive out to remote areas for auditing (which also captures photo and signature). When auditors arrive back to their home at night, they sync their offline data to D365 and get newly assigned audits. Photos need to upload to their Google Drive. Why not? Microsoft Flow has out-of-the-box connector to Google Drive. Easy peasy.

Then, the client wanted to add a new functionality which will share photos uploaded in Google Drive to the audited farm. Although you can share files/folders in Google Drive, out-of-the-box connector is not capable of doing it. After going through Google Drive REST APIs, we solved it by creating a custom connector. To deliver all these functions in 10 days was impressive. It was working fine. Well … for two months.

In December, the client told us some of their auditors were facing issues with syncing records. We enhanced our app for a better performance. During the enhancement, it was all fine. When the app was re-opened again, it showed over 200 errors on one of global variables in the app. Suddenly! Set and Patch function on record type global variable didn’t work anymore. (You can find the similar issue here, though I didn’t report it).

I ended up with re-creating an app almost from scratch again. Tweak and fix. Again and again. One of the challenges with web player is you can’t test offline mode. SaveData and LoadData doesn’t work. I hope Microsoft will at least create stubs for these two functions for web player in the future. Having to test it on the device, you have to publish the app, and open the app at least twice in the device to see the latest version. It is not productive at all, but we managed to fix all issues.

But, there was another problem. Microsoft has released the new version of Power Apps and unfortunately it was a bad version. Without noticing the bad version, I kept working on the app. After publishing to test it on my device, it was too late. There was no way to return. If I rolled back to the working version, all my changes will be lost. If I stick to the current version, it can’t be tested. It didn’t look good at all.

Luckily, Microsoft released the bug fix over the weekend and the original issue was gone. But, again, the app was starting to behave weird. Functionalities used to work were not working anymore. For example, if I rolled back to the old working version, it worked. But, not on the latest Power Apps version. It is so frustrating for a developer. You have no control over which Power Apps runtime you want to choose. Microsoft dictates it. Because of it, one bad runtime version can create many issues even if you don’t make any changes.

During the enhancement, we started to notice errors in listing Google Drive files in Microsoft Flow. After searching Google Drive REST APIs, it turns out Google limits items returned from API to 100 by default and it can be changed. However, there is no way to define the paging size in out-of-the-box connector. We didn’t have the issue in UAT and early days of production go-live since items were less than 100. But, now we have an issue. As usual, a custom connector saved our life.

All issues seem to be sorted out, at least, for now. Hopefully, the app will behave nicely for next two months. But, I learned following lessons.

• Power Apps is easy but not necessarily simple – a lot of gotcha and similar functions with totally different behaviours.
• A lack of ability to control Power Apps version – one bad version will break your app into pieces just by publishing without making any changes. If it happens in development phase, it will stale the timeline.
• Out-of-the-box connectors are useful for demo but not reliable for production – always reference to the source API documentation, not Microsoft Flow documentation.
• Community is great but not all issues are resolved – looking at the example with Set and Patch functions in above link, it took about 2 months to recognise the issue by Microsoft Power Apps team. The worst part is it is not resolved yet.