Introduction

Edge cases in programming, or in engineering generally, are the extreme cases or scenarios expected in a system. If a system has enough edge cases, you could handle or cater for whenever the system behaves in an unusual way.

A day-to-day example is: The output sound of a speaker could be distorted at the highest volume.

Other, more technical examples can be: Handling a credit count when the credit gets to zero (0). At that point the user should not be able to use credit or deduct it; however, if you do not handle that scenario, you could start getting a negative count on the credit.

When Stackoverflow can't help...

As established above, edge cases are rare, almost impossible situations in a system as such the solutions to those situations are next to impossible to find.

When I ran into the Uncaught TypeError and my GraphiQL interface was not coming up on my local machine, I quickly ran to Stackoverflow. Surely, someone must have had this before and it must have been solved. Well....nope.

What did I do?

I did a lot of Google searches throughout the first day of this issue and tried many different things all to no avail.

When dealing with edge cases, there is not much you can do except...restart the system. In my case, I finally resolved to change the port from which I was serving my Django App. I chnaged the port from the default 8000 to 8002; Immediately that solved the issue.

What was the error?

Uncaught TypeError: Cannot read property 'subscriptionPath' of undefined.

Till today, I have no idea what it means. If you have run into a similar issue, well here is the simple solution: Restart the system (application) and serve it from a different port.

Conclusion

Edge cases are uncommmon, however, it is definitely something to always look for and deal with as appropriate.

If you are faced with an edge case, resolve to restart the system, it just might be what solves the issue.

Thank you for reading till the end.

Till next time,
Oluwadara, OLOYE.