I once made an oopsie in an API for a logistics provider (one of the biggest in Germany...).

To understand the oopsie...

Based on input data a string must be created containing several hex / string / formatted values.

Think of ...

$return .= sprintf("%02X", ...)

I think there were around 15 to 20 lines, although more complicated.

The bug happened because I had a brainfart.

What was previously one line with... Many many many many variables, I had to split into multiple lines since internal stuff changed and it was impossible to change this oneliner of hell with >50 formatting codes.

Of course we didn't test everything.
XD

What we didn't test was - funnily enough - wether the casting was correct in all cases.

I misplaced a formatting code.

And we had a major brainfart because we tested integer, but not double / float values....

We sent for a long time packages much cheaper than allowed (took thw logistics provider nearly 3-4 months to realize this :) ).

Spot the difference:

@highlight
print sprintf("%01.2s", $money).PHP_EOL;

print sprintf("%01.2f", $money).PHP_EOL;

5k lines of code and some long days in and it turns out UI and I (backend) had an oopsie in our communication so it was all for nothing. Back to 0😖

MFW I worked longer than 8 hours because of a weird bug that turned out to be caused by lack of typing in a third-party library. Was supposed to be a number but I was giving it a string 🤦‍♀️Need more sleep.

The funniest part is the library was written in Typescript. HmmMMMMmm...

Throw a `parseInt` or warning for wrong type in there for me, fellow devs! Save consumers of your library a headache!!