Peak "how did this ever work" today in PHP land. I was debugging a method that was improperly returning an empty array. Dig into the code ... and found that it was hard-coded to do so.
But oh! Polymorphism meant a subclass had a non-empty-returning implementation.
Yet that was still improperly returning an empty array.
Ultimately, the very innermost method was returning an array with the wrong schema, which caused subsequent lookups to be blank.
A one-line fix got it working.
Lessons:
1. Remember to write tests
2. Tests will lie to you if you're not careful
3. Code can look correct yet still be silently wrong
4. Silently-wrong code can be live for months or years with no one noticing
5. Computers were a mistake. I need a sailboat and a long break from everything.
