The stuff that has bit me I think is:

  • Enumerations where I don't know what the range of valid values is or what they mean and when to use them (like visibility, IIRC)
  • Type-shifting values that might be Boolean false or be an actual (numeric, usually, IIRC) value.

Both of those are basically the same problem: What things can show up under this key, when, and what do they mean? Observing the posts and such that I can see never guarantees I saw all the cases.

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