Errors are values, but only if you treat them that way

Thu, 14 Nov 2024 17:10:00 +0100

Last time I argued that a function’s signature should never lie. The error return is the most lied-about part of every Go signature I read. It gets logged, swallowed, repackaged, panicked on, and printed back to the user as internal error: internal error: internal error. Three habits keep it honest.

Self-explained function signatures

Thu, 26 Sep 2024 08:45:00 +0100

A function I once shipped looked like this:

func Process(data []byte) error

Innocent. You give it bytes, it returns an error. What more do you need?

Plenty, as it turned out. Process also wrote a file to /tmp, posted the same bytes to a webhook, and stashed a copy in a package-level global so the next call could “diff against the last one”. None of that was in the signature. None of it was in the doc comment either, because by the time anyone read the doc comment they’d already wired the function into a hot path and were wondering why CI was flaky.

The signature lied. Once a signature lies, every reader has to open the body to find the truth. That’s the cost.

Clean Code on Segflow

Errors are values, but only if you treat them that way

Self-explained function signatures