Re: [PATCH RFC3.5 08/12] send-email: Move Subject sanitization from --compose code to send_message

On Sun, Apr 19, 2009 at 09:39, Michael Witten [off-list ref] wrote:

I'm morally opposed to this kind of thing. The caller should be
required to test whether quote_rfc2047() is required, as it's not the
job of quote_rfc2047 to validate. Suppose that quote_rfc2047 were
actually part of a library of useful functions that my program
imports. Perhaps my program knows that it must always quote some piece
of text. Why, then, should my program be forced to waste the cycles to
perform a useless test?

IMnsHO, verification should always be done by the caller with one
exception: Interactive (human) input should always be verified,
because humans represent an unreliable component in the system (in
terms of digital systems, their asynchronous input must be
synchronized with the clocked system). WIth this model, there's are
fewer wasted cycles, because you can reuse verification across similar
functions, and the code (particularly library code) is easier to
understand.

I should add, though, that making the logic of the program clear is a
good idea. In that sense, your approach makes sense. Since we 'own'
quote_rfc2047(), I'd say we could take your approach, but rename the
function to something like quote_rfc2047_if_necessary(). If
quote_rfc2047() were part of a library, I think the only moral
solution would be to insist that callers wrap it in another function
named quote_rfc2047_if_necessary().