[ninkendo]

One should always imagine a 1000:1 ratio of “person who reads a warning message” to “person who can do anything about it”.

You drop a little stderr print in your library saying “foo is deprecated, please use bar”, but then that library is included in another library which included in a CLI called by a script somewhere and, now the output goes to someone’s terminal when they’re running some management CLI. They never wrote the call to foo, they don’t even know what a foo is, they are 3 layers removed from who the target audience is.

Runtime is never the time to alert to things like deprecations or “this shouldn’t be used this way” notices. For deprecations, use your language’s built-in way of making functions deprecated. If your language doesn’t have that, use a real programming language. For other types of warnings, if you’re not 100% sure your message will only be seen by the developer who can fix it, just don’t write it.

[moring]

Bonus points for the kafkaesque responses you get as the end-user when you try to actually pass that information upstream where it could be fixed...