With regard to the first point, the examples may be hypothetical, but they are also very plausible.
When a change has little or no objective benefit, I feel the burden of demonstrating that it is harmless falls on those making the change.
As has been pointed out elsewhere, this is free software and the maintainers are free to do whatever they like. That does not stop others having an opinion about it, especially when it is in the form of constructive criticism.
Sure, but it would still be nice to have at least one such example. Looking at the rest of the discussion thread here on HN as of now it's still only hypotheticals.
But it changes the behavior of the script in the UI. It can cause things like cron to send mail. It can cause other things wrapped around the script that are capturing both STDOUT and STDERR from the script to capture extra content. Any tool that's monitoring STDERR and expecting it to be empty may consider that an erroneous run, which may impact other scripted decisions. It's a breaking change in multiple circumstances, even if you don't consider extraneous warnings shown to a user manually running a script a breaking change.
Does that code look like something you'd log into a system and manually run on a regular basis? Does it maybe instead look like one layer of a legacy automation stack absorbed into other tools?
Using that model, we can prove conclusively that, since a behavior has changed (a warning printed), it might cause problems. Therefore, we cannot prove that it cannot cause problems. What we would really like, though, is an actual problem shown to exist. Just like in mathematics; it’s one thing to prove that it’s impossible to prove something could not exist, but another thing entirely to show it existing.
You are overlooking something here: I never said anything about proof. I explicitly wrote 'convincing evidence' because proof is too demanding!
It's rather amusing how you have flipped from saying "you can't prove a negative" to an argument for the certainty of observable effects and the probability of consequences! (you wrote might cause problems, but everyone can see that's an unrealistic understatement of the implications of the argument you are using.)
The NASA managers prior to the Challenger crash thought that what they really wanted was something showing them an actual problem existed. Erring on the side of caution is generally prudent, even in relatively small matters.
> everyone can see that's an unrealistic understatement of the implications of the argument you are using
If nobody can show an actual existing problem, or even an example of reasonable code someone could have written which would be impacted by a the printed warning, then yes, I would think that I was charitable when I wrote “might cause problems”.
What does 'charitable' mean here? Generous towards what person or point of view? As you say you have conclusively proved that there is a non-zero probability of there being problems, the use of 'might' is already trying to persuade that this possibility is next to zero.
Yes, of course. If the case is reasonably likely to occur in the real world and have real world impact, that is. And I would assume that the GNU grep developers would agree with me.
I think that is a very reasonable position to hold. It would only be the rejection of plausible cases, on the basis of no actual case having been uncovered, that I would take issue with. When assessing the downside of a proposal, there should not be much, if any, difference between how highly plausible and certain consequences are assessed.
If we could prove there would be no downside, then plausible problems could be ignored as merely hypothetical, and there would be no need to posit offsetting benefits. The question the GNU grep developers might want to consider is whether the supposed upside will have sufficient material consequences for their purposes.
When a change has little or no objective benefit, I feel the burden of demonstrating that it is harmless falls on those making the change.
As has been pointed out elsewhere, this is free software and the maintainers are free to do whatever they like. That does not stop others having an opinion about it, especially when it is in the form of constructive criticism.