Error messages

[Peter230655]

Today, by accident, I had an instance_constraint for a state variable, which I had replaced with an eom_bound, so it no longer existed.
I got some error message which did not point to this problem at all.
My question: If I come across something like this, is it o.k. to suggest a way to raise an error which points the user to the problem?

[Peter230655]

@moorepants : Since you may be getting closer to releasing the next opty, I'd like to raise this again. My feel is that such error messages may prevent an inexperienced uses to go on a wild goose chase.

[moorepants]

We should give informative error messages in general, but we also fall back to "garbage in, garbage out" vs creating overly extensive error checking. There is also the question of whether sympy, opty, cyipopt, ipopt, cython, etc should be issuing the error message and we should put the error checking in the appropriate library versus load opty (the top most library) with all the error checking. In some sense there are an infinite number of wrong things a user can give to opty, but we aren't going to make infinite error checking. So if something is a likely common error a user may make and the checking belongs in opty, not in one of the underlying libraries, feel free to propose it in a PR.

[Peter230655]

I see your point - but I am putting myself into the shoes of an opty user - which I am.
YES, there is an inumerable number of ways opty can be fed the wrong stuff, and no way we can prevent this, not in finite time.
I report the stupid inputs, where the error messages gave me no clou of what I'd dome wrong - with my time on hand, I eventually figured it out.

It is probably a rare thing to happen: You'd have to declare a state variable, which does not appear in the eoms and then bound it.
Likely as rare as what I noticed some time ago: backend='numpy' and only one par_map, and this one value being an integer. We dropped this, too.

[moorepants]

I will accept most error checking PRs as long as it doesn't slow things down a lot.

[Peter230655]

Clear. So if I think, it is fast and worthwhile, I can push and you will merge or close as you see it.
Probably the best way. (As you know, I am not offended at all if I push something an you close it)