The error message “Domain error in arguments” could be more informative

[ZhihuiChen0903]

The error message “Domain error in arguments” seems too general to be informative.

C:\ProgramData\Anaconda3\lib\site-packages\scipy\stats\_distn_infrastructure.py in rvs(self, *args, **kwds)
    938         cond = logical_and(self._argcheck(*args), (scale >= 0))
    939         if not np.all(cond):
--> 940             raise ValueError("Domain error in arguments.")
    941 
    942         if np.all(scale == 0):

After reading the source, I believe that the expected behavior is that shape parameters should be positive and scale should >=0. Adding this information to the error message should be more user-friendly.

Expected error message:
Domain error in arguments: shape parameters should be positive and scale should >=0.

[rgommers]

Thanks @ZhihuiChen0903. A better error message would be nice, but unfortunately this change is not correct - distributions define their own _argcheck that overrides the default one, so it's not just "must be positive". There's no easy way to get this right I'm afraid.

[mdhaber]

No need for this to wait. I don't imagine there will be problems, but I'll re-run CI (close and re-open) and merge if it's green.

[mdhaber]

Might be helpful to use an f-string to mention the name of the distribution (e.g. "see weibull_min documentation"), and perhaps it should be phrased so that it's more clear that scale is not necessarily the problem. But maintainer's requested change has been addressed, lint passes, and this is more informative than it was, so merging.

Thanks, @ZhihuiChen0903! Next time, please create a feature branch instead of using master (now main) for PRs, but thanks for submitting this.