等待Python警告并引发异常

Question

I have a Python test that possibly generates many warnings. When the test finishes, I want it to raise an exception if there were any warnings.

It is important to run the test to the end and then raise, because I am using a remote build bot and want to see all warnings at once.

How do I do that?

Answer 1

I asked that yesterday but found the answer later, alone. The technique is interesting and I want to share it.

When a module creates warnings with the warnings module, it stores these warnings in a special variable that holds the seen warnings. So in my case, the parser module issues warnings. I simply let it do its usual job, and at the end of the test comes:

if hasattr(parser, "__warningregistry__"):
    raise RuntimeError("There are errors, see above.")

This way, I don't have to modify my parser in any way, but at the end of the run, I get an exception, and I have all warnings available. Then I can fix all cases and start another run of the build bot.