Report on uncatchable exception handlers (?)

[jakkdl]

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Was surprised bugbear didn't report this, but not encountered in live code so I don't know if it's seen much / ever in the wild:

try:
  ...
except BaseException:
  ...
except:
  ...

will report B001/E722, but in a project that uses bare excepts widely and disables those checks the except never being possible to run seems like a separate error.

try:
  ...
except BaseException:
  ...
except Exception:
  ...

Gives no warning, nor does a plausibly more common

try:
  ...
except Exception:
  ...
except ValueError:
  ...

or similar variants. Checking whether a caught exception is a built-in, and if so issubclass of a previously caught exception, seems straightforward. I quickly checked mypy and vulture as well and neither of them sees it. But this might definitely not be common enough that it's worth bothering with.

[JelleZijlstra]

For what it's worth, Pyright/Pylance catches this:

[jakkdl]

For what it's worth, Pyright/Pylance catches this:

It does not catch bare except after a BaseException (and since py3 exceptions have to inherit from baseexception), but indeed looks like it catches the other ones.

[cooperlees]

If nothing catches Exception (and children) being caught/except after BaseException, I think this is worth a check. BaseException catching in general is even more evil than Exception and I generally won't approve PRs that do it ...

I also like it checks all other exceptions too, as not everyone runs VSCode / IDE with this detection.