Make -P (pdb) work better with exceptions triggered from events

[jbms]

Feature or Bugfix

• Bugfix

Purpose

Previously, if an exception was raised from an event listener, and the
-P option was specified, the debugger would be started not for the
original error but for the ExtensionError wrapping it that was
raised by EventManager.emit. That made it difficult to debug the
error.

With this change, when -P is specified, wrapping of errors in
ExtensionError is disabled, which allows pdb to debug the original
error.

[AA-Turner]

+1 on the idea.

Is it possible to implement this without adding a new attribute to Sphinx? The application object already has a really big API.

This would also need a CHANGES entry.

A

[jbms]

I think it is difficult to avoid making it a parameter to Sphinx.__init__, since some events are emitted by Sphinx.__init__ so it would be too late to enable it later. In principle it could be passed as a separate parameter to EventManager.__init__ by Sphinx.__init__, since currently the variable is only used by EventManager, though I'm not sure that is an improvement, and I think it is possible that we will find other code in Sphinx that is currently wrapping exceptions and needs to be changed (and will then need access to this variable).

[jbms]

I added a changelog entry.

[tk0miya]

LGTM :-)