It came up when fixing bug 19907 that we don't propagate any exception information in an NPAPI callback. The NPAPI reference suggests that we should return false, at least in some cases: http://developer.mozilla.org/en/docs/Gecko_Plugin_API_Reference Some compatibility testing will be required, because the NPAPI documentation isn't very specific.
Related to Bug 18234?
(In reply to comment #1) > Related to Bug 18234? Yes, that bug should probably depend on this one, or maybe even be marked a duplicate. There is now no real support for NPN_SetException.
From Webkit Github mirror, I am only able to find following references about NPN_SetException: https://github.com/WebKit/WebKit/blob/25eed588cb7fcdb340b0783e2c2c7022cd48897a/Source/WebCore/bridge/testbindings.cpp#L148 I think all other references of it are removed as part of NPAPI removal, since it is not supported from Safari 14 onward and also not supported on WebkitGTK port. I think any further enhancement to NPAPI is not in radar and this can be marked as "RESOLVED WONTFIX". Thanks!
<rdar://problem/95544910>