set_exception_handler invokes the handler but still show the fatal error msg

[ghost]

The following code should print Only print this message: User message here.

set_exception_handler(function($e) {
    echo "Only print this message: " . $e->getMessage();
});

throw new Exception("User message here.");

But instead it produces

Fatal error: Uncaught exception 'Exception' with message 'User message here.' in test.php:7
Stack trace:
#0 {main}
Only print this message: User message here.

[milo]

This behaviour can be disabled by hhvm.log.always_log_unhandled_exceptions=false.

[paulbiss]

@milo is correct

$ hhvm -vLog.AlwaysLogUnhandledExceptions=false test.php
Only print this message: User message here.
$

[SiebelsTim]

@paulbiss This is a workaround and no fix, isn't it?

[paulbiss]

Should the trace always be suppressed when an exception handler is defined?

[SiebelsTim]

@paulbiss Well it isn't an uncaught exception. set_exception_handler is supposed to mimic a catch I think.

[paulbiss]

I dug into this today, we only check AlwaysLogUnhandledExceptions in two places and it's precisely to define this behavior. It seems to me that the intent here is to treat exceptions that arrive at the exception_handler this way unless the flag is set to false.

If you think we should choose a different default feel free to open another issue, but insofar as I can tell this is by design, the flag is there if you want parity with PHP5.

[Majkl578]

@paulbiss: Maybe it should be off by default to match PHP?

[paulbiss]

@Majkl578 we'd consider a pull request for it. You'll probably have to add ini settings for tests we have that assume it's on and we'll need to update our configs internally.

[Majkl578]

@paulbiss: Let's have some compatibility fun. :) #4066 (D26997)