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catch exception from iw_load_dcr

yanSi

If I provide iw_load_dcr with a path to a dcr that cannot be loaded, the pt compiler will not compile the page and display an error. Is there a way for me to catch the exception and handle it?

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Comments

Migrateduser

Rather than use the iw_load_dcr tag, do the loading inside an iw_perl tag. Wrap the call with an eval(), and check the value of $@ after the call. If it failed to load, take whatever defensive action is appropriate.

Or, if you want to go overboard with it, use Error.pm:

http://www.perl.com/pub/a/2002/11/14/exception.html

yanSi

I'm using this line within an iw_perl block:
eval {$s=iwpt_load_dcr($file, $mode);}; $badDCR="bad" if $@;

To me, this line of code says that if the iwpt_load_dcr is unsuccessful, the $@ variable will contain the error message from the iw pt compiler and I will assign the variable $badDCR the value of "bad". If iwpt_load_dcr is successful, $@ will contain null and no operation is performed.

The iw pt compiler still generates the error message "Could not load dcr..." after I do this and it's not being handled by eval so I see the error message when I do a preview. Why didn't that work?

I guess my next option is to get the full path to the dcr and try to see if it exists before calling iw load dcr.

Adam Stoller

I think the code should be something like:

my $s = q{};
eval {
  $s = iwpt_load_dcr($file, $mode) 
      || die "Unable to load DCR '$file' ($mode)";
};
if ($@){
die $@;
}

I'm not sure if this will do everything you want, but I think it will work a bit better.

Migrateduser

I'm not surprised to see it put the error to stdout, but it is a little surprising that it doesn't catch the error. All I can figure is that they don't actually raise an error code. I'm starting to have vague memories of having run into some similar problems with error trapping in PTs. Try compiling to ocode and see what the resulting perl looks like. It may also be interesting to see if it will catch the exception properly at the command line but not when run in the context of TeamSite: Smiley Tongue Tparser.

Interestingly, the PTparser object contains a member called "eval_error", so it may be possible to manipulate that from within your PT. If you can, doing so would definitely not be a supported approach, though.

jbonifaci

Adam, since when is dieing without any error handling a good thing?

Migrateduser

I see the problem now - deeply embedded in the stack, inside the iw_xml module is this little gem:

[PHP]696: if ( !($iw_xml_load_dcr = $iw_parser->open_osenc($file)) )
697: {
DB<2> n
TeamSite: Smiley Tongue

T::iw_xml::load_dcr(C:\Interwoven\TeamSite\iw-perl\vendor\lib/TeamSit
e/PT/iw_xml.pm:698):
698: TeamSite: Smiley Tongue

Tparser::error( "Could not load dcr: $file" );
[/PHP]

So, rather than doing a nice clean croak or die, they call some error function of their own. If you look at PTparser, it calls exit at the end of the error function rather than die, so it may be that eval thinks the interior code execute fine and didn't need to be trapped.

If you want to try hacking it a bit, make a backup copy of PTparser.pm and change line 1525 to
[PHP] die $error{exit_status};[/PHP]

That gave me the behaviour I expected. Naturally, doing something like this is completely unsupported, and I make no warranties, express or implied. If you follow my advice and bad things happen, it's your fault for following my advice. Smiley Happy

Adam Stoller

Adam, since when is dieing without any error handling a good thing?

Normally - it isn't - but since the PT engine is largely out of our control I was just trying to get it to a point where you could truly capture the error. However, apparently (as per other recent posts) the issue is a bit more embedded within the PT code and it isn't clear that my posted code would work any better than the previously posted code which I modified.

yanSi

Thanks for your help Rob and Fish. I'm just going to use eval to check if the file can be opened first before calling iw load dcr.

eval{
open (DCR, $pathToFile) || die "couldn't open the file!";
};
$badDCR="bad" if $@;

ISCBorisB

Thanks for your help Rob and Fish. I'm just going to use eval to check if the file can be opened first before calling iw load dcr.

eval{
open (DCR, $pathToFile) || die "couldn't open the file!";
};
$badDCR="bad" if $@;

It may be benefitial not to use "die" in your presentation template at all.

It'll die all right, in Windows however subsequent view/generate attempts may result with infamous "broken pipe" error
in some cases. Better log an error or run some CGI to show error to your Content Contributor, something of that nature...