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I've been trying to debug an issue for 3 days now, am getting nowhere, and am about to headbutt my laptop. If anyone's done any heavy lifting with Net:DBus then, for the sake of my laptop, I'd really appreciate the help!

Problem description: I have a hash table with a bunch of keys. The values relating to those keys are of different types (as in, I've cast them to dbus types). So:

my $testhash = {}; $testhash->{"xesam:albumArtist"} = [dbus_string("Tom Waits")]; $testhash->{"xesam:album"} = dbus_string("Mule Variations"); $testhash->{"xesam:trackNumber"} = dbus_int32(1); $testhash->{"xesam:artist"} = [dbus_string("Tom Waits")]; $testhash->{"xesam:title"} = dbus_string("Big in Japan"); $testhash->{"mpris:artUrl"} = dbus_string("file://mnt/storage/Music/mp3/Tom Waits/Mule Variations/folder.jpg"); $testhash->{"mpris:length"} = dbus_int64(64182857); $testhash->{"mpris:trackid"} = dbus_object_path("/0"); $testhash->{"xesam:url"} = dbus_string("file://mnt/storage/Music/mp3/Tom Waits/Mule Variations/01 - Big in Japan.mp3"); 

I've created a DBus service, and have successfully implemented a method that returns that hash table ($IFACE is the interface name I'm using for all of my test methods):
dbus_method("ReturnDynamicHash", [], [["dict", "string", ["variant"]]], $IFACE); sub ReturnDynamicHash { my $self = shift; print "Object: ReturnDynamicHash called.\n"; my $return = {}; my @keys = keys(%{$testhash}); my $count = scalar(@keys); if ($count) { foreach my $key (@keys) { $return->{$key} = $testhash->{$key}; } } return $return; } 

As a DBus method, this works perfectly:
% dbus-send ....... .ReturnDynamicHash array [ dict entry( xesam:trackNumber variant int32 1 ) dict entry( mpris:trackid variant /0 ) dict entry( xesam:albumArtist variant array [ Tom Waits ] ) dict entry( xesam:album variant Mule Variations ) dict entry( mpris:length variant int64 64182857 ) dict entry( xesam:url variant file://mnt/storage/Music/mp3/Tom Waits/Mule Variations/01 - Big in Japan.mp3 ) dict entry( mpris:artUrl variant file://mnt/storage/Music/mp3/Tom Waits/Mule Variations/folder.jpg ) dict entry( xesam:artist variant array [ Tom Waits ] ) dict entry( xesam:title variant Big in Japan ) ] 

However, the interface I'm implementing requires that a DBus Property return that hashtable, not a method:
dbus_property("StaticHashProperty", [["dict", "string", ["variant"]]], "read", $IFACE); sub StaticHashProperty { print "Object: StaticHashProperty accessed.\n"; my $return = {}; my @keys = keys(%{$testhash}); my $count = scalar(@keys); if ($count) { foreach my $key (@keys) { $return->{$key} = $testhash->{$key}; } } return $return; } 

and this doesn't work.

From the dbus-send client I get

Error org.freedesktop.DBus.Error.NoReply: Remote peer disconnected 

and from the Perl server stderr i get:
dbus[93409]: Array or variant type requires that type array be written, but object_path was written. The overall signature expected here was 'a{sas}' and we are on byte 4 of that signature. D-Bus not built with -rdynamic so unable to print a backtrace Aborted (core dumped) 

Now, this error is coming from libdbus itself, not the Perl wrapper (though could of course still be a bug in the Perl module that's causing the error). It seems to have entirely the wrong signature ( a{sas}, not a{sv} as defined above the Property method) and therefore appears to be complaining that the type of one of the values is wrong (each time I run it I get a slightly different error; I think it's deducing the signature from the first key-value pair it pulls from the hash and assumes they should all be the same - so if the first pair it pulls has a uint64 value, then it complains that the next pair doesn't also have a uint64 value).

Since the Method works I know Net::DBus can handle these sorts of return values, but for some reason, as a property, it just isn't working. I also know that other applications do implement this interface, including this Property, successfully, so I know this isn't a limitation of DBus.

I've been looking at the code in Net::DBus that handles serialization, assuming there must be some difference between how Properties and Methods are handled, but can't see anything obvious.

Anyone? Any idea? Literally anything at all? Thank you!!!!!

submitted by /u/Flashy_Boot
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