Created attachment 184068 [details]
test_signal.vala

valac 0.11.7.7-6929

I cannot declare a variable of type HashTable<string,string[]?> because I get the error:

error: `string[]?' is not a supported generic type argument, use `?' to box value types

I tried without success several syntaxes: with or without the "?", with GStrv.

According to juergbi, it is not supported in a native type. Emitting D-Bus signal are difficult because I have to build the variants manually and use:
conn.emit_signal ("bus.name", "/path", "iface", "signalName", variant)

Using [DBus (signature = "a{sas}")] does not work neither because I get an critical error:

(process:32429): GLib-CRITICAL **: g_variant_builder_add_value: assertion `!GVSB(builder)->expected_type || g_variant_is_of_type (value, GVSB(builder)->expected_type)' failed

The attached program illustrates the problem.