Added basic variant type support

This also enables reading properties of DBus interfaces.

Readme.md

@@ -42,6 +42,21 @@ auto name = obj.GetNameOwner("org.freedesktop.DBus").to!string();
 obj.call!string("GetNameOwner","org.freedesktop.DBus");
 ```
 
+### Working with properties
+
+```d
+import ddbus;
+Connection conn = connectToBus();
+PathIface obj = new PathIface(conn, "org.freedesktop.secrets", "/org/freedesktop/secrets/collection/login", "org.freedesktop.DBus.Properties");
+
+// read property
+string loginLabel = obj.Get("org.freedesktop.Secret.Collection", "Label").to!string();
+loginLabel = "Secret"~login;
+// write it back (variant type requires variant() wrapper)
+obj.Set("org.freedesktop.Secret.Collection", "Label", variant(loginLabel));
+```
+Setting read only properties results in a thrown `DBusException`.
+
 ## Server Interface
 
 You can register a delegate into a `MessageRouter` and a main loop in order to handle messages.

source/ddbus/conv.d

@@ -28,6 +28,12 @@ void buildIter(TS...)(DBusMessageIter *iter, TS args) if(allCanDBus!TS) {
         buildIter(&sub, x);
       }
       dbus_message_iter_close_container(iter, &sub);
+    } else static if(isVariant!T) {
+      DBusMessageIter sub;
+      const(char)* subSig = typeSig!(VariantType!T).toStringz();
+      dbus_message_iter_open_container(iter, 'v', subSig, &sub);
+      buildIter(&sub, arg.data);
+      dbus_message_iter_close_container(iter, &sub);
     } else static if(basicDBus!T) {
       dbus_message_iter_append_basic(iter,typeCode!T,&arg);
     }
@@ -36,6 +42,15 @@ void buildIter(TS...)(DBusMessageIter *iter, TS args) if(allCanDBus!TS) {
 
 T readIter(T)(DBusMessageIter *iter) if (canDBus!T) {
   T ret;
+  static if(!isVariant!T) {
+    if(dbus_message_iter_get_arg_type(iter) == 'v') {
+      DBusMessageIter sub;
+      dbus_message_iter_recurse(iter, &sub);
+      ret = readIter!T(&sub);
+      dbus_message_iter_next(iter);
+      return ret;
+    }
+  }
   static if(isTuple!T) {
     assert(dbus_message_iter_get_arg_type(iter) == 'r');
   } else {
@@ -60,6 +75,10 @@ T readIter(T)(DBusMessageIter *iter) if (canDBus!T) {
     while(dbus_message_iter_get_arg_type(&sub) != 0) {
       ret ~= readIter!U(&sub);
     }
+  } else static if(isVariant!T) {
+    DBusMessageIter sub;
+    dbus_message_iter_recurse(iter, &sub);
+    ret.data = readIter!(VariantType!T)(&sub);
   } else static if(basicDBus!T) {
     dbus_message_iter_get_basic(iter, &ret);
   }
@@ -76,17 +95,19 @@ void readIterTuple(Tup)(DBusMessageIter *iter, ref Tup tuple) if(isTuple!Tup &&
 unittest {
   import dunit.toolkit;
   import ddbus.thin;
+  Variant!T var(T)(T data){ return Variant!T(data); }
   Message msg = Message("org.example.wow","/wut","org.test.iface","meth");
   bool[] emptyB;
-  auto args = tuple(5,true,"wow",[6,5],tuple(6.2,4,[["lol"]],emptyB));
+  auto args = tuple(5,true,"wow",var(5.9),[6,5],tuple(6.2,4,[["lol"]],emptyB,var([4,2])));
   msg.build(args.expand);
-  msg.signature().assertEqual("ibsai(diaasab)");
+  msg.signature().assertEqual("ibsvai(diaasabv)");
   msg.readTuple!(typeof(args))().assertEqual(args);
   DBusMessageIter iter;
   dbus_message_iter_init(msg.msg, &iter);
   readIter!int(&iter).assertEqual(5);
   readIter!bool(&iter).assertEqual(true);
   readIter!string(&iter).assertEqual("wow");
+  readIter!double(&iter).assertEqual(5.9);
   readIter!(int[])(&iter).assertEqual([6,5]);
-  readIter!(Tuple!(double,int,string[][],bool[]))(&iter).assertEqual(tuple(6.2,4,[["lol"]],emptyB));
+  readIter!(Tuple!(double,int,string[][],bool[],Variant!(int[])))(&iter).assertEqual(tuple(6.2,4,[["lol"]],emptyB,var([4,2])));
 }

source/ddbus/thin.d

@@ -26,6 +26,14 @@ T wrapErrors(T)(T delegate(DBusError *err) del) {
   return ret;
 }
 
+struct Variant(T) {
+  T data;
+}
+
+Variant!T variant(T)(T data) {
+  return Variant!T(data);
+}
+
 enum MessageType {
   Invalid = 0,
   Call, Return, Error, Signal

source/ddbus/util.d

@@ -1,6 +1,24 @@
 module ddbus.util;
+
+import ddbus.thin;
 import std.typecons;
 import std.range;
+import std.traits;
+
+template isVariant(T) {
+  static if(isBasicType!T || isInputRange!T) {
+    enum isVariant = false;
+  } else static if(__traits(compiles, TemplateOf!T) 
+                && __traits(isSame, TemplateOf!T, Variant)) {
+    enum isVariant = true;
+  } else {
+    enum isVariant = false;
+  }
+}
+
+template VariantType(T) {
+  alias VariantType = TemplateArgsOf!(T)[0];
+}
 
 template allCanDBus(TS...) {
   static if (TS.length == 0) {
@@ -25,6 +43,8 @@ template basicDBus(T) {
 template canDBus(T) {
   static if(basicDBus!T) {
     enum canDBus = true;
+  } else static if(isVariant!T) {
+    enum canDBus = canDBus!(VariantType!T);
   } else static if(isTuple!T) {
     enum canDBus = allCanDBus!(T.Types);
   } else static if(isInputRange!T) {
@@ -38,7 +58,7 @@ unittest {
   (canDBus!int).assertTrue();
   (canDBus!(int[])).assertTrue();
   (allCanDBus!(int,string,bool)).assertTrue();
-  (canDBus!(Tuple!(int[],bool))).assertTrue();
+  (canDBus!(Tuple!(int[],bool,Variant!short))).assertTrue();
   (canDBus!(Tuple!(int[],int[string]))).assertFalse();
   (canDBus!(int[string])).assertFalse();
 }
@@ -64,8 +84,8 @@ string typeSig(T)() if(canDBus!T) {
     return "d";
   } else static if(is(T == string)) {
     return "s";
-  } else static if(is(T == void)) {
+  } else static if(isVariant!T) {
-    return "";
+    return "v";
   } else static if(isTuple!T) {
     string sig = "(";
     foreach(i, S; T.Types) {
@@ -105,11 +125,13 @@ unittest {
   typeSig!int().assertEqual("i");
   typeSig!bool().assertEqual("b");
   typeSig!string().assertEqual("s");
+  typeSig!(Variant!int)().assertEqual("v");
   // structs
   typeSig!(Tuple!(int,string,string)).assertEqual("(iss)");
-  typeSig!(Tuple!(int,string,Tuple!(int,"k",double,"x"))).assertEqual("(is(id))");
+  typeSig!(Tuple!(int,string,Variant!int,Tuple!(int,"k",double,"x"))).assertEqual("(isv(id))");
   // arrays
   typeSig!(int[]).assertEqual("ai");
+  typeSig!(Variant!int[]).assertEqual("av");
   typeSig!(Tuple!(byte)[][]).assertEqual("aa(y)");
   // multiple arguments
   typeSigAll!(int,bool).assertEqual("ib");