util: json: Allow converting a virTristate(Bool|Switch) into JSON

Add a new modifier letter for virJSONValueObjectAddVArgs which will add
a boolean value with our tristate semantics. The value is omitted when
the _ABSENT value is used.
Signed-off-by: NPeter Krempa <pkrempa@redhat.com>
Reviewed-by: NErik Skultety <eskultet@redhat.com>

src/util/virjson.c

@@ -142,6 +142,8 @@ virJSONValueGetType(const virJSONValue *value)
  *
  * b: boolean value
  * B: boolean value, omitted if false
+ * T: boolean value specified by a virTristate(Bool|Switch) value, omitted on
+ * the _ABSENT value
  *
  * d: double precision floating point number
  * n: json null value
@@ -265,6 +267,7 @@ virJSONValueObjectAddVArgs(virJSONValuePtr obj,
             rc = virJSONValueObjectAppendNumberDouble(obj, key, val);
         }   break;
 
+        case 'T':
         case 'B':
         case 'b': {
             int val = va_arg(args, int);
@@ -272,6 +275,16 @@ virJSONValueObjectAddVArgs(virJSONValuePtr obj,
             if (!val && type == 'B')
                 continue;
 
+            if (type == 'T') {
+                if (val == VIR_TRISTATE_BOOL_ABSENT)
+                    continue;
+
+                if (val == VIR_TRISTATE_BOOL_NO)
+                    val = 0;
+                else
+                    val = 1;
+            }
+
             rc = virJSONValueObjectAppendBoolean(obj, key, val);
         }   break;