Whiskers: Support conditional value parameters for lists

libsolutil/Whiskers.cpp

@@ -189,11 +189,13 @@ string Whiskers::replace(
 			if (conditionName[0] == '+')
 			{
 				string tag = conditionName.substr(1);
-				assertThrow(
-					_parameters.count(tag),
-					WhiskersError, "Tag " + tag + " used as condition but was not set."
-				);
-				conditionValue = !_parameters.at(tag).empty();
+
+				if (_parameters.count(tag))
+					conditionValue = !_parameters.at(tag).empty();
+				else if (_listParameters.count(tag))
+					conditionValue = !_listParameters.at(tag).empty();
+				else
+					assertThrow(false, WhiskersError, "Tag " + tag + " used as condition but was not set.");
 			}
 			else
 			{

libsolutil/Whiskers.h

@@ -60,12 +60,13 @@ DEV_SIMPLE_EXCEPTION(WhiskersError);
  *  - Condition parameter: <?name>...<!name>...</name>, where "<!name>" is optional
  *    replaced (and recursively expanded) by the first part if the condition is true
  *    and by the second (or empty string if missing) if the condition is false
- *  - Conditional string parameter: <?+name>...<!+name>...</+name>
- *    Works similar to a conditional parameter where the checked condition is
- *    that the regular (string) parameter called "name" is non-empty.
  *  - List parameter: <#list>...</list>
  *    The part between the tags is repeated as often as values are provided
  *    in the mapping. Each list element can have its own parameter -> value mapping.
+ *  - Conditional value parameter: <?+name>...<!+name>...</+name>
+ *    Works similar to a conditional parameter where the checked condition is
+ *    that the string or list parameter called "name" is non-empty or contains
+ *    no elements respectively.
  */
 class Whiskers
 {