TW-1607: Theme Support for missing UDAs

- Thanks to Stefan Betz.

ChangeLog

@@ -78,6 +78,7 @@
           if a context is active (thanks to Johannes Schlatow).
 - TW-1600 Filtering "regressions"(?) in task-2.4.3, task-2.4.4 (thanks to Ralph
           Bean).
+- TW-1607 Theme Support for missing UDAs (thanks to Stefan Betz).
 - TW-1609 In 'urgency<10', 10 is interpreted as an ID (thanks to Wim Schuermann).
 - TW-1611 soww weirdness (thanks to Wim Schuermann).
 - TW-1612 Spurious whitespace added in task descriptions around certain symbols

NEWS

@@ -17,6 +17,8 @@ New configuration options in Taskwarrior 2.4.5
   - The 'json.depends.array' setting controls whether dependencies are exported
     as a JSON array, of a comma-separated string.  Default is 'on'.
     Both variations are imported.
+  - The 'color.uda.<name>.none' is a color that is applieѕ to tasks that do
+    not have a value for the UDA '<name>'.
 
 Newly deprecated features in Taskwarrior 2.4.5
 

doc/man/taskrc.5.in

@@ -911,6 +911,11 @@ Colors any task that has the user defined attribute X.
 Colors any task that has the user defined attribute X set to VALUE.
 .RE
 
+.TP
+.B color.uda.X.none=on green
+Colors any task that does not have the user defined attribute X.
+.RE
+
 .TP
 .B color.error=green
 Colors any of the error messages.

src/rules.cpp

@@ -197,7 +197,7 @@ static void colorizeKeyword (Task& task, const std::string& rule, const Color& b
 ////////////////////////////////////////////////////////////////////////////////
 static void colorizeUDA (Task& task, const std::string& rule, const Color& base, Color& c)
 {
-  // Is the rule uda.name.value or uda.name?
+  // Is the rule color.uda.name.value or color.uda.name?
   size_t pos = rule.find (".", 10);
   if (pos == std::string::npos)
   {
@@ -208,7 +208,9 @@ static void colorizeUDA (Task& task, const std::string& rule, const Color& base,
   {
     const std::string uda = rule.substr (10, pos - 10);
     const std::string val = rule.substr (pos + 1);
-    if (task.get (uda) == val)
+    if (val == "none" && ! task.has (uda))
+      c.blend (base);
+    else if (task.get (uda) == val)
       c.blend (base);
   }
 }