fix default variables

rocktest/rocktest/scenario/contextGetter.go

@@ -1,6 +1,11 @@
 package scenario
 
-import "os"
+import (
+	"os"
+	"regexp"
+
+	log "github.com/sirupsen/logrus"
+)
 
 type ContextGetter struct {
 	scenario *Scenario
@@ -14,18 +19,58 @@ func NewContextGetter(s *Scenario) *ContextGetter {
 
 func (x ContextGetter) Lookup(s string) (string, bool, error) {
 
-	ret, found := x.scenario.GetContext(s)
+	// Do we have expression like
+	// ${variable?value if set::value if not set} or
+	// ${variable::value if not set}
+
+	re, err := regexp.Compile(`([^?]+)(?:\?(.*))?::(.*)`)
+
+	if err != nil {
+		log.Errorf(err.Error())
+		return s, false, nil
+	}
+
+	if re.Match([]byte(s)) {
+		res := re.FindAllStringSubmatch(s, -1)
+
+		name := res[0][1]
+		valset := res[0][2]
+		valunset := res[0][3]
+
+		log.Tracef("%v", res)
+		log.Tracef("Name: \"%s\", Val is set: \"%s\", val if not set: \"%s\"", name, valset, valunset)
 
-	if !found {
-		env := os.Getenv(s)
-		if env == "" {
-			return s, false, nil
+		val, found := x.scenario.GetContext(name)
+
+		if found {
+			if valset != "" {
+				return valset, true, nil
+			} else {
+				return val, true, nil
+			}
 		} else {
-			return env, true, nil
+			if valunset != "" {
+				return valunset, true, nil
+			} else {
+				return s, false, nil
+			}
 		}
 
 	} else {
-		return ret, found, nil
+
+		ret, found := x.scenario.GetContext(s)
+
+		if !found {
+			env := os.Getenv(s)
+			if env == "" {
+				return s, false, nil
+			} else {
+				return env, true, nil
+			}
+
+		} else {
+			return ret, found, nil
+		}
 	}
 
 }