Adds sanity checks for values of --traffic flags

- percent value should range between 0-100
- repetition of revision reference in --traffic flag is not allowed

pkg/kn/traffic/compute.go

@@ -197,9 +197,14 @@ func errorOverWritingTag(tag string) error {
 		"add flag '--untag %s' in command to untag it", tag)
 }
 
-func errorRepeatingLatestRevision(forFlag string) error {
-	return fmt.Errorf("repetition of identifier %s "+
-		"is not allowed, use only once with %s flag", latestRevisionRef, forFlag)
+func errorRepeatingRevision(forFlag string, name string) error {
+	if name == latestRevisionRef {
+		name = "identifier " + latestRevisionRef
+	} else {
+		name = "revision reference " + name
+	}
+	return fmt.Errorf("repetition of %s "+
+		"is not allowed, use only once with %s flag", name, forFlag)
 }
 
 // verifies if user has repeated @latest field in --tag or --traffic flags
@@ -208,7 +213,6 @@ func errorRepeatingLatestRevision(forFlag string) error {
 // - if provided traffic portion are integers
 func verifyInputSanity(trafficFlags *flags.Traffic) error {
 	var latestRevisionTag = false
-	var latestRevisionTraffic = false
 	var sum = 0
 
 	for _, each := range trafficFlags.RevisionsTags {
@@ -218,32 +222,35 @@ func verifyInputSanity(trafficFlags *flags.Traffic) error {
 		}
 
 		if latestRevisionTag && revision == latestRevisionRef {
-			return errorRepeatingLatestRevision("--tag")
-
+			return errorRepeatingRevision("--tag", latestRevisionRef)
 		}
 
 		if revision == latestRevisionRef {
 			latestRevisionTag = true
 		}
 	}
 
-	for _, each := range trafficFlags.RevisionsPercentages {
+	revisionRefMap := make(map[string]int)
+	for i, each := range trafficFlags.RevisionsPercentages {
 		revisionRef, percent, err := splitByEqualSign(each)
 		if err != nil {
 			return err
 		}
 
+		// To check if there are duplicate revision names in traffic flags
+		if _, exist := revisionRefMap[revisionRef]; exist {
+			return errorRepeatingRevision("--traffic", revisionRef)
+		} else {
+			revisionRefMap[revisionRef] = i
+		}
+
 		percentInt, err := strconv.Atoi(percent)
 		if err != nil {
 			return fmt.Errorf("error converting given %s to integer value for traffic distribution", percent)
 		}
 
-		if latestRevisionTraffic && revisionRef == latestRevisionRef {
-			return errorRepeatingLatestRevision("--traffic")
-		}
-
-		if revisionRef == latestRevisionRef {
-			latestRevisionTraffic = true
+		if percentInt < 0 || percentInt > 100 {
+			return fmt.Errorf("invalid value for traffic percent %d, expected 0 <= percent <= 100", percentInt)
 		}
 
 		sum += percentInt

pkg/kn/traffic/compute_test.go

@@ -265,6 +265,18 @@ func TestComputeErrMsg(t *testing.T) {
 			[]string{"--traffic", "@latest=19,echo-v1=71"},
 			"given traffic percents sum to 90, want 100",
 		},
+		{
+			"verify error for values out of range given to percent",
+			append(newServiceTraffic([]v1alpha1.TrafficTarget{}), newTarget("", "", 100, true)),
+			[]string{"--traffic", "@latest=-100"},
+			"invalid value for traffic percent -100, expected 0 <= percent <= 100",
+		},
+		{
+			"repeatedly spliting traffic to the same revision",
+			append(newServiceTraffic([]v1alpha1.TrafficTarget{}), newTarget("", "", 100, true)),
+			[]string{"--traffic", "echo-v1=40", "--traffic", "echo-v1=60"},
+			"repetition of revision reference echo-v1 is not allowed, use only once with --traffic flag",
+		},
 	} {
 		t.Run(testCase.name, func(t *testing.T) {
 			testCmd, tFlags := newTestTrafficCommand()