Merge pull request #837 from AleksandrMatsko/fix/runtime-error-highes…

…t-current

fix: runtime error highest current

expr/functions/highestLowest/function.go

@@ -45,8 +45,6 @@ func (f *highest) Do(ctx context.Context, eval interfaces.Evaluator, e parser.Ex
 		}
 	}
 
-	var results []*types.MetricData
-
 	// we have fewer arguments than we want result series
 	if len(arg) < n {
 		return arg, nil
@@ -100,6 +98,12 @@ func (f *highest) Do(ctx context.Context, eval interfaces.Evaluator, e parser.Ex
 		return nil, fmt.Errorf("unsupported function %v", e.Target())
 	}
 
+	var results []*types.MetricData
+
+	if n <= 0 {
+		return results, nil
+	}
+
 	if isHighest {
 		for i, a := range arg {
 			m := compute(a.Values)

expr/functions/highestLowest/function_test.go

@@ -231,6 +231,17 @@ func TestHighest(t *testing.T) {
 			[]*types.MetricData{types.MakeMetricData("metricB", // NOTE(dgryski): not sure if this matches graphite
 				[]float64{2, 5, 5, 5, 5, 5}, 1, now32)},
 		},
+		{
+			"highestCurrent(metric1,0)",
+			map[parser.MetricRequest][]*types.MetricData{
+				parser.MetricRequest{Metric: "metric1", From: 0, Until: 1}: {
+					types.MakeMetricData("metricA", []float64{1, 1, 3, 3, 4, 12}, 1, now32),
+					types.MakeMetricData("metricB", []float64{1, 1, 3, 3, 4, 1}, 1, now32),
+					types.MakeMetricData("metricC", []float64{1, 1, 3, 3, 4, 15}, 1, now32),
+				},
+			},
+			[]*types.MetricData{},
+		},
 		{
 			"highest(metric1,\"max\")",
 			map[parser.MetricRequest][]*types.MetricData{
@@ -243,6 +254,28 @@ func TestHighest(t *testing.T) {
 			[]*types.MetricData{types.MakeMetricData("metricA",
 				[]float64{1, 1, 3, 3, 12, 11}, 1, now32)},
 		},
+		{
+			"highest(metric1, 0, \"max\")",
+			map[parser.MetricRequest][]*types.MetricData{
+				{Metric: "metric1", From: 0, Until: 1}: {
+					types.MakeMetricData("metricA", []float64{1, 1, 3, 3, 12, 11}, 1, now32),
+					types.MakeMetricData("metricB", []float64{1, 1, 3, 3, 4, 1}, 1, now32),
+					types.MakeMetricData("metricC", []float64{1, 1, 3, 3, 4, 10}, 1, now32),
+				},
+			},
+			[]*types.MetricData{},
+		},
+		{
+			"highest(metric1, -1, \"max\")",
+			map[parser.MetricRequest][]*types.MetricData{
+				{Metric: "metric1", From: 0, Until: 1}: {
+					types.MakeMetricData("metricA", []float64{1, 1, 3, 3, 12, 11}, 1, now32),
+					types.MakeMetricData("metricB", []float64{1, 1, 3, 3, 4, 1}, 1, now32),
+					types.MakeMetricData("metricC", []float64{1, 1, 3, 3, 4, 10}, 1, now32),
+				},
+			},
+			[]*types.MetricData{},
+		},
 		{
 			"lowest(metric1,\"max\")",
 			map[parser.MetricRequest][]*types.MetricData{