This fixes an issue with the type switch that was never able to fall (#88)

into cases of []<number>, being <number> a number type such as int,
float32, float64. This is because Go can't type cast slices of
interface{} out right because it's impossible to know the true types of
the slice members beforehand.

Signed-off-by: Tomás Pinho <me@tomaspinho.com>

pkg/collector/json_path_collector.go

@@ -89,17 +89,38 @@ func (g *JSONPathMetricsGetter) GetMetric(pod *corev1.Pod) (float64, error) {
 		return float64(res), nil
 	case float64:
 		return res, nil
-	case []int:
-		return reduce(intsToFloat64s(res), g.aggregator)
-	case []float32:
-		return reduce(float32sToFloat64s(res), g.aggregator)
-	case []float64:
-		return reduce(res, g.aggregator)
+	case []interface{}:
+		s, err := castSlice(res)
+		if err != nil {
+			return 0, err
+		}
+		return reduce(s, g.aggregator)
 	default:
 		return 0, fmt.Errorf("unsupported type %T", res)
 	}
 }
 
+// castSlice takes a slice of interface and returns a slice of float64 if all
+// values in slice were castable, else returns an error
+func castSlice(in []interface{}) ([]float64, error) {
+	out := []float64{}
+
+	for _, v := range in {
+		switch v := v.(type) {
+		case int:
+			out = append(out, float64(v))
+		case float32:
+			out = append(out, float64(v))
+		case float64:
+			out = append(out, v)
+		default:
+			return nil, fmt.Errorf("slice was returned by JSONPath, but value inside is unsupported: %T", v)
+		}
+	}
+
+	return out, nil
+}
+
 // getPodMetrics returns the content of the pods metrics endpoint.
 func getPodMetrics(pod *corev1.Pod, scheme, path string, port int) ([]byte, error) {
 	if pod.Status.PodIP == "" {
@@ -144,24 +165,6 @@ func getPodMetrics(pod *corev1.Pod, scheme, path string, port int) ([]byte, erro
 	return data, nil
 }
 
-// intsToFloat64s will convert a slice of int to a slice of float64
-func intsToFloat64s(in []int) (out []float64) {
-	out = []float64{}
-	for _, v := range in {
-		out = append(out, float64(v))
-	}
-	return
-}
-
-// float32sToFloat64s will convert a slice of float32 to a slice of float64
-func float32sToFloat64s(in []float32) (out []float64) {
-	out = []float64{}
-	for _, v := range in {
-		out = append(out, float64(v))
-	}
-	return
-}
-
 // reduce will reduce a slice of numbers given a aggregator function's name. If it's empty or not recognized, an error is returned.
 func reduce(values []float64, aggregator string) (float64, error) {
 	switch aggregator {

pkg/collector/json_path_collector_test.go

@@ -65,24 +65,22 @@ func TestNewJSONPathMetricsGetter(t *testing.T) {
 	require.Error(t, err4)
 }
 
-func TestIntsToFloat64s(t *testing.T) {
-	noInts := []int{}
-	noFloat64s := intsToFloat64s(noInts)
-	require.Equal(t, []float64{}, noFloat64s)
+func TestCastSlice(t *testing.T) {
+	res1, err1 := castSlice([]interface{}{1, 2, 3})
+	require.NoError(t, err1)
+	require.Equal(t, []float64{1.0, 2.0, 3.0}, res1)
 
-	someInts := []int{1, 2, 3}
-	someFloat64s := intsToFloat64s(someInts)
-	require.Equal(t, []float64{1.0, 2.0, 3.0}, someFloat64s)
-}
+	res2, err2 := castSlice([]interface{}{float32(1.0), float32(2.0), float32(3.0)})
+	require.NoError(t, err2)
+	require.Equal(t, []float64{1.0, 2.0, 3.0}, res2)
 
-func TestFloat32sToFloat64s(t *testing.T) {
-	noFloat32s := []float32{}
-	noFloat64s := float32sToFloat64s(noFloat32s)
-	require.Equal(t, []float64{}, noFloat64s)
+	res3, err3 := castSlice([]interface{}{float64(1.0), float64(2.0), float64(3.0)})
+	require.NoError(t, err3)
+	require.Equal(t, []float64{1.0, 2.0, 3.0}, res3)
 
-	someFloat32s := []float32{1.0, 2.0, 3.0}
-	someFloat64s := float32sToFloat64s(someFloat32s)
-	require.Equal(t, []float64{1.0, 2.0, 3.0}, someFloat64s)
+	res4, err4 := castSlice([]interface{}{1, 2, "some string"})
+	require.Errorf(t, err4, "slice was returned by JSONPath, but value inside is unsupported: %T", "string")
+	require.Equal(t, []float64(nil), res4)
 }
 
 func TestReduce(t *testing.T) {