add monkit:ignore tag for structs

struct.go

@@ -14,7 +14,10 @@
 
 package monkit
 
-import "reflect"
+import (
+	"reflect"
+	"strings"
+)
 
 var (
 	f64Type  = reflect.TypeOf(float64(0))
@@ -36,10 +39,18 @@ func StatSourceFromStruct(key SeriesKey, structData interface{}) StatSource {
 	}
 
 	return StatSourceFunc(func(cb func(key SeriesKey, field string, val float64)) {
+	nextField:
 		for i := 0; i < typ.NumField(); i++ {
 			field := deref(val.Field(i))
 			field_type := field.Type()
 
+			parts := strings.Split(typ.Field(i).Tag.Get("monkit"), ",")
+			for _, part := range parts {
+				if part == "ignore" {
+					continue nextField
+				}
+			}
+
 			if field_type.Kind() == reflect.Struct && field.CanInterface() {
 				child_source := StatSourceFromStruct(key, field.Interface())
 				child_source.Stats(func(key SeriesKey, field string, val float64) {

struct_test.go

@@ -0,0 +1,45 @@
+package monkit
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestStatSourceFromStruct(t *testing.T) {
+	type SubStruct struct {
+		SubBool  bool
+		SubFloat float64
+		SubInt   int64
+		Ignored  float64 `monkit:"ignore"`
+	}
+
+	result := Collect(StatSourceFromStruct(NewSeriesKey("struct"),
+		struct {
+			SomeBool  bool
+			SomeFloat float64
+			SomeInt   int64
+			Ignored   float64 `monkit:"ignore"`
+			Sub       SubStruct
+			Skip      struct {
+				Nope int64
+			} `monkit:"whatever,ignore"`
+		}{
+			SomeInt:  5,
+			SomeBool: true,
+			Sub: SubStruct{
+				SubFloat: 3.2,
+			},
+		},
+	))
+
+	if !reflect.DeepEqual(result, map[string]float64{
+		"struct SomeBool":     1,
+		"struct SomeFloat":    0,
+		"struct SomeInt":      5,
+		"struct Sub.SubBool":  0,
+		"struct Sub.SubFloat": 3.2,
+		"struct Sub.SubInt":   0,
+	}) {
+		t.Fatal("unexpected result", result)
+	}
+}