✨ Add AddFormatter function to allow custom builds to register new formatters

formatters/json.go

@@ -10,6 +10,8 @@ import (
 	"github.com/spf13/viper"
 )
 
+const FormatJSON string = "json"
+
 func newJson(ff *viper.Viper) (Formatter, error) {
 	js := new(Json)
 	err := ff.Unmarshal(js)
@@ -24,7 +26,7 @@ type Json struct {
 }
 
 func (js *Json) Name() string {
-	return "json"
+	return FormatJSON
 }
 
 func (js *Json) marshal(v any) (o []byte, err error) {

formatters/new.go

@@ -2,18 +2,22 @@ package formatters
 
 import (
 	"context"
+	"errors"
 	"fmt"
+	"sync"
 
 	"codeberg.org/danjones000/my-log/config"
 	"github.com/spf13/viper"
 )
 
-type formatMaker func(config *viper.Viper) (Formatter, error)
+var mut sync.RWMutex
 
-var formatterMap = map[string]formatMaker{
-	"plain": newPlain,
-	"json":  newJson,
-	"zero":  newNull,
+type FormatInit func(config *viper.Viper) (Formatter, error)
+
+var formatterMap = map[string]FormatInit{
+	FormatPlain: newPlain,
+	FormatJSON:  newJson,
+	FormatNull:  newNull,
 }
 
 func Preferred(ctx context.Context) (f Formatter, err error) {
@@ -25,6 +29,8 @@ func New(ctx context.Context, kind string) (f Formatter, err error) {
 	v, _ := config.RetrieveFromContext(ctx)
 	formatterConf := v.Sub("formatters." + kind)
 
+	mut.RLock()
+	defer mut.RUnlock()
 	if maker, ok := formatterMap[kind]; ok {
 		return maker(formatterConf)
 	}
@@ -34,8 +40,24 @@ func New(ctx context.Context, kind string) (f Formatter, err error) {
 
 func Kinds() []string {
 	r := []string{}
+
+	mut.RLock()
+	defer mut.RUnlock()
 	for kind, _ := range formatterMap {
 		r = append(r, kind)
 	}
 	return r
 }
+
+var ErrAlreadyAdded = errors.New("formatter already present")
+
+func AddFormatter(key string, f FormatInit) error {
+	mut.Lock()
+	defer mut.Unlock()
+	if _, present := formatterMap[key]; present {
+		return fmt.Errorf("%w: %s", ErrAlreadyAdded, key)
+	}
+
+	formatterMap[key] = f
+	return nil
+}

formatters/new_test.go

@@ -39,3 +39,17 @@ func TestPreferred(t *testing.T) {
 	be.Err(t, err, nil)
 	be.True(t, form != nil)
 }
+
+type dummyFormatter struct{ Null }
+
+func (dummyFormatter) Name() string { return "dummy" }
+
+func TestAddFormatter(t *testing.T) {
+	var df dummyFormatter
+	dummyInit := func(*viper.Viper) (Formatter, error) { return df, nil }
+	err := AddFormatter(df.Name(), dummyInit)
+	be.Err(t, err, nil)
+
+	err = AddFormatter(df.Name(), dummyInit)
+	be.Err(t, err, ErrAlreadyAdded)
+}

formatters/null.go

@@ -5,28 +5,19 @@ import (
 	"github.com/spf13/viper"
 )
 
-func newNull(ff *viper.Viper) (Formatter, error) {
-	return &Null{}, nil
+const FormatNull = "zero"
+
+func newNull(*viper.Viper) (Formatter, error) {
+	return Null{}, nil
 }
 
 type Null struct{}
 
-func (n *Null) Name() string {
-	return "zero"
+func (Null) Name() string {
+	return FormatNull
 }
 
-func (n *Null) Meta(m models.Meta) (o []byte, err error) {
-	return
-}
-
-func (n *Null) Entry(e models.Entry) (o []byte, err error) {
-	return
-}
-
-func (n *Null) Log(l models.Log) (o []byte, err error) {
-	return
-}
-
-func (n *Null) Logs(logs []models.Log) (out []byte, err error) {
-	return
-}
+func (Null) Meta(m models.Meta) (o []byte, err error)       { return }
+func (Null) Entry(e models.Entry) (o []byte, err error)     { return }
+func (Null) Log(l models.Log) (o []byte, err error)         { return }
+func (Null) Logs(logs []models.Log) (out []byte, err error) { return }

formatters/plain.go

@@ -8,16 +8,16 @@ import (
 	"github.com/spf13/viper"
 )
 
-func newPlain(ff *viper.Viper) (Formatter, error) {
+const FormatPlain string = "plain"
+
+func newPlain(*viper.Viper) (Formatter, error) {
 	return &PlainText{}, nil
 }
 
-type PlainText struct {
-	// config might go here some day
-}
+type PlainText struct{}
 
-func (pt *PlainText) Name() string {
-	return "plain"
+func (*PlainText) Name() string {
+	return FormatPlain
 }
 
 func (pt *PlainText) Logs(logs []models.Log) (out []byte, err error) {