feat(encoding)!: accept a map in the encoder interface

This interface is specific to encoding data from Viper's internal,
so it's okay to make it Viper specific.

BREAKING CHANGE: the encoder interface now accepts a map instead of an interface

Signed-off-by: Mark Sagi-Kazar <mark.sagikazar@gmail.com>

internal/encoding/encoder.go

@@ -7,7 +7,7 @@ import (
 // Encoder encodes the contents of v into a byte representation.
 // It's primarily used for encoding a map[string]interface{} into a file format.
 type Encoder interface {
-	Encode(v interface{}) ([]byte, error)
+	Encode(v map[string]interface{}) ([]byte, error)
 }
 
 const (
@@ -47,7 +47,7 @@ func (e *EncoderRegistry) RegisterEncoder(format string, enc Encoder) error {
 	return nil
 }
 
-func (e *EncoderRegistry) Encode(format string, v interface{}) ([]byte, error) {
+func (e *EncoderRegistry) Encode(format string, v map[string]interface{}) ([]byte, error) {
 	e.mu.RLock()
 	encoder, ok := e.encoders[format]
 	e.mu.RUnlock()

internal/encoding/encoder_test.go

@@ -8,7 +8,7 @@ type encoder struct {
 	b []byte
 }
 
-func (e encoder) Encode(_ interface{}) ([]byte, error) {
+func (e encoder) Encode(_ map[string]interface{}) ([]byte, error) {
 	return e.b, nil
 }
 
@@ -41,7 +41,7 @@ func TestEncoderRegistry_Decode(t *testing.T) {
 	t.Run("OK", func(t *testing.T) {
 		registry := NewEncoderRegistry()
 		encoder := encoder{
-			b: []byte("encoded value"),
+			b: []byte("key: value"),
 		}
 
 		err := registry.RegisterEncoder("myformat", encoder)
@@ -49,20 +49,20 @@ func TestEncoderRegistry_Decode(t *testing.T) {
 			t.Fatal(err)
 		}
 
-		b, err := registry.Encode("myformat", "some value")
+		b, err := registry.Encode("myformat", map[string]interface{}{"key": "value"})
 		if err != nil {
 			t.Fatal(err)
 		}
 
-		if string(b) != "encoded value" {
-			t.Fatalf("expected 'encoded value', got: %#v", string(b))
+		if string(b) != "key: value" {
+			t.Fatalf("expected 'key: value', got: %#v", string(b))
 		}
 	})
 
 	t.Run("EncoderNotFound", func(t *testing.T) {
 		registry := NewEncoderRegistry()
 
-		_, err := registry.Encode("myformat", "some value")
+		_, err := registry.Encode("myformat", map[string]interface{}{"key": "value"})
 		if err != ErrEncoderNotFound {
 			t.Fatalf("expected ErrEncoderNotFound, got: %v", err)
 		}

internal/encoding/hcl/codec.go

@@ -12,7 +12,7 @@ import (
 // TODO: add printer config to the codec?
 type Codec struct{}
 
-func (Codec) Encode(v interface{}) ([]byte, error) {
+func (Codec) Encode(v map[string]interface{}) ([]byte, error) {
 	b, err := json.Marshal(v)
 	if err != nil {
 		return nil, err

internal/encoding/json/codec.go

@@ -7,7 +7,7 @@ import (
 // Codec implements the encoding.Encoder and encoding.Decoder interfaces for JSON encoding.
 type Codec struct{}
 
-func (Codec) Encode(v interface{}) ([]byte, error) {
+func (Codec) Encode(v map[string]interface{}) ([]byte, error) {
 	// TODO: expose prefix and indent in the Codec as setting?
 	return json.MarshalIndent(v, "", "  ")
 }

internal/encoding/toml/codec.go

@@ -7,22 +7,18 @@ import (
 // Codec implements the encoding.Encoder and encoding.Decoder interfaces for TOML encoding.
 type Codec struct{}
 
-func (Codec) Encode(v interface{}) ([]byte, error) {
-	if m, ok := v.(map[string]interface{}); ok {
-		t, err := toml.TreeFromMap(m)
-		if err != nil {
-			return nil, err
-		}
-
-		s, err := t.ToTomlString()
-		if err != nil {
-			return nil, err
-		}
-
-		return []byte(s), nil
+func (Codec) Encode(v map[string]interface{}) ([]byte, error) {
+	t, err := toml.TreeFromMap(v)
+	if err != nil {
+		return nil, err
 	}
 
-	return toml.Marshal(v)
+	s, err := t.ToTomlString()
+	if err != nil {
+		return nil, err
+	}
+
+	return []byte(s), nil
 }
 
 func (Codec) Decode(b []byte, v map[string]interface{}) error {

internal/encoding/yaml/codec.go

@@ -5,7 +5,7 @@ import "gopkg.in/yaml.v2"
 // Codec implements the encoding.Encoder and encoding.Decoder interfaces for YAML encoding.
 type Codec struct{}
 
-func (Codec) Encode(v interface{}) ([]byte, error) {
+func (Codec) Encode(v map[string]interface{}) ([]byte, error) {
 	return yaml.Marshal(v)
 }