fixedn: always correctly unmarshal Fixed8 values

Quoted or not, they should be unmarshalled without going through float64.

pkg/encoding/fixedn/fixed8.go

@@ -1,7 +1,6 @@
 package fixedn
 
 import (
-	"encoding/json"
 	"errors"
 	"strconv"
 	"strings"
@@ -80,34 +79,30 @@ func Fixed8FromString(s string) (Fixed8, error) {
 
 // UnmarshalJSON implements the json unmarshaller interface.
 func (f *Fixed8) UnmarshalJSON(data []byte) error {
-	return f.unmarshalHelper(func(v interface{}) error {
-		return json.Unmarshal(data, v)
-	})
+	if len(data) > 2 {
+		if data[0] == '"' && data[len(data)-1] == '"' {
+			data = data[1 : len(data)-1]
+		}
+	}
+	return f.setFromString(string(data))
 }
 
 // UnmarshalYAML implements the yaml unmarshaler interface.
 func (f *Fixed8) UnmarshalYAML(unmarshal func(interface{}) error) error {
-	return f.unmarshalHelper(unmarshal)
-}
-
-// unmarshalHelper is an underlying unmarshaller func for JSON and YAML.
-func (f *Fixed8) unmarshalHelper(unmarshal func(interface{}) error) error {
 	var s string
-	if err := unmarshal(&s); err == nil {
-		p, err := Fixed8FromString(s)
-		if err != nil {
-			return err
-		}
-		*f = p
-		return nil
-	}
-
-	var fl float64
-	if err := unmarshal(&fl); err != nil {
+	err := unmarshal(&s)
+	if err != nil {
 		return err
 	}
+	return f.setFromString(s)
+}
 
-	*f = Fixed8(decimals * fl)
+func (f *Fixed8) setFromString(s string) error {
+	p, err := Fixed8FromString(s)
+	if err != nil {
+		return err
+	}
+	*f = p
 	return nil
 }
 

pkg/encoding/fixedn/fixed8_test.go

@@ -123,6 +123,19 @@ func TestFixed8UnmarshalJSON(t *testing.T) {
 	}
 }
 
+func TestFixed8_Unmarshal(t *testing.T) {
+	var expected = Fixed8(223719420)
+	var cases = []string{"2.2371942", `"2.2371942"`} // this easily gives 223719419 if interpreted as float
+
+	for _, c := range cases {
+		var u1, u2 Fixed8
+		assert.Nil(t, json.Unmarshal([]byte(c), &u1))
+		assert.Equal(t, expected, u1)
+		assert.Nil(t, yaml.Unmarshal([]byte(c), &u2))
+		assert.Equal(t, expected, u2)
+	}
+}
+
 func TestFixed8_MarshalJSON(t *testing.T) {
 	u, err := Fixed8FromString("123.4")
 	assert.NoError(t, err)