allow optional marshalling JSON without quotes

decimal.go

@@ -43,6 +43,14 @@ import (
 //
 var DivisionPrecision = 16
 
+// Set this to true if you want the decimal to be JSON marshaled as a number,
+// instead of as a string.
+// WARNING: this is dangerous for decimals with many digits, since many JSON
+// unmarshallers (ex: Javascript's) will unmarshal JSON numbers to IEEE 754
+// double-precision floating point numbers, which means you can potentially
+// silently lose precision.
+var MarshalJSONWithoutQuotes = false
+
 // Zero constant, to make computations faster.
 var Zero = New(0, 1)
 
@@ -476,7 +484,12 @@ func (d *Decimal) UnmarshalJSON(decimalBytes []byte) error {
 
 // MarshalJSON implements the json.Marshaler interface.
 func (d Decimal) MarshalJSON() ([]byte, error) {
-	str := "\"" + d.String() + "\""
+	var str string
+	if MarshalJSONWithoutQuotes {
+		str = d.String()
+	} else {
+		str = "\"" + d.String() + "\""
+	}
 	return []byte(str), nil
 }
 

decimal_test.go

@@ -206,6 +206,7 @@ func TestJSON(t *testing.T) {
 			Amount Decimal `json:"amount"`
 		}
 		docStr := `{"amount":"` + s + `"}`
+		docStrNumber := `{"amount":` + s + `}`
 		err := json.Unmarshal([]byte(docStr), &doc)
 		if err != nil {
 			t.Errorf("error unmarshaling %s: %v", docStr, err)
@@ -221,6 +222,16 @@ func TestJSON(t *testing.T) {
 		} else if string(out) != docStr {
 			t.Errorf("expected %s, got %s", docStr, string(out))
 		}
+
+		// make sure unquoted marshalling works too
+		MarshalJSONWithoutQuotes = true
+		out, err = json.Marshal(&doc)
+		if err != nil {
+			t.Errorf("error marshaling %+v: %v", doc, err)
+		} else if string(out) != docStrNumber {
+			t.Errorf("expected %s, got %s", docStrNumber, string(out))
+		}
+		MarshalJSONWithoutQuotes = false
 	}
 }