From 34a9eba03a2b0809e3226f93b8d2ca11c833afe3 Mon Sep 17 00:00:00 2001
From: NiseVoid <nisevoid@gmail.com>
Date: Tue, 8 Oct 2019 11:09:07 +0200
Subject: [PATCH] Return parse errors

---
 forms.go      | 62 ++++++++++++++++++++++++++++++++++++++-------------
 forms_test.go | 18 ++++++++++++++-
 2 files changed, 64 insertions(+), 16 deletions(-)

diff --git a/forms.go b/forms.go
index bcf3b48..7a555c0 100644
--- a/forms.go
+++ b/forms.go
@@ -8,18 +8,28 @@ import (
 	"unicode"
 )
 
+type DecodeError struct {
+	Field string
+	Type  string
+	Value string
+}
+
+func (de DecodeError) Error() string {
+	return `Failed to decode "` + de.Value + `" into field ` + de.Field + ` of type ` + de.Type + `.`
+}
+
 type Values = map[string][]string
 
-func Decode(form Values, v interface{}) {
+func Decode(form Values, v interface{}) error {
 	rv := reflect.ValueOf(v)
 	if rv.Kind() != reflect.Ptr {
 		panic(`Input is not a pointer`)
 	}
 
-	decode(form, rv.Elem(), ``)
+	return decode(form, rv.Elem(), ``)
 }
 
-func decode(form Values, rv reflect.Value, prefix string) {
+func decode(form Values, rv reflect.Value, prefix string) error {
 	for i := 0; i < rv.NumField(); i++ {
 		ft, fv := rv.Type().Field(i), rv.Field(i)
 
@@ -60,11 +70,15 @@ func decode(form Values, rv reflect.Value, prefix string) {
 				fv = fv.Elem()
 			}
 
-			decode(form, fv, getPrefix(ft, prefix))
+			err := decode(form, fv, getPrefix(ft, prefix))
+			if err != nil {
+				return err
+			}
 			continue
 		}
 
-		v, ok := form[getName(ft, prefix)]
+		fieldName := getName(ft, prefix)
+		v, ok := form[fieldName]
 		if !ok || len(v) == 0 {
 			continue
 		}
@@ -75,37 +89,55 @@ func decode(form Values, rv reflect.Value, prefix string) {
 			fv.Set(reflect.New(ft.Type.Elem()))
 		}
 
-		setValue(v, fv)
+		err := setValue(fieldName, v, fv)
+		if err != nil {
+			return err
+		}
 	}
+
+	return nil
 }
 
-func setValue(values []string, fv reflect.Value) {
+func setValue(fieldName string, values []string, fv reflect.Value) error {
 	if fv.Elem().Type().Kind() != reflect.Slice {
-		parse(values[0], fv)
-		return
+		return parse(fieldName, values[0], fv)
 	}
 
 	slice := reflect.MakeSlice(fv.Elem().Type(), len(values), len(values))
 	val := reflect.New(slice.Type().Elem())
 	for i, v := range values {
-		parse(v, val)
+		err := parse(fieldName, v, val)
+		if err != nil {
+			return err
+		}
 		slice.Index(i).Set(val.Elem())
 	}
 	fv.Elem().Set(slice)
+
+	return nil
 }
 
-func parse(v string, fv reflect.Value) {
+func parse(fieldName, v string, fv reflect.Value) error {
+	var err error
+
 	switch f := fv.Interface().(type) {
 	case *string:
 		*f = v
 	case *int:
-		*f, _ = strconv.Atoi(v)
+		*f, err = strconv.Atoi(v)
 	case *float32:
-		v, _ := strconv.ParseFloat(v, 32)
-		*f = float32(v)
+		var f64 float64
+		f64, err = strconv.ParseFloat(v, 32)
+		*f = float32(f64)
 	case *float64:
-		*f, _ = strconv.ParseFloat(v, 64)
+		*f, err = strconv.ParseFloat(v, 64)
 	}
+
+	if err != nil {
+		return DecodeError{fieldName, fv.Elem().Type().Kind().String(), v}
+	}
+
+	return nil
 }
 
 func getPrefix(ft reflect.StructField, prefix string) string {
diff --git a/forms_test.go b/forms_test.go
index c33ed33..b8cb3dc 100644
--- a/forms_test.go
+++ b/forms_test.go
@@ -73,7 +73,7 @@ var expectedPD = nested{`test5`, 30, 3.75}
 func TestDecode(t *testing.T) {
 	data := testStruct{}
 
-	Decode(input, &data)
+	_ = Decode(input, &data)
 
 	if *data.PA != expectedPA {
 		t.Errorf(`PA was incorrect. Expected %v but got %v`, expectedPA, *data.PA)
@@ -87,3 +87,19 @@ func TestDecode(t *testing.T) {
 		t.Errorf("Data dit not match expected output. Expected \n%v\nbut got\n%v", expected, data)
 	}
 }
+
+func TestDecodeError(t *testing.T) {
+	var data struct {
+		A struct {
+			B float64
+		}
+	}
+
+	err := Decode(Values{`A.B`: {`a`}}, &data)
+
+	if err == nil {
+		t.Error(`Expected error but got nil`)
+	}
+
+	t.Log(err)
+}