option to disable UnmarshalText interface

formam.go

@@ -81,6 +81,9 @@ type DecoderOptions struct {
 	// Prefer UnmarshalText over custom types.
 	PrefUnmarshalText bool
 
+	// Disable UnmarshalText interface
+	DisableUnmarshalText bool
+
 	// Ignore unknown form fields. By default unknown fields are an error
 	// (although all valid keys will still be decoded).
 	IgnoreUnknownKeys bool
@@ -371,20 +374,27 @@ func (dec *Decoder) traverseInMap(byField bool) {
 
 // decode sets the value in the field
 func (dec *Decoder) decode() error {
-	// check if has UnmarshalText method or a custom function to decode it
-	if dec.opts.PrefUnmarshalText {
-		if ok, err := dec.isUnmarshalText(dec.curr); ok || err != nil {
-			return err
-		}
+	// if DisableUnmarshalText is true then only use customType if available
+	if dec.opts.DisableUnmarshalText {
 		if ok, err := dec.isCustomType(); ok || err != nil {
 			return err
 		}
 	} else {
-		if ok, err := dec.isCustomType(); ok || err != nil {
-			return err
-		}
-		if ok, err := dec.isUnmarshalText(dec.curr); ok || err != nil {
-			return err
+		// check if has UnmarshalText method or a custom function to decode it
+		if dec.opts.PrefUnmarshalText {
+			if ok, err := dec.isUnmarshalText(dec.curr); ok || err != nil {
+				return err
+			}
+			if ok, err := dec.isCustomType(); ok || err != nil {
+				return err
+			}
+		} else {
+			if ok, err := dec.isCustomType(); ok || err != nil {
+				return err
+			}
+			if ok, err := dec.isUnmarshalText(dec.curr); ok || err != nil {
+				return err
+			}
 		}
 	}
 
@@ -654,6 +664,8 @@ var (
 
 // isUnmarshalText returns a boolean and error. The boolean is true if the
 // field's type implements TextUnmarshaler, and false if not.
+// If the field implements TextUnmarshaler, then it is used to decode the value
+// in the field.
 func (dec *Decoder) isUnmarshalText(v reflect.Value) (bool, error) {
 	// check if implements the interface
 	m, ok := v.Interface().(encoding.TextUnmarshaler)

formam_test.go

@@ -971,6 +971,47 @@ func TestArrayLength(t *testing.T) {
 	}
 }
 
+type StringWithUnmarshalText string
+
+func (s *StringWithUnmarshalText) UnmarshalText(data []byte) error {
+	*s = "string by UnmarshalText"
+	return nil
+}
+
+func TestEnableUnmarshalText(t *testing.T) {
+	s := struct {
+		Text StringWithUnmarshalText
+	}{}
+	vals := url.Values{
+		"Text": []string{"string by form"},
+	}
+	dec := formam.NewDecoder(&formam.DecoderOptions{})
+	if err := dec.Decode(vals, &s); err != nil {
+		t.Fatalf("error when decode %s", err)
+	}
+	if s.Text != "string by UnmarshalText" {
+		t.Errorf("the UnmarshalText hasn't been called")
+	}
+}
+
+func TestDisableUnmarshalText(t *testing.T) {
+	s := struct {
+		Text StringWithUnmarshalText
+	}{}
+	vals := url.Values{
+		"Text": []string{"string by form"},
+	}
+	dec := formam.NewDecoder(&formam.DecoderOptions{
+		DisableUnmarshalText: true,
+	})
+	if err := dec.Decode(vals, &s); err != nil {
+		t.Fatalf("error when decode %s", err)
+	}
+	if s.Text != "string by form" {
+		t.Errorf("the UnmarshalText has been called")
+	}
+}
+
 // errorContains checks if the error message in out contains the text in
 // want.
 //