Handle nulls.Int Unmarshal errors properly (#349)

* Handle nulls.Int Unmarshal errors properly

Fixes #341

* Add tests for nulls.Int UnmarshalJSON

nulls/int.go

@@ -57,10 +57,18 @@ func (ns Int) MarshalJSON() ([]byte, error) {
 // UnmarshalJSON will unmarshal a JSON value into
 // the propert representation of that value.
 func (ns *Int) UnmarshalJSON(text []byte) error {
-	if i, err := strconv.ParseInt(string(text), 10, strconv.IntSize); err == nil {
-		ns.Valid = true
-		ns.Int = int(i)
+	txt := string(text)
+	ns.Valid = true
+	if txt == "null" {
+		ns.Valid = false
+		return nil
+	}
+	i, err := strconv.ParseInt(txt, 10, strconv.IntSize)
+	if err != nil {
+		ns.Valid = false
+		return err
 	}
+	ns.Int = int(i)
 	return nil
 }
 

nulls/int_test.go

@@ -0,0 +1,62 @@
+package nulls_test
+
+import (
+	"testing"
+
+	"github.com/gobuffalo/pop/nulls"
+	"github.com/stretchr/testify/require"
+)
+
+func Test_IntUnmarshalJSON(t *testing.T) {
+	r := require.New(t)
+	cases := []struct {
+		Input []byte
+		Value int
+		Valid bool
+	}{
+		{
+			Input: []byte{'0'},
+			Value: 0,
+			Valid: true,
+		},
+		{
+			Input: []byte{'4', '2'},
+			Value: 42,
+			Valid: true,
+		},
+		{
+			Input: []byte{'n', 'u', 'l', 'l'},
+			Value: 0,
+			Valid: false,
+		},
+	}
+
+	for _, c := range cases {
+		i := nulls.Int{}
+		r.NoError(i.UnmarshalJSON(c.Input))
+		r.Equal(c.Value, i.Int)
+		r.Equal(c.Valid, i.Valid)
+	}
+}
+
+func Test_IntUnmarshalJSON_Errors(t *testing.T) {
+	r := require.New(t)
+
+	cases := []struct {
+		Input []byte
+	}{
+		{
+			Input: []byte{'a'},
+		},
+		{
+			Input: []byte{},
+		},
+	}
+
+	for _, c := range cases {
+		i := nulls.Int{}
+		r.Error(i.UnmarshalJSON(c.Input))
+		r.Equal(0, i.Int)
+		r.False(i.Valid)
+	}
+}