feat: add nullable.Time

time.go

@@ -0,0 +1,31 @@
+package nullable
+
+import (
+	"bytes"
+	"encoding/json"
+	"time"
+)
+
+// Time represents a time that may be null or not
+// present in json at all.
+type Time struct {
+	Present bool // Present is true if key is present in json
+	Valid   bool // Valid is true if value is not null and valid time
+	Value   time.Time
+}
+
+// UnmarshalJSON implements json.Marshaler interface.
+func (t *Time) UnmarshalJSON(data []byte) error {
+	t.Present = true
+
+	if bytes.Equal(data, null) {
+		return nil
+	}
+
+	if err := json.Unmarshal(data, &t.Value); err != nil {
+		return err
+	}
+
+	t.Valid = true
+	return nil
+}

time_test.go

@@ -0,0 +1,68 @@
+package nullable
+
+import (
+	"bytes"
+	"encoding/json"
+	"testing"
+	"time"
+)
+
+var referenceDate = time.Date(1991, 5, 23, 1, 2, 3, 4, time.UTC)
+
+func TestTime_UnmarshalJSON(t *testing.T) {
+	tests := []struct {
+		name      string
+		buf       *bytes.Buffer
+		expect    Time
+		expectErr error
+	}{
+		{
+			name: "null value",
+			buf:  bytes.NewBufferString(`{"value":null}`),
+			expect: Time{
+				Present: true,
+			},
+			expectErr: nil,
+		},
+		{
+			name: "valid value",
+			buf:  bytes.NewBufferString(`{"value":"` + referenceDate.Format(time.RFC3339Nano) + `"}`),
+			expect: Time{
+				Present: true,
+				Valid:   true,
+				Value:   referenceDate,
+			},
+			expectErr: nil,
+		},
+		{
+			name:      "empty",
+			buf:       bytes.NewBufferString(`{}`),
+			expect:    Time{},
+			expectErr: nil,
+		},
+		{
+			name: "unmarshallable",
+			buf:  bytes.NewBufferString(`{"value":42}`),
+			expect: Time{
+				Present: true,
+			},
+			expectErr: &time.ParseError{},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			str := struct {
+				Value Time `json:"value"`
+			}{}
+
+			if err := json.Unmarshal(tt.buf.Bytes(), &str); !typeMatch(tt.expectErr, err) {
+				t.Fatalf("unexpected unmarshaling error: %s", err)
+			}
+
+			got := str.Value
+			if got.Present != tt.expect.Present || got.Valid != tt.expect.Valid || got.Value != tt.expect.Value {
+				t.Errorf("expected value to be %#v got %#v", tt.expect, got)
+			}
+		})
+	}
+}