types: Add Int.ZeroToNull, String.EmptyToNull

These two methods were derived from Icinga Notifications utility
functions, mapping an empty string or zero to a NULL value. In order to
integrate this utility functions in the IGL, they were added as builder
methods to types.Int and types.String.

Imported from:
- ToDBInt, Icinga/icinga-notifications@f0b39f0
- ToDBString, Icinga/icinga-notifications@8183344

As a drive-by change, a MakeInt function was added similar to
MakeString. Otherwise, creating types.Int instances from within Icinga
Notifications was a bit ugly.

Co-Authored-By: Yonas Habteab <[email protected]>

Author: oxzi

types/int.go

@@ -14,6 +14,14 @@ type Int struct {
 	sql.NullInt64
 }
 
+// MakeInt constructs a new non-NULL Int from i.
+func MakeInt(i int64) Int {
+	return Int{sql.NullInt64{
+		Int64: i,
+		Valid: true,
+	}}
+}
+
 // MarshalJSON implements the json.Marshaler interface.
 // Supports JSON null.
 func (i Int) MarshalJSON() ([]byte, error) {
@@ -57,6 +65,14 @@ func (i *Int) UnmarshalJSON(data []byte) error {
 	return nil
 }
 
+// ZeroToNull either returns this Int or a NULL Int if the internal int is zero.
+func (i Int) ZeroToNull() Int {
+	if i.Int64 != 0 {
+		return i
+	}
+	return Int{sql.NullInt64{Valid: false}}
+}
+
 // Assert interface compliance.
 var (
 	_ json.Marshaler           = Int{}

types/int_test.go

@@ -85,3 +85,22 @@ func TestInt_UnmarshalJSON(t *testing.T) {
 		})
 	}
 }
+
+func TestInt_ZeroToNull(t *testing.T) {
+	subtests := []struct {
+		name   string
+		input  Int
+		output Int
+	}{
+		{"nil", Int{sql.NullInt64{}}, Int{sql.NullInt64{}}},
+		{"zero", MakeInt(0), Int{sql.NullInt64{Valid: false}}},
+		{"non-zero", MakeInt(1), MakeInt(1)},
+	}
+
+	for _, st := range subtests {
+		t.Run(st.name, func(t *testing.T) {
+			actual := st.input.ZeroToNull()
+			require.Equal(t, st.output, actual)
+		})
+	}
+}

types/string.go

@@ -71,6 +71,14 @@ func (s String) Value() (driver.Value, error) {
 	return strings.ReplaceAll(s.String, "\x00", ""), nil
 }
 
+// EmptyToNull either returns this String or a NULL String if the internal string is empty.
+func (s String) EmptyToNull() String {
+	if s.String != "" {
+		return s
+	}
+	return String{sql.NullString{Valid: false}}
+}
+
 // Assert interface compliance.
 var (
 	_ json.Marshaler           = String{}

types/string_test.go

@@ -124,3 +124,22 @@ func TestString_Value(t *testing.T) {
 		})
 	}
 }
+
+func TestString_EmptyToNull(t *testing.T) {
+	subtests := []struct {
+		name   string
+		input  String
+		output String
+	}{
+		{"nil", String{sql.NullString{}}, String{sql.NullString{}}},
+		{"empty", MakeString(""), String{sql.NullString{Valid: false}}},
+		{"non-empty", MakeString("foo"), String{sql.NullString{String: "foo", Valid: true}}},
+	}
+
+	for _, st := range subtests {
+		t.Run(st.name, func(t *testing.T) {
+			actual := st.input.EmptyToNull()
+			require.Equal(t, st.output, actual)
+		})
+	}
+}