feat: add DerefOrEmpty func to the client

next/deref.go

@@ -0,0 +1,22 @@
+package next
+
+import "reflect"
+
+// DerefOrEmpty returns the dereferenced value of the input pointer, or the zero
+// value of the type if the input is nil.
+func DerefOrEmpty[T any](in *T) T {
+ if in == nil {
+ tType := reflect.TypeOf(*new(T))
+ switch tType.Kind() {
+ case reflect.Slice, reflect.Array:
+ return reflect.MakeSlice(tType, 0, 0).Interface().(T)
+ case reflect.Map:
+ return reflect.MakeMap(tType).Interface().(T)
+ default:
+ var empty T
+ return empty
+ }
+ }
+
+ return *in
+}

next/deref_test.go

@@ -0,0 +1,167 @@
+package next_test
+
+import (
+ "testing"
+
+ "github.com/krystal/go-katapult/next"
+ "github.com/stretchr/testify/require"
+)
+
+func ptr[T any](v T) *T {
+ return &v
+}
+
+func TestDerefOrEmpty_string(t *testing.T) {
+ tests := []struct {
+ name string
+ in *string
+ want string
+ }{
+ {
+ name: "Nil input",
+ in: nil,
+ want: "",
+ },
+ {
+ name: "Non-nil input",
+ in: ptr("hello"),
+ want: "hello",
+ },
+ }
+
+ for _, tt := range tests {
+ t.Run(tt.name, func(t *testing.T) {
+ require.Equal(t, tt.want, next.DerefOrEmpty(tt.in))
+ })
+ }
+}
+
+func TestDerefOrEmpty_int(t *testing.T) {
+ tests := []struct {
+ name string
+ in *int
+ want int
+ }{
+ {
+ name: "Nil input",
+ in: nil,
+ want: 0,
+ },
+ {
+ name: "Non-nil input",
+ in: ptr(22),
+ want: 22,
+ },
+ }
+
+ for _, tt := range tests {
+ t.Run(tt.name, func(t *testing.T) {
+ require.Equal(t, tt.want, next.DerefOrEmpty(tt.in))
+ })
+ }
+}
+
+func TestDerefOrEmpty_float64(t *testing.T) {
+ tests := []struct {
+ name string
+ in *float64
+ want float64
+ }{
+ {
+ name: "Nil input",
+ in: nil,
+ want: 0.0,
+ },
+ {
+ name: "Non-nil input",
+ in: ptr(3.14),
+ want: 3.14,
+ },
+ }
+
+ for _, tt := range tests {
+ t.Run(tt.name, func(t *testing.T) {
+ require.Equal(t, tt.want, next.DerefOrEmpty(tt.in))
+ })
+ }
+}
+
+func TestDerefOrEmpty_slice(t *testing.T) {
+ tests := []struct {
+ name string
+ in *[]string
+ want []string
+ }{
+ {
+ name: "Nil input",
+ in: nil,
+ want: []string{},
+ },
+ {
+ name: "Non-nil input",
+ in: ptr([]string{"hello", "world"}),
+ want: []string{"hello", "world"},
+ },
+ }
+
+ for _, tt := range tests {
+ t.Run(tt.name, func(t *testing.T) {
+ require.Equal(t, tt.want, next.DerefOrEmpty(tt.in))
+ })
+ }
+}
+
+func TestDerefOrEmpty_map(t *testing.T) {
+ tests := []struct {
+ name string
+ in *map[string]int
+ want map[string]int
+ }{
+ {
+ name: "Nil input",
+ in: nil,
+ want: map[string]int{},
+ },
+ {
+ name: "Non-nil input",
+ in: ptr(map[string]int{"hello": 32}),
+ want: map[string]int{"hello": 32},
+ },
+ }
+
+ for _, tt := range tests {
+ t.Run(tt.name, func(t *testing.T) {
+ require.Equal(t, tt.want, next.DerefOrEmpty(tt.in))
+ })
+ }
+}
+
+func TestDerefOrEmpty_struct(t *testing.T) {
+ type testStruct struct {
+ Name string
+ Age int
+ }
+
+ tests := []struct {
+ name string
+ in *testStruct
+ want testStruct
+ }{
+ {
+ name: "Nil input",
+ in: nil,
+ want: testStruct{},
+ },
+ {
+ name: "Non-nil input",
+ in: ptr(testStruct{Name: "Alice", Age: 22}),
+ want: testStruct{Name: "Alice", Age: 22},
+ },
+ }
+
+ for _, tt := range tests {
+ t.Run(tt.name, func(t *testing.T) {
+ require.Equal(t, tt.want, next.DerefOrEmpty(tt.in))
+ })
+ }
+}