yonah/monstersirenfetch
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generic: emulate nullable string behaviour

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This fills the gap for nullable strings returned by the API.

Signed-off-by: Yonah <contrib@gensokyo.uk>
This commit is contained in:
Yonah 2025-09-17 07:47:51 +09:00
parent 7dd470f9ae
commit c2c4171a3a
Signed by: yonah
SSH Key Fingerprint: SHA256:vnQvK8+XXH9Tbni2AV1a/8qdVK/zPcXw52GM0ruQvwA
2 changed files with 55 additions and 19 deletions
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23
generic.go
View File

@ -13,6 +13,29 @@ type Response[T any] struct {
Data T `json:"data"`
}
// NullableString is a JSON string where its zero value behaves like null.
type NullableString string
func (s *NullableString) MarshalJSON() ([]byte, error) {
if *s == "" {
return []byte("null"), nil
}
return json.Marshal(string(*s))
}
func (s *NullableString) UnmarshalJSON(data []byte) (err error) {
var v *string
err = json.Unmarshal(data, &v)
if err == nil {
if v != nil {
*s = NullableString(*v)
} else {
*s = ""
}
}
return
}
// StringInt is a JSON string representing an integer.
type StringInt int

49
generic_test.go
View File

@ -11,13 +11,17 @@ import (
. "git.gensokyo.uk/yonah/monstersirenfetch"
)
func TestNullableString(t *testing.T) {
checkJSONRoundTripM(t, []jsonRoundTripTestCase[NullableString]{
{"zero", nil, `null`, ""},
{"string", nil, `"null"`, "null"},
{"invalid json", newSyntaxError("unexpected end of JSON input", 5), `"null`, "\x00"},
})
}
func TestStringInt(t *testing.T) {
testCases := []struct {
name string
wantErr error
data string
val int
}{
checkJSONRoundTripM(t, []jsonRoundTripTestCase[StringInt]{
{"valid long", nil, `"3735928559"`, 0xdeadbeef},
{"valid pad 4", nil, `"0000"`, 0},
{"valid 4", nil, `"1000"`, 1e3},
@ -26,13 +30,29 @@ func TestStringInt(t *testing.T) {
{"invalid json", newSyntaxError("unexpected end of JSON input", 11), `"3735928559`, -1},
{"invalid number", &strconv.NumError{Func: "Atoi", Num: ":3735928559", Err: strconv.ErrSyntax}, `":3735928559"`, -1},
})
}
func newSyntaxError(msg string, offset int64) *json.SyntaxError {
e := &json.SyntaxError{Offset: offset}
msgV := reflect.ValueOf(e).Elem().FieldByName("msg")
reflect.NewAt(msgV.Type(), unsafe.Pointer(msgV.UnsafeAddr())).Elem().SetString(msg)
return e
}
type jsonRoundTripTestCase[T comparable] struct {
name string
wantErr error
data string
val T
}
func checkJSONRoundTripM[T comparable](t *testing.T, testCases []jsonRoundTripTestCase[T]) {
for _, tc := range testCases {
t.Run(tc.name, func(t *testing.T) {
if tc.wantErr == nil {
t.Run("marshal", func(t *testing.T) {
v := StringInt(tc.val)
if got, err := json.Marshal(&v); err != nil {
if got, err := json.Marshal(&tc.val); err != nil {
t.Fatalf("Marshal: error = %v", err)
} else if string(got) != tc.data {
t.Errorf("Marshal: %s, want %s", string(got), tc.data)
@ -41,7 +61,7 @@ func TestStringInt(t *testing.T) {
}
t.Run("unmarshal", func(t *testing.T) {
var got StringInt
var got T
err := json.Unmarshal([]byte(tc.data), &got)
if !reflect.DeepEqual(err, tc.wantErr) {
@ -49,8 +69,8 @@ func TestStringInt(t *testing.T) {
}
if tc.wantErr == nil {
if int(got) != tc.val {
t.Errorf("Unmarshal: %d, want %d", got, tc.val)
if got != tc.val {
t.Errorf("Unmarshal: %v, want %v", got, tc.val)
}
}
})
@ -58,13 +78,6 @@ func TestStringInt(t *testing.T) {
}
}
func newSyntaxError(msg string, offset int64) *json.SyntaxError {
e := &json.SyntaxError{Offset: offset}
msgV := reflect.ValueOf(e).Elem().FieldByName("msg")
reflect.NewAt(msgV.Type(), unsafe.Pointer(msgV.UnsafeAddr())).Elem().SetString(msg)
return e
}
func checkJSONRoundTrip[T any](t *testing.T, v T, data []byte) {
t.Run("marshal", func(t *testing.T) {
buf := new(bytes.Buffer)