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| package utils | |
| import "encoding/json" | |
| type Optional[T any] struct { | |
| explicit bool | |
| hasValue bool | |
| value T | |
| } | |
| func (o *Optional[T]) UnmarshalJSON(b []byte) error { | |
| if len(b) == 0 { | |
| return nil | |
| } | |
| o.explicit = true | |
| if string(b) == "null" { | |
| return nil | |
| } | |
| o.hasValue = true | |
| return json.Unmarshal(b, &o.value) | |
| } | |
| func (o *Optional[T]) Explicit() bool { | |
| return o.explicit | |
| } | |
| func (o *Optional[T]) Value() *T { | |
| if !o.explicit || !o.hasValue { | |
| return nil | |
| } | |
| return &o.value | |
| } |
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| package utils | |
| import ( | |
| "encoding/json" | |
| "testing" | |
| "github.com/stretchr/testify/assert" | |
| "github.com/stretchr/testify/require" | |
| ) | |
| var ( | |
| _ json.Unmarshaler = &Optional[int]{} | |
| _ json.Unmarshaler = &Optional[string]{} | |
| ) | |
| type WithOptionals struct { | |
| IntField1 Optional[int] | |
| IntField2 Optional[int] `json:"int_field_2"` | |
| } | |
| func TestOptional(t *testing.T) { | |
| t.Run("Default should be implicit nulls", func(t *testing.T) { | |
| var data WithOptionals | |
| assert.False(t, data.IntField1.Explicit()) | |
| assert.Nil(t, data.IntField1.Value()) | |
| assert.False(t, data.IntField2.Explicit()) | |
| assert.Nil(t, data.IntField2.Value()) | |
| }) | |
| } | |
| func TestOptional_Unmarshal(t *testing.T) { | |
| t.Run("Implicit null", func(t *testing.T) { | |
| var data WithOptionals | |
| const text = `{}` | |
| err := json.Unmarshal([]byte(text), &data) | |
| require.NoError(t, err) | |
| assert.False(t, data.IntField1.Explicit()) | |
| assert.Nil(t, data.IntField1.Value()) | |
| assert.False(t, data.IntField2.Explicit()) | |
| assert.Nil(t, data.IntField2.Value()) | |
| }) | |
| t.Run("Explicit nulls", func(t *testing.T) { | |
| var data WithOptionals | |
| const text = `{ | |
| "IntField1": null, | |
| "int_field_2": null | |
| }` | |
| err := json.Unmarshal([]byte(text), &data) | |
| require.NoError(t, err) | |
| assert.True(t, data.IntField1.Explicit()) | |
| assert.Nil(t, data.IntField1.Value()) | |
| assert.True(t, data.IntField2.Explicit()) | |
| assert.Nil(t, data.IntField2.Value()) | |
| }) | |
| t.Run(`Explicit string "null" should fail`, func(t *testing.T) { | |
| var data WithOptionals | |
| const text = `{ | |
| "IntField1": "null", | |
| "int_field_2": "null" | |
| }` | |
| err := json.Unmarshal([]byte(text), &data) | |
| require.Error(t, err) | |
| }) | |
| t.Run("Happy scenario", func(t *testing.T) { | |
| var data WithOptionals | |
| const text = `{ | |
| "IntField1": 123, | |
| "int_field_2": 456 | |
| }` | |
| err := json.Unmarshal([]byte(text), &data) | |
| require.NoError(t, err) | |
| assert.True(t, data.IntField1.Explicit()) | |
| assert.Equal(t, 123, *data.IntField1.Value()) | |
| assert.True(t, data.IntField2.Explicit()) | |
| assert.Equal(t, 456, *data.IntField2.Value()) | |
| }) | |
| } |
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