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Commit 31c2c6c

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Fix unmarshaler offset error in struct fields
When custom unmarshalers decoded container types in struct fields, the reflection decoder would fail with "no next offset available" when trying to advance to the next field.
1 parent a9dfa5e commit 31c2c6c

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4 files changed

+89
-10
lines changed

4 files changed

+89
-10
lines changed

‎CHANGELOG.md‎

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@@ -1,5 +1,12 @@
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# Changes
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## 2.0.0-beta.8 - 2025年07月15日
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- Fixed "no next offset available" error that occurred when using custom
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unmarshalers that decode container types (maps, slices) in struct fields.
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The reflection decoder now correctly calculates field positions when
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advancing to the next field after custom unmarshaling.
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## 2.0.0-beta.7 - 2025年07月07日
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* Update capitalization of "uint" in `ReadUInt*` to match `KindUint*` as well

‎internal/decoder/decoder.go‎

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@@ -1,7 +1,6 @@
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package decoder
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import (
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"errors"
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"fmt"
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"iter"
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@@ -370,13 +369,6 @@ func (d *Decoder) setNextOffset(offset uint) {
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}
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}
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func (d *Decoder) getNextOffset() (uint, error) {
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if !d.hasNextOffset {
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return 0, errors.New("no next offset available")
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}
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return d.nextOffset, nil
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}
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func unexpectedKindErr(expectedKind, actualKind Kind) error {
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return fmt.Errorf("unexpected kind %d, expected %d", actualKind, expectedKind)
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}

‎internal/decoder/nested_unmarshaler_test.go‎

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Original file line numberDiff line numberDiff line change
@@ -3,6 +3,7 @@ package decoder
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import (
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"testing"
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"github.com/stretchr/testify/assert"
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"github.com/stretchr/testify/require"
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)
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@@ -220,3 +221,82 @@ func TestNestedUnmarshalerInMap(t *testing.T) {
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require.Equal(t, "map:value2", result["key2"].Data)
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})
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}
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// testMapIterator uses ReadMap() iterator to simulate mmdbtype.Map behavior.
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type testMapIterator struct {
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Values map[string]string
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custom bool
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}
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func (m *testMapIterator) UnmarshalMaxMindDB(d *Decoder) error {
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m.custom = true
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iter, size, err := d.ReadMap()
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if err != nil {
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return err
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}
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m.Values = make(map[string]string, size)
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for key, iterErr := range iter {
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if iterErr != nil {
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return iterErr
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}
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// Read the value as a string
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value, err := d.ReadString()
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if err != nil {
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return err
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}
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m.Values[string(key)] = value
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}
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return nil
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}
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// TestCustomUnmarshalerWithIterator tests that custom unmarshalers using iterators
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// work correctly in struct fields. This reproduces the original "no next offset available"
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// issue that occurred when mmdbtype.Map was used in structs.
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func TestCustomUnmarshalerWithIterator(t *testing.T) {
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type Record struct {
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Name string
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Location testMapIterator // This field uses ReadMap() iterator
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Country string
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}
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data := []byte{
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// Map with 3 items
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0xe3,
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// Key "Name"
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0x44, 'N', 'a', 'm', 'e',
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// Value "Test" (string)
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0x44, 'T', 'e', 's', 't',
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// Key "Location"
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0x48, 'L', 'o', 'c', 'a', 't', 'i', 'o', 'n',
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// Value: Map with 2 items (latitude and longitude)
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0xe2,
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// Key "lat"
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0x43, 'l', 'a', 't',
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// Value "40.7"
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0x44, '4', '0', '.', '7',
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// Key "lng"
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0x43, 'l', 'n', 'g',
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// Value "-74.0"
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0x45, '-', '7', '4', '.', '0',
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// Key "Country"
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0x47, 'C', 'o', 'u', 'n', 't', 'r', 'y',
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// Value "US"
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0x42, 'U', 'S',
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}
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d := New(data)
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var result Record
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err := d.Decode(0, &result)
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require.NoError(t, err)
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require.Equal(t, "Test", result.Name)
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assert.True(t, result.Location.custom, "Custom unmarshaler should be called")
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assert.Len(t, result.Location.Values, 2)
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assert.Equal(t, "40.7", result.Location.Values["lat"])
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assert.Equal(t, "-74.0", result.Location.Values["lng"])
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assert.Equal(t, "US", result.Country)
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}

‎internal/decoder/reflection.go‎

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Original file line numberDiff line numberDiff line change
@@ -64,7 +64,7 @@ func (d *ReflectionDecoder) Decode(offset uint, v any) error {
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return mmdberrors.WrapWithContext(err, offset, nil)
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}
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// DecodePath decodes the data value at offset and stores the value assocated
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// DecodePath decodes the data value at offset and stores the value associated
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// with the path in the value pointed at by v.
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func (d *ReflectionDecoder) DecodePath(
7070
offset uint,
@@ -300,7 +300,7 @@ func (d *ReflectionDecoder) decodeValue(
300300
if err := unmarshaler.UnmarshalMaxMindDB(decoder); err != nil {
301301
return 0, err
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}
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return decoder.getNextOffset()
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return d.nextValueOffset(offset, 1)
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}
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}
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