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GODRIVER-3574 Align BSON interface slice decoding with json package. #2075

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Merged
qingyang-hu merged 6 commits into from
Jun 4, 2025
Merged

GODRIVER-3574 Align BSON interface slice decoding with json package. #2075

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3551518
Align BSON interface slice decoding with json package.
qingyang-hu May 29, 2025
b57049b
Merge branch 'master' into godriver3574
qingyang-hu Jun 3, 2025
841cd96
add tests
qingyang-hu Jun 3, 2025
779d6b0
fix tests
qingyang-hu Jun 3, 2025
0bb71be
update comments
qingyang-hu Jun 4, 2025
033957f
fix typo
qingyang-hu Jun 4, 2025
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11 changes: 10 additions & 1 deletion bson/default_value_decoders.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1351,14 +1351,17 @@ func decodeDefault(dc DecodeContext, vr ValueReader, val reflect.Value) ([]refle
}

var elem reflect.Value
if vDecoder == nil {
if vDecoder == nil && idx < val.Len() {
elem = val.Index(idx).Elem()
switch {
case elem.Kind() != reflect.Ptr || elem.IsNil():
valueDecoder, err := dc.LookupDecoder(elem.Type())
if err != nil {
return nil, err
}
if !elem.CanSet() {
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@prestonvasquez prestonvasquez Jun 4, 2025

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This change is really nuanced. Can we add a comment here noting why we do this? "If an element is unsettable and allocated, it must be overwritten."

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@prestonvasquez prestonvasquez Jun 4, 2025

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I also suggest making the following changes to make this more readable:

isInterfaceSlice := eType.Kind() == reflect.Interface && val.Len() > 0

// If this is not an interface slice with pre-populated elements, we can look
// up the decoder for eType once.
var vDecoder ValueDecoder
if !isInterfaceSlice {
	vDecoder, err = dc.LookupDecoder(eType)
	if err != nil {
		return nil, err
	}
}

for {
	// ...
	if isInterfaceSlice && idx < val.Len() {
		// Decode into an existing interface{} slot.
		
		// ...
	} else {
		// For non-interface slices, or if we've exhuasted the pre-populated
		// slots, we create a fresh value.
		if vDecoder == nil {
			// ...
		}

		//...
	}
}

elem = reflect.New(elem.Type()).Elem()
}
err = valueDecoder.DecodeValue(dc, vr, elem)
if err != nil {
return nil, newDecodeError(strconv.Itoa(idx), err)
Expand All @@ -1380,6 +1383,12 @@ func decodeDefault(dc DecodeContext, vr ValueReader, val reflect.Value) ([]refle
}
}
} else {
if vDecoder == nil {
vDecoder, err = dc.LookupDecoder(eType)
if err != nil {
return nil, err
}
}
elem, err = decodeTypeOrValueWithInfo(vDecoder, dc, vr, eType)
if err != nil {
return nil, newDecodeError(strconv.Itoa(idx), err)
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