[GitHub] [beam] lostluck opened a new issue, #26066: [Bug][Go SDK]: Generic functions alias to same registered name in Go 1.20

["lostluck (via GitHub)" <gi...@apache.org>]

lostluck opened a new issue, #26066:
URL: https://github.com/apache/beam/issues/26066

   ### What happened?
   
   Changes in Go 1.20 lead to the "function name" of generic functions to have type substitutions registered as "..." instead of a concrete type. This can lead to aliasing of registered generic functions, even with different types.
   
   This affects the generic BSON coders in the mongodbio.
   https://github.com/apache/beam/blob/master/sdks/go/pkg/beam/io/mongodbio/coder.go#L30
   
   ```
   
   func init() {
   	beam.RegisterCoder(
   		reflect.TypeOf((*idRangeRestriction)(nil)).Elem(),
   		encodeBSON[idRangeRestriction],
   		decodeBSON[idRangeRestriction],
   	)
   	beam.RegisterCoder(
   		reflect.TypeOf((*idRange)(nil)).Elem(),
   		encodeBSON[idRange],
   		decodeBSON[idRange],
   	)
   }
   
   func encodeBSON[T any](in T) ([]byte, error) {
   	out, err := bson.Marshal(in)
   	if err != nil {
   		return nil, fmt.Errorf("error encoding BSON: %w", err)
   	}
   
   	return out, nil
   }
   
   func decodeBSON[T any](in []byte) (T, error) {
   	var out T
   	if err := bson.Unmarshal(in, &out); err != nil {
   		return out, fmt.Errorf("error decoding BSON: %w", err)
   	}
   
   	return out, nil
   }
   ```
   
   Fortunately a work around exists, by just wrapping the generic functions with a concrete function for use in the registrations instead.
   
   ```
   func encodeRestriction(in idRangeRestriction) ([]byte, error) {
   	return encodeBSON(in)
   }
   func decodeRestriction(in []byte) (idRangeRestriction, error) {
   	return decodeBSON[idRangeRestriction](in)
   }
   
   func encodeRange(in idRange) ([]byte, error) {
   	return encodeBSON(in)
   }
   func decodeRange(in []byte) (idRange, error) {
   	return decodeBSON[idRange](in)
   }
   ```
   
   This issue is to track and add a more permanent resilient fix into Beam itself.
   
   Likely in the reflectx and funcx packages and methods, but in particular for when wrapping a CustomCoder here. https://github.com/apache/beam/blob/master/sdks/go/pkg/beam/core/graph/coder/coder.go#L137
   
   ### Issue Priority
   
   Priority: 3 (minor)
   
   ### Issue Components
   
   - [ ] Component: Python SDK
   - [ ] Component: Java SDK
   - [X] Component: Go SDK
   - [ ] Component: Typescript SDK
   - [ ] Component: IO connector
   - [ ] Component: Beam examples
   - [ ] Component: Beam playground
   - [ ] Component: Beam katas
   - [ ] Component: Website
   - [ ] Component: Spark Runner
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