Lucas Javaudin created AVRO-3646:
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Summary: Serialization / deserialization for enum with mixed
variants (with and without data)
Key: AVRO-3646
URL: https://issues.apache.org/jira/browse/AVRO-3646
Project: Apache Avro
Issue Type: Bug
Components: rust
Reporter: Lucas Javaudin
Consider the following example of what I call an "enum with mixed variants":
{code:java}
enum MixedExternalEnum {
Val1,
Val2(f32),
} {code}
For the two variants, this enum can be properly serialized to and deserialized
from a {{types::Value}} (using {{ser::to_value}} and {{{}de::from_value{}}}).
The problem is that the way they are represented as a \{{types::Value }}cannot
be represented using an Avro Schema.
The serialized version of {{MixedExternalEnum::Val1}} is
{code:java}
Value::Record(vec![("a".to_owned(), Value::Enum(0, "Val1".to_owned()))])
{code}
while the serialized version of {{MixedExternalEnum::Val2(0.0)}} is
{code:java}
Value::Record(vec![(
"a".to_owned(),
Value::Record(vec![
("type".to_owned(), Value::Enum(1, "Val2".to_owned())),
(
"value".to_owned(),
Value::Union(1, Box::new(Value::Float(0.0))),
),
]),
)])
{code}
As far as I know, there is no Avro Schema compatible with both possible values.
One solution I can think of is to change the serialization of
{{MixedExternalEnum::Val1}} to
{code:java}
Value::Record(vec![(
"a".to_owned(),
Value::Record(vec![
("type".to_owned(), Value::Enum(0, "Val1".to_owned())),
(
"value".to_owned(),
Value::Union(0, Box::new(Value::Null)),
),
]),
)])
{code}
A workaround is to replace {{Val1}} by {{Val1(())}} in the enum definition (see
AVRO-3645) but this can have undesirable effects for other parts of the code.
Then, it's another story for adjacently tagged, internally tagged and untagged
enum...
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