Kriskras99 commented on issue #400:
URL: https://github.com/apache/avro-rs/issues/400#issuecomment-3758844309
Sorry, that's my fault. `#schema_def` is something from the avro_derive
code. Here's a type expanded, so you can see what's going on:
```rust
pub struct Recursive {
field: Option<Box<Recursive>>,
}
impl AvroSchemaComponent for Recursive {
fn get_schema_in_ctxt(
named_schemas: &mut Names,
enclosing_namespace: &Option<String>,
) -> Schema {
let name = Name::new("Recursive")
.expect("Unable to parse schema name Recursive")
.fully_qualified_name(enclosing_namespace);
if named_schemas.contains_key(&name) {
Schema::Ref { name }
} else {
let enclosing_namespace = &name.namespace;
// Without this, this function would recurse forever and cause a
stackoverflow
named_schemas.insert(name.clone(), Schema::Ref { name:
name.clone() });
let schema = {
let schema_fields = vec![
RecordField::builder()
.name("field".to_string())
// This is the recursive call
.schema(<Option<Box<Recursive>>>::get_schema_in_ctxt(
named_schemas,
enclosing_namespace,
))
.build(),
];
Schema::Record(
RecordSchema::builder()
.name(name.clone())
.lookup(
schema_fields
.iter()
.map(|field| (field.name.clone(),
field.position))
.collect(),
)
.fields(schema_fields)
.build(),
)
};
named_schemas.insert(name, schema.clone());
schema
}
}
}
```
Note: it does not matter what is inserted into `named_schemas` the first
time, instead of a `Schema::Ref` it could also be a `Schema::Null`. The reason
that I insert a `Schema::Ref`, is that user implementations of
`AvroSchemaComponent` may depend on the type that is in `named_schemas`.
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