Showcase self-referential writer pattern in tests

serde_avro_fast/Cargo.toml

@@ -38,6 +38,7 @@
 	apache-avro = { version = "0.14", features = ["bzip", "snappy", "xz", "zstandard"] }
 	criterion = "0.5"
 	lazy_static = "1"
+	ouroboros = "0.18"
 	paste = "1"
 	pretty_assertions = "1"
 	serde-tuple-vec-map = "1"

serde_avro_fast/tests/self_referential_writer.rs

@@ -0,0 +1,80 @@
+use {
+	serde::Serialize,
+	serde_avro_derive::BuildSchema,
+	serde_avro_fast::{ser::SerializerConfig, Schema},
+};
+
+#[derive(Serialize, BuildSchema)]
+struct Bar {
+	a: i32,
+	b: String,
+}
+
+#[ouroboros::self_referencing]
+struct Writer<'schema> {
+	serializer_config: SerializerConfig<'schema>,
+	#[borrows(mut serializer_config)]
+	#[covariant]
+	writer: serde_avro_fast::object_container_file_encoding::Writer<'this, 'schema, Vec<u8>>,
+}
+
+fn build_writer() -> Writer<'static> {
+	lazy_static::lazy_static! {
+		static ref SCHEMA: Schema = Bar::schema().unwrap();
+	}
+	Writer::new(SerializerConfig::new(&*SCHEMA), |serializer_config| {
+		serde_avro_fast::object_container_file_encoding::WriterBuilder::new(serializer_config)
+			.sync_marker({
+				// make test deterministic
+				[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16]
+			})
+			.build(Vec::new())
+			.unwrap()
+	})
+}
+
+#[test]
+fn test_owned_writer() {
+	let values = [
+		&Bar {
+			a: 1,
+			b: "foo".to_string(),
+		},
+		&Bar {
+			a: 2,
+			b: "bar".to_string(),
+		},
+	];
+
+	let mut writer = build_writer();
+	for b in values {
+		writer.with_writer_mut(|w| w.serialize(b).unwrap());
+	}
+
+	let finished_written_buffer: Vec<u8> = writer
+		.with_writer_mut(|w| -> Result<_, serde_avro_fast::ser::SerError> {
+			w.finish_block()?;
+			Ok(std::mem::replace(w.inner_mut(), Vec::new()))
+		})
+		.unwrap();
+
+	// In case we want to re-use it
+	let _source_serializer_config: SerializerConfig = writer.into_heads().serializer_config;
+
+	assert_eq!(
+		finished_written_buffer,
+		&[
+			79, 98, 106, 1, 2, 22, 97, 118, 114, 111, 46, 115, 99, 104, 101, 109, 97, 240, 1, 123,
+			34, 116, 121, 112, 101, 34, 58, 34, 114, 101, 99, 111, 114, 100, 34, 44, 34, 110, 97,
+			109, 101, 34, 58, 34, 115, 101, 108, 102, 95, 114, 101, 102, 101, 114, 101, 110, 116,
+			105, 97, 108, 95, 119, 114, 105, 116, 101, 114, 46, 66, 97, 114, 34, 44, 34, 102, 105,
+			101, 108, 100, 115, 34, 58, 91, 123, 34, 110, 97, 109, 101, 34, 58, 34, 97, 34, 44, 34,
+			116, 121, 112, 101, 34, 58, 34, 105, 110, 116, 34, 125, 44, 123, 34, 110, 97, 109, 101,
+			34, 58, 34, 98, 34, 44, 34, 116, 121, 112, 101, 34, 58, 34, 115, 116, 114, 105, 110,
+			103, 34, 125, 93, 125, 2, 20, 97, 118, 114, 111, 46, 99, 111, 100, 101, 99, 8, 110,
+			117, 108, 108, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 4, 20, 2, 6,
+			102, 111, 111, 4, 6, 98, 97, 114, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,
+			16
+		]
+	)
+}