Add failing test for #343 (#666)

Author: cowtowncoder

avro/src/test/java/tools/jackson/dataformat/avro/tofix/SingleObjectEncoding343Test.java

@@ -0,0 +1,107 @@
+package tools.jackson.dataformat.avro.tofix;
+
+import java.io.ByteArrayOutputStream;
+import java.nio.ByteBuffer;
+
+import org.apache.avro.Schema;
+import org.apache.avro.generic.GenericData;
+import org.apache.avro.generic.GenericDatumWriter;
+import org.apache.avro.generic.GenericRecord;
+import org.apache.avro.io.BinaryEncoder;
+import org.apache.avro.io.DatumWriter;
+import org.apache.avro.io.EncoderFactory;
+import org.apache.avro.message.BinaryMessageEncoder;
+
+import org.junit.jupiter.api.Test;
+
+import tools.jackson.databind.JsonNode;
+import tools.jackson.dataformat.avro.AvroMapper;
+import tools.jackson.dataformat.avro.AvroSchema;
+import tools.jackson.dataformat.avro.testutil.failure.JacksonTestFailureExpected;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+/**
+ * Reproducer for [dataformats-binary#343]: decoding data encoded with Apache Avro's
+ * Single Object Encoding (magic bytes 0xC3 0x01 + 8-byte schema fingerprint + payload)
+ * fails with "Invalid length indicator for String: -98".
+ */
+public class SingleObjectEncoding343Test
+{
+    private static final String SCHEMA_JSON = "{"
+        + "\"type\": \"record\","
+        + "\"name\": \"SampleRecord\","
+        + "\"fields\": ["
+        + "  {\"name\": \"name\", \"type\": \"string\"}"
+        + "]}";
+
+    private final AvroMapper MAPPER = new AvroMapper();
+
+    /**
+     * Test showing the failure: data encoded with Apache Avro's BinaryMessageEncoder
+     * (Single Object Encoding) cannot be decoded by Jackson's AvroMapper.
+     * The first two bytes are the magic 0xC3 0x01 which decode as zigzag VarInt -98,
+     * causing "Invalid length indicator for String: -98".
+     */
+    @JacksonTestFailureExpected
+    @Test
+    public void testReadSingleObjectEncoding() throws Exception
+    {
+        Schema apacheSchema = new Schema.Parser().parse(SCHEMA_JSON);
+        AvroSchema jacksonSchema = new AvroSchema(apacheSchema);
+
+        // Encode using Apache Avro's Single Object Encoding (BinaryMessageEncoder),
+        // which is what SpecificRecord.toByteBuffer() uses in Apache Avro 1.8+.
+        // The encoded bytes start with magic: 0xC3 0x01
+        BinaryMessageEncoder<GenericRecord> encoder =
+                new BinaryMessageEncoder<>(GenericData.get(), apacheSchema);
+        GenericRecord record = new GenericData.Record(apacheSchema);
+        record.put("name", "apm");
+        ByteBuffer encoded = encoder.encode(record);
+        byte[] bytes = toByteArray(encoded);
+
+        // Verify the magic bytes are present (the root cause of the failure)
+        assertEquals((byte) 0xC3, bytes[0], "First magic byte should be 0xC3");
+        assertEquals((byte) 0x01, bytes[1], "Second magic byte should be 0x01");
+
+        // This currently fails with:
+        // "Invalid length indicator for String: -98"
+        // because Jackson tries to decode 0xC3 0x01 as a zigzag VarInt string length
+        JsonNode result = MAPPER.reader(jacksonSchema).readTree(bytes);
+        assertNotNull(result);
+        assertEquals("apm", result.get("name").asText());
+    }
+
+    /**
+     * Contrast: regular Avro binary encoding (NOT Single Object Encoding) works fine.
+     */
+    @Test
+    public void testReadRegularBinaryEncoding() throws Exception
+    {
+        Schema apacheSchema = new Schema.Parser().parse(SCHEMA_JSON);
+        AvroSchema jacksonSchema = new AvroSchema(apacheSchema);
+
+        // Encode using regular binary encoder (no SOE header)
+        ByteArrayOutputStream out = new ByteArrayOutputStream();
+        BinaryEncoder binaryEncoder = EncoderFactory.get().binaryEncoder(out, null);
+        DatumWriter<GenericRecord> writer = new GenericDatumWriter<>(apacheSchema);
+        GenericRecord record = new GenericData.Record(apacheSchema);
+        record.put("name", "apm");
+        writer.write(record, binaryEncoder);
+        binaryEncoder.flush();
+        byte[] bytes = out.toByteArray();
+
+        // First byte should be 0x06 (zigzag VarInt for length 3), not 0xC3
+        assertEquals((byte) 0x06, bytes[0]);
+
+        JsonNode result = MAPPER.reader(jacksonSchema).readTree(bytes);
+        assertNotNull(result);
+        assertEquals("apm", result.get("name").asText());
+    }
+
+    private static byte[] toByteArray(ByteBuffer buf) {
+        byte[] bytes = new byte[buf.remaining()];
+        buf.get(bytes);
+        return bytes;
+    }
+}