Ensure backwards compatibility

Author: mpkorstanje

junit-platform-engine/src/main/java/org/junit/platform/engine/UniqueId.java

@@ -12,6 +12,11 @@
 
 import static org.apiguardian.api.API.Status.STABLE;
 
+import java.io.IOException;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+import java.io.ObjectStreamClass;
+import java.io.ObjectStreamField;
 import java.io.Serial;
 import java.io.Serializable;
 import java.lang.ref.SoftReference;
@@ -38,7 +43,12 @@
 public final class UniqueId implements Cloneable, Serializable {
 
 	@Serial
-	private static final long serialVersionUID = 2L;
+	private static final long serialVersionUID = 1L;
+
+	@Serial
+	@SuppressWarnings("UnusedVariable")
+	private static final ObjectStreamField[] serialPersistentFields = ObjectStreamClass.lookup(
+		SerializedForm.class).getFields();
 
 	private static final String ENGINE_SEGMENT_TYPE = "engine";
 
@@ -82,8 +92,10 @@ public static UniqueId root(String segmentType, String value) {
 		return new UniqueId(new Segment(segmentType, value));
 	}
 
-	@SuppressWarnings({ "serial", "RedundantSuppression" }) // always used with serializable implementation (List.copyOf())
-	private final List<Segment> segments;
+	@SuppressWarnings({ "serial", "RedundantSuppression" })
+	// always used with serializable implementation (List.copyOf())
+	// This is effectively final but not technically due to late initialization when deserializing
+	private /* final */ List<Segment> segments;
 
 	// lazily computed
 	private transient int hashCode;
@@ -227,6 +239,18 @@ protected Object clone() throws CloneNotSupportedException {
 		return super.clone();
 	}
 
+	@Serial
+	private void writeObject(ObjectOutputStream s) throws IOException {
+		SerializedForm serializedForm = new SerializedForm(this);
+		serializedForm.serialize(s);
+	}
+
+	@Serial
+	private void readObject(ObjectInputStream s) throws ClassNotFoundException, IOException {
+		SerializedForm serializedForm = SerializedForm.deserialize(s);
+		segments = serializedForm.segments;
+	}
+
 	@Override
 	public boolean equals(Object o) {
 		if (this == o) {
@@ -354,4 +378,42 @@ public String toString() {
 
 	}
 
+	/**
+	 * Represents the serialized output of {@code UniqueId}. The fields on this
+	 * class match the fields that {@code UniqueId} had prior to 6.1.
+	 */
+	private static final class SerializedForm implements Serializable {
+
+		@Serial
+		private static final long serialVersionUID = 1L;
+
+		@SuppressWarnings({ "serial", "RedundantSuppression" })
+		// always used with serializable implementation (List.copyOf())
+		private final List<Segment> segments;
+		private final UniqueIdFormat uniqueIdFormat;
+
+		SerializedForm(UniqueId uniqueId) {
+			this.segments = uniqueId.segments;
+			this.uniqueIdFormat = UniqueIdFormat.getDefault();
+		}
+
+		@SuppressWarnings("unchecked")
+		private SerializedForm(ObjectInputStream.GetField fields) throws IOException, ClassNotFoundException {
+			this.segments = (List<Segment>) fields.get("segments", null);
+			this.uniqueIdFormat = UniqueIdFormat.getDefault();
+		}
+
+		void serialize(ObjectOutputStream s) throws IOException {
+			ObjectOutputStream.PutField fields = s.putFields();
+			fields.put("segments", segments);
+			fields.put("uniqueIdFormat", uniqueIdFormat);
+			s.writeFields();
+		}
+
+		static SerializedForm deserialize(ObjectInputStream s) throws IOException, ClassNotFoundException {
+			ObjectInputStream.GetField fields = s.readFields();
+			return new SerializedForm(fields);
+		}
+	}
+
 }

platform-tests/src/test/java/org/junit/platform/engine/UniqueIdTests.java

@@ -18,6 +18,12 @@
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.junit.platform.commons.test.PreconditionAssertions.assertPreconditionViolationFor;
 
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+import java.util.Base64;
 import java.util.Optional;
 
 import org.junit.jupiter.api.Nested;
@@ -292,6 +298,75 @@ void removesLastSegment() {
 
 	}
 
+	@Nested
+	class Serialization {
+
+		final UniqueId uniqueId = UniqueId.root("engine", "junit-jupiter");
+
+		@Test
+		void roundTrip() throws IOException, ClassNotFoundException {
+			var bytesOut = new ByteArrayOutputStream();
+			var out = new ObjectOutputStream(bytesOut);
+			out.writeObject(uniqueId);
+
+			var bytesIn = new ByteArrayInputStream(bytesOut.toByteArray());
+			var in = new ObjectInputStream(bytesIn);
+			var actual = in.readObject();
+
+			assertEquals(uniqueId, actual);
+			assertEquals(uniqueId.toString(), actual.toString());
+		}
+
+		@Test
+		void deserializeromJunit60() throws IOException, ClassNotFoundException {
+			var uniqueIdFromJunit60 = Base64.getMimeDecoder().decode("""
+					rO0ABXNyACJvcmcuanVuaXQucGxhdGZvcm0uZW5naW5lLlVuaXF1ZUlkAAAAAAAAAAECAAJMAAhzZWdtZW50c3QAEExqYXZhL3V0
+					aWwvTGlzdDtMAA51bmlxdWVJZEZvcm1hdHQAKkxvcmcvanVuaXQvcGxhdGZvcm0vZW5naW5lL1VuaXF1ZUlkRm9ybWF0O3hwc3IA
+					EWphdmEudXRpbC5Db2xsU2VyV46rtjobqBEDAAFJAAN0YWd4cAAAAAF3BAAAAAFzcgAqb3JnLmp1bml0LnBsYXRmb3JtLmVuZ2lu
+					ZS5VbmlxdWVJZCRTZWdtZW50AAAAAAAAAAECAAJMAAR0eXBldAASTGphdmEvbGFuZy9TdHJpbmc7TAAFdmFsdWVxAH4AB3hwdAAG
+					ZW5naW5ldAANanVuaXQtanVwaXRlcnhzcgAob3JnLmp1bml0LnBsYXRmb3JtLmVuZ2luZS5VbmlxdWVJZEZvcm1hdAAAAAAAAAAB
+					AgAGQwAMY2xvc2VTZWdtZW50QwALb3BlblNlZ21lbnRDABBzZWdtZW50RGVsaW1pdGVyQwASdHlwZVZhbHVlU2VwYXJhdG9yTAAT
+					ZW5jb2RlZENoYXJhY3Rlck1hcHQAE0xqYXZhL3V0aWwvSGFzaE1hcDtMAA5zZWdtZW50UGF0dGVybnQAGUxqYXZhL3V0aWwvcmVn
+					ZXgvUGF0dGVybjt4cABdAFsALwA6c3IAEWphdmEudXRpbC5IYXNoTWFwBQfawcMWYNEDAAJGAApsb2FkRmFjdG9ySQAJdGhyZXNo
+					b2xkeHA/QAAAAAAADHcIAAAAEAAAAAZzcgATamF2YS5sYW5nLkNoYXJhY3RlcjSLR9lrGiZ4AgABQwAFdmFsdWV4cAAldAADJTI1
+					c3EAfgARADp0AAMlM0FzcQB+ABEAW3QAAyU1QnNxAH4AEQArdAADJTJCc3EAfgARAF10AAMlNURzcQB+ABEAL3QAAyUyRnhzcgAX
+					amF2YS51dGlsLnJlZ2V4LlBhdHRlcm5GZ9VrbkkCDQIAAkkABWZsYWdzTAAHcGF0dGVybnEAfgAHeHAAAAAgdAAXXFFbXEUoLisp
+					XFE6XEUoLispXFFdXEU=""");
+
+			var bytesIn = new ByteArrayInputStream(uniqueIdFromJunit60);
+			var in = new ObjectInputStream(bytesIn);
+			var actual = in.readObject();
+
+			assertEquals(uniqueId, actual);
+			assertEquals(uniqueId.toString(), actual.toString());
+		}
+
+		@Test
+		void deserializeFromJunit60IgnoresCustomFormat() throws IOException, ClassNotFoundException {
+			var uniqueIdWithCustomFormatFromJunit60 = Base64.getMimeDecoder().decode("""
+					rO0ABXNyACJvcmcuanVuaXQucGxhdGZvcm0uZW5naW5lLlVuaXF1ZUlkAAAAAAAAAAECAAJMAAhzZWdtZW50c3QAEExqYXZhL3V0
+					aWwvTGlzdDtMAA51bmlxdWVJZEZvcm1hdHQAKkxvcmcvanVuaXQvcGxhdGZvcm0vZW5naW5lL1VuaXF1ZUlkRm9ybWF0O3hwc3IA
+					EWphdmEudXRpbC5Db2xsU2VyV46rtjobqBEDAAFJAAN0YWd4cAAAAAF3BAAAAAFzcgAqb3JnLmp1bml0LnBsYXRmb3JtLmVuZ2lu
+					ZS5VbmlxdWVJZCRTZWdtZW50AAAAAAAAAAECAAJMAAR0eXBldAASTGphdmEvbGFuZy9TdHJpbmc7TAAFdmFsdWVxAH4AB3hwdAAG
+					ZW5naW5ldAANanVuaXQtanVwaXRlcnhzcgAob3JnLmp1bml0LnBsYXRmb3JtLmVuZ2luZS5VbmlxdWVJZEZvcm1hdAAAAAAAAAAB
+					AgAGQwAMY2xvc2VTZWdtZW50QwALb3BlblNlZ21lbnRDABBzZWdtZW50RGVsaW1pdGVyQwASdHlwZVZhbHVlU2VwYXJhdG9yTAAT
+					ZW5jb2RlZENoYXJhY3Rlck1hcHQAE0xqYXZhL3V0aWwvSGFzaE1hcDtMAA5zZWdtZW50UGF0dGVybnQAGUxqYXZhL3V0aWwvcmVn
+					ZXgvUGF0dGVybjt4cAB9AHsALAA9c3IAEWphdmEudXRpbC5IYXNoTWFwBQfawcMWYNEDAAJGAApsb2FkRmFjdG9ySQAJdGhyZXNo
+					b2xkeHA/QAAAAAAADHcIAAAAEAAAAAZzcgATamF2YS5sYW5nLkNoYXJhY3RlcjSLR9lrGiZ4AgABQwAFdmFsdWV4cAAldAADJTI1
+					c3EAfgARAHt0AAMlN0JzcQB+ABEAK3QAAyUyQnNxAH4AEQAsdAADJTJDc3EAfgARAH10AAMlN0RzcQB+ABEAPXQAAyUzRHhzcgAX
+					amF2YS51dGlsLnJlZ2V4LlBhdHRlcm5GZ9VrbkkCDQIAAkkABWZsYWdzTAAHcGF0dGVybnEAfgAHeHAAAAAgdAAXXFF7XEUoLisp
+					XFE9XEUoLispXFF9XEU=""");
+
+			var bytesIn = new ByteArrayInputStream(uniqueIdWithCustomFormatFromJunit60);
+			var in = new ObjectInputStream(bytesIn);
+			var actual = in.readObject();
+
+			assertEquals(uniqueId, actual);
+			assertEquals(uniqueId.toString(), actual.toString());
+		}
+
+	}
+
 	private static void assertSegment(Segment segment, String expectedType, String expectedValue) {
 		assertEquals(expectedType, segment.getType(), "segment type");
 		assertEquals(expectedValue, segment.getValue(), "segment value");