Done first pass

kernel/kernel-api/src/main/java/io/delta/kernel/internal/metrics/MetricsReportSerializers.java → kernel/kernel-api/src/main/java/io/delta/kernel/internal/metrics/MetricsReportSerializer.java

@@ -26,46 +26,34 @@
 import io.delta.kernel.expressions.Column;
 import io.delta.kernel.expressions.Predicate;
 import io.delta.kernel.metrics.MetricsReport;
-import io.delta.kernel.metrics.ScanReport;
-import io.delta.kernel.metrics.SnapshotReport;
-import io.delta.kernel.metrics.TransactionReport;
 import io.delta.kernel.types.StructType;
 import java.io.IOException;
 
 /** Defines JSON serializers for {@link MetricsReport} types */
-public final class MetricsReportSerializers {
+public final class MetricsReportSerializer {
 
   /////////////////
   // Public APIs //
   /////////////////
 
   /**
-   * Serializes a {@link SnapshotReport} to a JSON string
+   * Serializes any {@link MetricsReport} to a JSON string using the configured ObjectMapper. This
+   * method works for any report type that has proper Jackson annotations.
    *
-   * @throws JsonProcessingException
-   */
-  public static String serializeSnapshotReport(SnapshotReport snapshotReport)
-      throws JsonProcessingException {
-    return OBJECT_MAPPER.writeValueAsString(snapshotReport);
-  }
-
-  /**
-   * Serializes a {@link ScanReport} to a JSON string
+   * <p>For successful serialization, the report class should have:
    *
-   * @throws JsonProcessingException
-   */
-  public static String serializeScanReport(ScanReport scanReport) throws JsonProcessingException {
-    return OBJECT_MAPPER.writeValueAsString(scanReport);
-  }
-
-  /**
-   * Serializes a {@link TransactionReport} to a JSON string
+   * <ul>
+   *   <li>Public fields or public getter methods
+   *   <li>No circular references in the object graph
+   *   <li>Fields with types supported by Jackson (primitives, collections, or types with registered
+   *       serializers)
+   * </ul>
    *
-   * @throws JsonProcessingException
+   * @throws JsonProcessingException if the report cannot be serialized (e.g., circular references,
+   *     unsupported types, or inaccessible fields)
    */
-  public static String serializeTransactionReport(TransactionReport transactionReport)
-      throws JsonProcessingException {
-    return OBJECT_MAPPER.writeValueAsString(transactionReport);
+  public static String serializeMetricsReport(MetricsReport report) throws JsonProcessingException {
+    return OBJECT_MAPPER.writeValueAsString(report);
   }
 
   /////////////////////////////////
@@ -96,5 +84,5 @@ public void serialize(Column value, JsonGenerator gen, SerializerProvider serial
     }
   }
 
-  private MetricsReportSerializers() {}
+  private MetricsReportSerializer() {}
 }

kernel/kernel-api/src/test/scala/io/delta/kernel/internal/metrics/MetricsReportSerializerSuite.scala

@@ -69,7 +69,7 @@ class MetricsReportSerializerSuite extends AnyFunSuite {
          |}
          |}
          |""".stripMargin.replaceAll("\n", "")
-    assert(expectedJson == MetricsReportSerializers.serializeSnapshotReport(snapshotReport))
+    assert(expectedJson == MetricsReportSerializer.serializeMetricsReport(snapshotReport))
   }
 
   test("SnapshotReport serializer") {
@@ -106,7 +106,7 @@ class MetricsReportSerializerSuite extends AnyFunSuite {
         |}
         |}
         |""".stripMargin.replaceAll("\n", "")
-    assert(expectedJson == MetricsReportSerializers.serializeSnapshotReport(snapshotReport1))
+    assert(expectedJson == MetricsReportSerializer.serializeMetricsReport(snapshotReport1))
 
     // Check with test function
     testSnapshotReport(snapshotReport1)
@@ -152,7 +152,7 @@ class MetricsReportSerializerSuite extends AnyFunSuite {
          |}
          |}
          |""".stripMargin.replaceAll("\n", "")
-    assert(expectedJson == MetricsReportSerializers.serializeTransactionReport(transactionReport))
+    assert(expectedJson == MetricsReportSerializer.serializeMetricsReport(transactionReport))
   }
 
   test("TransactionReport serializer") {
@@ -204,7 +204,7 @@ class MetricsReportSerializerSuite extends AnyFunSuite {
          |}
          |}
          |""".stripMargin.replaceAll("\n", "")
-    assert(expectedJson == MetricsReportSerializers.serializeTransactionReport(transactionReport1))
+    assert(expectedJson == MetricsReportSerializer.serializeMetricsReport(transactionReport1))
     // Check with test function
     testTransactionReport(transactionReport1)
 
@@ -257,7 +257,7 @@ class MetricsReportSerializerSuite extends AnyFunSuite {
          |}
          |}
          |""".stripMargin.replaceAll("\n", "")
-    assert(expectedJson == MetricsReportSerializers.serializeScanReport(scanReport))
+    assert(expectedJson == MetricsReportSerializer.serializeMetricsReport(scanReport))
   }
 
   test("ScanReport serializer") {
@@ -319,7 +319,7 @@ class MetricsReportSerializerSuite extends AnyFunSuite {
          |}
          |}
          |""".stripMargin.replaceAll("\n", "")
-    assert(expectedJson == MetricsReportSerializers.serializeScanReport(scanReport1))
+    assert(expectedJson == MetricsReportSerializer.serializeMetricsReport(scanReport1))
 
     // Check with test function
     testScanReport(scanReport1)
@@ -339,4 +339,28 @@ class MetricsReportSerializerSuite extends AnyFunSuite {
       Optional.empty())
     testScanReport(scanReport2)
   }
+
+  test("Generic serializer handles custom/new report types") {
+    // This test demonstrates that any custom MetricsReport implementation with proper
+    // Jackson annotations can be serialized without modifying MetricsReportSerializer
+
+    val fooReport = new FooReport("bar-value", 42, "zap-value")
+
+    val actualJson = MetricsReportSerializer.serializeMetricsReport(fooReport)
+
+    val expectedJson = """{"bar":"bar-value","zip":42,"zap":"zap-value"}"""
+
+    assert(expectedJson == actualJson)
+  }
 }
+
+/**
+ * Example custom report type demonstrating extensibility.
+ * Uses public fields (via @BeanProperty) to work with Jackson, like UcCommitTelemetry.Report.
+ */
+@com.fasterxml.jackson.annotation.JsonPropertyOrder(Array("bar", "zip", "zap"))
+class FooReport(
+    @scala.beans.BeanProperty val bar: String,
+    @scala.beans.BeanProperty val zip: Int,
+    @scala.beans.BeanProperty val zap: String)
+    extends io.delta.kernel.metrics.MetricsReport

kernel/kernel-defaults/src/main/java/io/delta/kernel/defaults/engine/LoggingMetricsReporter.java

@@ -17,11 +17,8 @@
 
 import com.fasterxml.jackson.core.JsonProcessingException;
 import io.delta.kernel.engine.MetricsReporter;
-import io.delta.kernel.internal.metrics.MetricsReportSerializers;
+import io.delta.kernel.internal.metrics.MetricsReportSerializer;
 import io.delta.kernel.metrics.MetricsReport;
-import io.delta.kernel.metrics.ScanReport;
-import io.delta.kernel.metrics.SnapshotReport;
-import io.delta.kernel.metrics.TransactionReport;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -36,23 +33,8 @@ public class LoggingMetricsReporter implements MetricsReporter {
   @Override
   public void report(MetricsReport report) {
     try {
-      if (report instanceof SnapshotReport) {
-        logger.info(
-            "SnapshotReport = {}",
-            MetricsReportSerializers.serializeSnapshotReport((SnapshotReport) report));
-      } else if (report instanceof ScanReport) {
-        logger.info(
-            "ScanReport = {}", MetricsReportSerializers.serializeScanReport((ScanReport) report));
-      } else if (report instanceof TransactionReport) {
-        logger.info(
-            "TransactionReport = {}",
-            MetricsReportSerializers.serializeTransactionReport((TransactionReport) report));
-      } else {
-        logger.info(
-            "{} = [{} does not support serializing this type of MetricReport]",
-            report.getClass(),
-            this.getClass());
-      }
+      final String reportType = report.getClass().getSimpleName();
+      logger.info("{} = {}", reportType, MetricsReportSerializer.serializeMetricsReport(report));
     } catch (JsonProcessingException e) {
       logger.info("Encountered exception while serializing report {}: {}", report, e);
     }