Fix NullPointerException in ExceptionProbe (#11051)

Fix NullPointerException in ExceptionProbe

getInnerMostThrowable can return null if there is cycle in causes
need to check for function return

fix test

Co-authored-by: jean-philippe.bempel <jean-philippe.bempel@datadoghq.com>

Author: jpbempel

dd-java-agent/agent-debugger/src/main/java/com/datadog/debugger/probe/ExceptionProbe.java

@@ -95,6 +95,10 @@ public void evaluate(
       return;
     }
     Throwable innerMostThrowable = getInnerMostThrowable(throwable);
+    if (innerMostThrowable == null) {
+      LOGGER.debug("Cannot get inner most throwable (cycle?)");
+      return;
+    }
     String fingerprint =
         Fingerprinter.fingerprint(innerMostThrowable, exceptionProbeManager.getClassNameFilter());
     if (exceptionProbeManager.shouldCaptureException(fingerprint)) {

dd-java-agent/agent-debugger/src/test/java/com/datadog/debugger/util/ExceptionHelperTest.java

@@ -2,6 +2,7 @@
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.mockito.ArgumentMatchers.anyString;
 import static org.mockito.Mockito.doAnswer;
@@ -74,7 +75,7 @@ public void foldExceptionStackTrace() {
     String strStackTrace = ExceptionHelper.foldExceptionStackTrace(new Exception());
     assertTrue(
         strStackTrace.startsWith(
-            "java.lang.Exception at com.datadog.debugger.util.ExceptionHelperTest.foldExceptionStackTrace(ExceptionHelperTest.java:74) at "),
+            "java.lang.Exception at com.datadog.debugger.util.ExceptionHelperTest.foldExceptionStackTrace(ExceptionHelperTest.java:75) at "),
         strStackTrace);
     assertFalse(strStackTrace.contains("\n"));
     assertFalse(strStackTrace.contains("\t"));
@@ -96,6 +97,10 @@ public void innerMostException() {
     assertEquals(nested, exceptions.pollLast());
     assertEquals(nested.getCause(), exceptions.pollLast());
     assertEquals(nested.getCause().getCause(), exceptions.pollLast());
+    // create a cycle and make sure we handle it gracefully
+    Exception ex2 = new RuntimeException("test2", ex);
+    ex.initCause(ex2);
+    assertNull(ExceptionHelper.getInnerMostThrowable(ex2));
   }
 
   @Test