Prevent NPE in HttpClientDecorator.isAgentRequest for a null request

dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/decorator/HttpClientDecorator.java

@@ -58,6 +58,11 @@ public abstract class HttpClientDecorator<REQUEST, RESPONSE> extends UriBasedCli
    * not be traced to avoid self-tracing loops.
    */
   public boolean isAgentRequest(final REQUEST request) {
+    // Advice runs before the instrumented method's own argument validation, so a caller
+    // passing a null request must not NPE here — let the real method report that itself.
+    if (request == null) {
+      return false;
+    }
     return getRequestHeader(request, DATADOG_META_LANG_HEADER_NAME) != null
         || getRequestHeader(request, DD_CLIENT_LIBRARY_LANGUAGE_HEADER_NAME) != null;
   }

dd-java-agent/agent-bootstrap/src/test/java/datadog/trace/bootstrap/instrumentation/decorator/HttpClientDecoratorIsAgentRequestTest.java

@@ -0,0 +1,57 @@
+package datadog.trace.bootstrap.instrumentation.decorator;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+
+import java.net.URI;
+import java.net.URISyntaxException;
+import org.junit.jupiter.api.Test;
+
+class HttpClientDecoratorIsAgentRequestTest {
+
+  // Regression test: advice runs before the instrumented method's own argument validation, so a
+  // caller passing a null request (e.g. HttpClient.sendAsync(null, ...)) must not NPE inside
+  // isAgentRequest -> getRequestHeader. See
+  // datadog.trace.instrumentation.httpclient.SendAsyncAdvice.
+  @Test
+  void isAgentRequestOfNullRequestReturnsFalseInsteadOfThrowing() {
+    HttpClientDecorator<Object, Object> decorator =
+        new HttpClientDecorator<Object, Object>() {
+          @Override
+          protected String[] instrumentationNames() {
+            return new String[] {"test"};
+          }
+
+          @Override
+          protected CharSequence component() {
+            return "test-component";
+          }
+
+          @Override
+          protected String method(Object request) {
+            return null;
+          }
+
+          @Override
+          protected URI url(Object request) throws URISyntaxException {
+            return null;
+          }
+
+          @Override
+          protected int status(Object response) {
+            return 0;
+          }
+
+          @Override
+          protected String getRequestHeader(Object request, String headerName) {
+            throw new NullPointerException("should not be reached for a null request");
+          }
+
+          @Override
+          protected String getResponseHeader(Object response, String headerName) {
+            return null;
+          }
+        };
+
+    assertFalse(decorator.isAgentRequest(null));
+  }
+}