Disallow AgentTracer.forceRegister(null) (#11942)

Disallow AgentTracer.forceRegister(null)

Callers should pass NOOP_TRACER explicitly instead of null.

Co-authored-by: devflow.devflow-routing-intake <devflow.devflow-routing-intake@kubernetes.us1.ddbuild.io>

Author: mcculls

dd-java-agent/agent-debugger/src/test/java/com/datadog/debugger/agent/DebuggerTracerTest.java

@@ -20,7 +20,7 @@ class DebuggerTracerTest {
 
   @AfterEach
   public void after() {
-    AgentTracer.forceRegister(null);
+    AgentTracer.forceRegister(AgentTracer.NOOP_TRACER);
   }
 
   @Test
@@ -60,7 +60,7 @@ public void setError() {
 
   @Test
   public void noApi() {
-    AgentTracer.forceRegister(null);
+    AgentTracer.forceRegister(AgentTracer.NOOP_TRACER);
     ProbeStatusSink probeStatusSink = mock(ProbeStatusSink.class);
     DebuggerTracer debuggerTracer = new DebuggerTracer(probeStatusSink);
     DebuggerSpan span =

internal-api/src/main/java/datadog/trace/bootstrap/instrumentation/api/AgentTracer.java

@@ -258,6 +258,9 @@ public static synchronized void registerIfAbsent(final TracerAPI tracer) {
   }
 
   public static synchronized void forceRegister(TracerAPI tracer) {
+    if (tracer == null) {
+      throw new IllegalArgumentException("tracer must not be null, use NOOP_TRACER instead");
+    }
     provider = tracer;
   }