fix(otel): validate config before consuming provider builder

otel-plugin/src/main/java/software/amazon/lambda/durable/otel/ExecutionOtelPlugin.java

@@ -19,6 +19,7 @@
 import io.opentelemetry.sdk.trace.SdkTracerProvider;
 import io.opentelemetry.sdk.trace.SdkTracerProviderBuilder;
 import java.time.Instant;
+import java.util.Objects;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.TimeUnit;
 import org.slf4j.Logger;
@@ -175,6 +176,7 @@ public ExecutionOtelPlugin() {
      * @param config the plugin configuration
      */
     public ExecutionOtelPlugin(SdkTracerProviderBuilder tracerProviderBuilder, OtelPluginConfig config) {
+        Objects.requireNonNull(config, "config must not be null");
         this.idGenerator = DeterministicIdGenerator.installOn(tracerProviderBuilder);
         // Wrap the configured sampler so durable spans use the execution's single precomputed decision.
         DurableSampler.installOn(tracerProviderBuilder);
@@ -196,6 +198,7 @@ public ExecutionOtelPlugin(SdkTracerProviderBuilder tracerProviderBuilder, OtelP
      * @param config the plugin configuration
      */
     public ExecutionOtelPlugin(OtelPluginConfig config) {
+        Objects.requireNonNull(config, "config must not be null");
         this.contextExtractor = config.contextExtractor();
         this.enableMdc = config.enableMdc();
         this.workflowSpanName = config.workflowSpanName();

otel-plugin/src/main/java/software/amazon/lambda/durable/otel/InvocationOtelPlugin.java

@@ -19,6 +19,7 @@
 import io.opentelemetry.sdk.trace.SdkTracerProvider;
 import io.opentelemetry.sdk.trace.SdkTracerProviderBuilder;
 import java.time.Instant;
+import java.util.Objects;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentLinkedDeque;
 import java.util.concurrent.TimeUnit;
@@ -168,6 +169,7 @@ public InvocationOtelPlugin() {
      * @param config the plugin configuration
      */
     public InvocationOtelPlugin(SdkTracerProviderBuilder tracerProviderBuilder, OtelPluginConfig config) {
+        Objects.requireNonNull(config, "config must not be null");
         this.idGenerator = DeterministicIdGenerator.installOn(tracerProviderBuilder);
         // Wrap the configured sampler so durable spans use the execution's single precomputed decision.
         DurableSampler.installOn(tracerProviderBuilder);
@@ -189,6 +191,7 @@ public InvocationOtelPlugin(SdkTracerProviderBuilder tracerProviderBuilder, Otel
      * @param config the plugin configuration
      */
     public InvocationOtelPlugin(OtelPluginConfig config) {
+        Objects.requireNonNull(config, "config must not be null");
         this.contextExtractor = config.contextExtractor();
         this.enableMdc = config.enableMdc();
         this.workflowSpanName = config.workflowSpanName();

otel-plugin/src/test/java/software/amazon/lambda/durable/otel/OtelPluginConfigValidationTest.java

@@ -0,0 +1,43 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+package software.amazon.lambda.durable.otel;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.verifyNoInteractions;
+
+import io.opentelemetry.sdk.trace.SdkTracerProvider;
+import org.junit.jupiter.api.Test;
+
+class OtelPluginConfigValidationTest {
+
+    @Test
+    void configOnlyConstructorsRejectNullConfig() {
+        var invocationError =
+                assertThrows(NullPointerException.class, () -> new InvocationOtelPlugin((OtelPluginConfig) null));
+        var executionError =
+                assertThrows(NullPointerException.class, () -> new ExecutionOtelPlugin((OtelPluginConfig) null));
+
+        assertEquals("config must not be null", invocationError.getMessage());
+        assertEquals("config must not be null", executionError.getMessage());
+    }
+
+    @Test
+    void invocationConstructorRejectsNullConfigBeforeTouchingBuilder() {
+        var builder = spy(SdkTracerProvider.builder());
+
+        assertThrows(NullPointerException.class, () -> new InvocationOtelPlugin(builder, null));
+
+        verifyNoInteractions(builder);
+    }
+
+    @Test
+    void executionConstructorRejectsNullConfigBeforeTouchingBuilder() {
+        var builder = spy(SdkTracerProvider.builder());
+
+        assertThrows(NullPointerException.class, () -> new ExecutionOtelPlugin(builder, null));
+
+        verifyNoInteractions(builder);
+    }
+}