fix #2023, add parent in the new TraceFeignContext (#2024)

fixes gh-2023

spring-cloud-sleuth-instrumentation/src/main/java/org/springframework/cloud/sleuth/instrument/web/client/feign/FeignContextBeanPostProcessor.java

@@ -43,7 +43,10 @@ public class FeignContextBeanPostProcessor implements BeanPostProcessor {
 	@Override
 	public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
 		if (bean instanceof FeignContext && !(bean instanceof TraceFeignContext)) {
-			return new TraceFeignContext(traceFeignObjectWrapper(), (FeignContext) bean);
+			FeignContext feignContext = (FeignContext) bean;
+			TraceFeignContext traceFeignContext = new TraceFeignContext(traceFeignObjectWrapper(), feignContext);
+			traceFeignContext.setApplicationContext(feignContext.getParent());
+			return traceFeignContext;
 		}
 		return bean;
 	}

spring-cloud-sleuth-instrumentation/src/test/java/org/springframework/cloud/sleuth/instrument/web/client/feign/FeignContextBeanPostProcessorTest.java

@@ -0,0 +1,52 @@
+/*
+ * Copyright 2013-2021 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.cloud.sleuth.instrument.web.client.feign;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+import org.springframework.beans.factory.BeanFactory;
+import org.springframework.cloud.openfeign.FeignContext;
+import org.springframework.context.ApplicationContext;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * @author Hash Jang
+ */
+@ExtendWith(MockitoExtension.class)
+class FeignContextBeanPostProcessorTest {
+
+    @Mock
+    BeanFactory beanFactory;
+
+    @Mock
+    ApplicationContext parent;
+
+    @Test
+    void should_pass_feign_application_context_to_the_trace_representation() {
+        FeignContextBeanPostProcessor feignContextBeanPostProcessor = new FeignContextBeanPostProcessor(beanFactory);
+        FeignContext feignContext = new FeignContext();
+        feignContext.setApplicationContext(parent);
+        TraceFeignContext traceFeignContext = (TraceFeignContext) feignContextBeanPostProcessor.postProcessAfterInitialization(feignContext, "test");
+        assertThat(traceFeignContext.getParent()).isNotNull();
+        assertThat(traceFeignContext.getParent()).isSameAs(parent);
+    }
+
+}