GH-1823 Make FunctionConfiguration conditional

Resolves #1823

spring-cloud-stream/src/main/java/org/springframework/cloud/stream/function/FunctionConfiguration.java

@@ -43,11 +43,13 @@ import org.springframework.beans.BeansException;
 import org.springframework.beans.factory.InitializingBean;
 import org.springframework.beans.factory.support.BeanDefinitionRegistry;
 import org.springframework.beans.factory.support.RootBeanDefinition;
+import org.springframework.boot.autoconfigure.AutoConfigureAfter;
 import org.springframework.boot.autoconfigure.AutoConfigureBefore;
-import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.cloud.function.context.FunctionCatalog;
 import org.springframework.cloud.function.context.FunctionProperties;
+import org.springframework.cloud.function.context.FunctionRegistry;
 import org.springframework.cloud.function.context.PollableBean;
 import org.springframework.cloud.function.context.catalog.BeanFactoryAwareFunctionRegistry.FunctionInvocationWrapper;
 import org.springframework.cloud.function.context.catalog.FunctionInspector;
@@ -105,9 +107,10 @@ import org.springframework.util.StringUtils;
  */
 @Configuration
 @EnableConfigurationProperties(StreamFunctionProperties.class)
-@AutoConfigureBefore(BindingServiceConfiguration.class)
 @Import({ BindingBeansRegistrar.class, BinderFactoryAutoConfiguration.class })
-@ConditionalOnClass(ContextFunctionCatalogAutoConfiguration.class)
+@AutoConfigureBefore(BindingServiceConfiguration.class)
+@AutoConfigureAfter(ContextFunctionCatalogAutoConfiguration.class)
+@ConditionalOnBean(FunctionRegistry.class)
 public class FunctionConfiguration {
 
 	@Bean

spring-cloud-stream/src/test/java/org/springframework/cloud/stream/function/ImplicitFunctionBindingTests.java

@@ -28,6 +28,7 @@ import reactor.core.publisher.Flux;
 import org.springframework.boot.WebApplicationType;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.builder.SpringApplicationBuilder;
+import org.springframework.cloud.function.context.config.ContextFunctionCatalogAutoConfiguration;
 import org.springframework.cloud.stream.annotation.EnableBinding;
 import org.springframework.cloud.stream.annotation.StreamListener;
 import org.springframework.cloud.stream.binder.test.InputDestination;
@@ -332,6 +333,26 @@ public class ImplicitFunctionBindingTests {
 		}
 	}
 
+
+	@Test
+	public void testNoFunctionEnabledConfiguration() {
+		System.clearProperty("spring.cloud.stream.function.definition");
+		try (ConfigurableApplicationContext context = new SpringApplicationBuilder(
+				TestChannelBinderConfiguration.getCompleteConfiguration(NoFunctionEnabledConfiguration.class))
+						.web(WebApplicationType.NONE).run("--spring.jmx.enabled=false")) {
+
+			try {
+				context.getBean(FunctionConfiguration.class);
+				fail();
+			}
+			catch (Exception e) {
+				// ignore
+			}
+
+		}
+	}
+
+
 	@EnableAutoConfiguration
 	public static class NoEnableBindingConfiguration  {
 
@@ -447,4 +468,13 @@ public class ImplicitFunctionBindingTests {
 		}
 	}
 
+	@EnableAutoConfiguration(exclude = ContextFunctionCatalogAutoConfiguration.class)
+	public static class NoFunctionEnabledConfiguration {
+
+		@Bean
+		public Supplier<String> supplier() {
+			return () -> "hello";
+		}
+	}
+
 }