Add public registration method to bean post processor

Also simplifies logic of looking up message types

spring-cloud-function-context/src/main/java/org/springframework/cloud/function/context/ContextFunctionCatalogAutoConfiguration.java

@@ -318,6 +318,12 @@ public class ContextFunctionCatalogAutoConfiguration {
 			}
 		}
 
+		@SuppressWarnings("unchecked")
+		public <T> void register(FunctionRegistration<T> function) {
+			wrap((FunctionRegistration<Object>) function,
+					function.getNames().iterator().next());
+		}
+
 		public Set<FunctionRegistration<?>> merge(
 				Map<String, FunctionRegistration<?>> initial,
 				Map<String, Consumer<?>> consumers, Map<String, Supplier<?>> suppliers,
@@ -387,7 +393,7 @@ public class ContextFunctionCatalogAutoConfiguration {
 		private Collection<String> getAliases(String key) {
 			Collection<String> names = new LinkedHashSet<>();
 			String value = getQualifier(key);
-			if (value.equals(key)) {
+			if (value.equals(key) && registry != null) {
 				names.addAll(Arrays.asList(registry.getAliases(key)));
 			}
 			names.add(value);
@@ -416,7 +422,7 @@ public class ContextFunctionCatalogAutoConfiguration {
 		}
 
 		private String getQualifier(String key) {
-			if (registry.containsBeanDefinition(key)) {
+			if (registry != null && registry.containsBeanDefinition(key)) {
 				BeanDefinition beanDefinition = registry.getBeanDefinition(key);
 				Object source = beanDefinition.getSource();
 				if (source instanceof StandardMethodMetadata) {
@@ -658,16 +664,10 @@ public class ContextFunctionCatalogAutoConfiguration {
 		}
 
 		private boolean isMessage(Object function) {
-			String name = registrations.get(function);
+			return Message.class
-			if (name == null || !registry.containsBeanDefinition(name)) {
+					.isAssignableFrom(findType(function, ParamType.INPUT_INNER_WRAPPER))
-				return false;
+					|| Message.class.isAssignableFrom(
-			}
+							findType(function, ParamType.OUTPUT_INNER_WRAPPER));
-			return Message.class.isAssignableFrom(findType(name,
-					(AbstractBeanDefinition) registry.getBeanDefinition(name),
-					ParamType.INPUT_INNER_WRAPPER))
-					|| Message.class.isAssignableFrom(findType(name,
-							(AbstractBeanDefinition) registry.getBeanDefinition(name),
-							ParamType.OUTPUT_INNER_WRAPPER));
 		}
 
 		private Class<?> findType(Object function, ParamType type) {
@@ -678,7 +678,8 @@ public class ContextFunctionCatalogAutoConfiguration {
 					return values.get(type);
 				}
 			}
-			if (name == null || !registry.containsBeanDefinition(name)) {
+			if (name == null || registry == null
+					|| !registry.containsBeanDefinition(name)) {
 				if (function != null) {
 					Type param = findTypeFromBeanClass(function.getClass(), type);
 					if (param != null) {

spring-cloud-function-context/src/test/java/org/springframework/cloud/function/context/ContextFunctionPostProcessorTests.java

@@ -0,0 +1,97 @@
+/*
+ * Copyright 2016-2017 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
+ *
+ *      http://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.function.context;
+
+import java.util.Collections;
+import java.util.function.Function;
+
+import org.junit.Test;
+
+import org.springframework.cloud.function.context.ContextFunctionCatalogAutoConfiguration.ContextFunctionPostProcessor;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import reactor.core.publisher.Flux;
+
+/**
+ * @author Dave Syer
+ *
+ */
+public class ContextFunctionPostProcessorTests {
+
+	private ContextFunctionPostProcessor processor = new ContextFunctionPostProcessor();
+
+	@Test
+	public void basicRegistrationFeatures() {
+		processor.register(new FunctionRegistration<>(new Foos()).names("foos"));
+		@SuppressWarnings("unchecked")
+		Function<Flux<Integer>, Flux<String>> foos = (Function<Flux<Integer>, Flux<String>>) processor
+				.compose("foos");
+		assertThat(foos.apply(Flux.just(2)).blockFirst()).isEqualTo("4");
+	}
+
+	@Test
+	public void registrationThroughMerge() {
+		FunctionRegistration<Foos> registration = new FunctionRegistration<>(new Foos())
+				.names("foos");
+		processor.merge(Collections.singletonMap("foos", registration),
+				Collections.emptyMap(), Collections.emptyMap(), Collections.emptyMap());
+		@SuppressWarnings("unchecked")
+		Function<Flux<Integer>, Flux<String>> foos = (Function<Flux<Integer>, Flux<String>>) processor
+				.compose("foos");
+		assertThat(foos.apply(Flux.just(2)).blockFirst()).isEqualTo("4");
+	}
+
+	@Test
+	public void registrationThroughMergeFromNamedFunction() {
+		processor.merge(Collections.emptyMap(), Collections.emptyMap(),
+				Collections.emptyMap(), Collections.singletonMap("foos", new Foos()));
+		@SuppressWarnings("unchecked")
+		Function<Flux<Integer>, Flux<String>> foos = (Function<Flux<Integer>, Flux<String>>) processor
+				.compose("foos");
+		assertThat(foos.apply(Flux.just(2)).blockFirst()).isEqualTo("4");
+	}
+
+	@Test
+	public void compose() {
+		processor.register(new FunctionRegistration<>(new Foos()).names("foos"));
+		processor.register(new FunctionRegistration<>(new Bars()).names("bars"));
+		@SuppressWarnings("unchecked")
+		Function<Flux<Integer>, Flux<String>> foos = (Function<Flux<Integer>, Flux<String>>) processor
+				.compose("foos,bars");
+		assertThat(foos.apply(Flux.just(2)).blockFirst()).isEqualTo("Hello 4");
+	}
+
+	protected static class Foos implements Function<Integer, String> {
+
+		@Override
+		public String apply(Integer t) {
+			return "" + 2 * t;
+		}
+
+	}
+
+	protected static class Bars implements Function<String, String> {
+
+		@Override
+		public String apply(String t) {
+			return "Hello " + t;
+		}
+
+	}
+
+}