GH-1236 Fix actuator's FunctionsEndpoint to handle ineligible functions

Given that we have ineligible function catalog.lookup(..) may return null if function is ineligible.

Resolves #1236

Author: olegz

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

@@ -50,24 +50,25 @@ public Map<String, Map<String, Object>> listAll() {
 		Set<String> names = functionCatalog.getNames(null);
 		for (String name : names) {
 			FunctionInvocationWrapper function = functionCatalog.lookup(name);
-			Map<String, Object> functionMap = new LinkedHashMap<>();
-			if (function.isFunction()) {
-				functionMap.put("type", "FUNCTION");
-				functionMap.put("input-type", this.toSimplePolyIn(function));
-				functionMap.put("output-type", this.toSimplePolyOut(function));
+			if (function != null) {
+				Map<String, Object> functionMap = new LinkedHashMap<>();
+				if (function.isFunction()) {
+					functionMap.put("type", "FUNCTION");
+					functionMap.put("input-type", this.toSimplePolyIn(function));
+					functionMap.put("output-type", this.toSimplePolyOut(function));
+				}
+				else if (function.isConsumer()) {
+					functionMap.put("type", "CONSUMER");
+					functionMap.put("input-type", this.toSimplePolyIn(function));
+				}
+				else {
+					functionMap.put("type", "SUPPLIER");
+					functionMap.put("output-type", this.toSimplePolyOut(function));
+				}
+				allFunctions.put(name, functionMap);
 			}
-			else if (function.isConsumer()) {
-				functionMap.put("type", "CONSUMER");
-				functionMap.put("input-type", this.toSimplePolyIn(function));
-			}
-			else {
-				functionMap.put("type", "SUPPLIER");
-				functionMap.put("output-type", this.toSimplePolyOut(function));
-			}
-			allFunctions.put(name, functionMap);
 		}
 
-
 		return allFunctions;
 	}
 

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

@@ -0,0 +1,74 @@
+/*
+ * Copyright 2021-2025 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.function.actuator;
+
+import java.util.Locale;
+import java.util.Map;
+import java.util.function.Function;
+
+import org.junit.jupiter.api.Test;
+
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.builder.SpringApplicationBuilder;
+import org.springframework.cloud.function.context.FunctionCatalog;
+import org.springframework.context.ApplicationContext;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ *
+ * @author Oleg Zhurakousky
+ */
+
+public class FunctionsEndpointTests {
+
+	@Test
+	public void ensureIneligibleFunctionWontCauseNPE() {
+		ApplicationContext context = new SpringApplicationBuilder(SampleConfiguration.class)
+				.run("--spring.cloud.function.ineligible-definitions=echo,uppercase",
+						"--spring.main.lazy-initialization=true");
+		FunctionCatalog catalog = context.getBean(FunctionCatalog.class);
+		FunctionsEndpoint endpoint = new FunctionsEndpoint(catalog);
+		Map<String, Map<String, Object>> allFunctionsinCatalog = endpoint.listAll();
+		// implicit assertion - no NPE
+		assertThat(allFunctionsinCatalog.size()).isEqualTo(2);
+		assertThat(allFunctionsinCatalog.containsKey("functionRouter"));
+		assertThat(allFunctionsinCatalog.containsKey("reverse"));
+	}
+
+	@EnableAutoConfiguration
+	@Configuration
+	public static class SampleConfiguration {
+
+		@Bean
+		public Function<String, String> echo() {
+			return v -> v;
+		}
+
+		@Bean
+		public Function<String, String> uppercase() {
+			return v -> v.toUpperCase(Locale.ROOT);
+		}
+
+		@Bean
+		public Function<String, String> reverse() {
+			return v -> new StringBuilder(v).reverse().toString();
+		}
+	}
+}