Fix: function calling not able to resolve input types

Resolves #726

spring-ai-core/src/main/java/org/springframework/ai/model/function/TypeResolverHelper.java

@@ -22,6 +22,8 @@ import java.util.function.Function;
 
 import net.jodah.typetools.TypeResolver;
 
+import org.springframework.cloud.function.context.catalog.FunctionTypeUtils;
+
 /**
  * @author Christian Tzolov
  */
@@ -58,6 +60,12 @@ public class TypeResolverHelper {
 	}
 
 	public static Type getFunctionArgumentType(Type functionType, int argumentIndex) {
+
+		// Resolves: https://github.com/spring-projects/spring-ai/issues/726
+		if (!(functionType instanceof ParameterizedType)) {
+			functionType = FunctionTypeUtils.discoverFunctionTypeFromClass(FunctionTypeUtils.getRawType(functionType));
+		}
+
 		var argumentType = functionType instanceof ParameterizedType
 				? ((ParameterizedType) functionType).getActualTypeArguments()[argumentIndex] : Object.class;
 
@@ -77,10 +85,4 @@ public class TypeResolverHelper {
 				: null;
 	}
 
-	// public static void main(String[] args) {
-	// Class<? extends Function<?, ?>> clazz = MockWeatherService.class;
-	// System.out.println(getFunctionInputType(clazz));
-
-	// }
-
 }

spring-ai-core/src/test/java/org/springframework/ai/model/function/StandaloneWeatherFunction.java

@@ -0,0 +1,34 @@
+/*
+ * Copyright 2024-2024 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.ai.model.function;
+
+import java.util.function.Function;
+
+import org.springframework.ai.model.function.TypeResolverHelperIT.WeatherRequest;
+import org.springframework.ai.model.function.TypeResolverHelperIT.WeatherResponse;
+
+/**
+ * @author Christian Tzolov
+ */
+public class StandaloneWeatherFunction implements Function<WeatherRequest, WeatherResponse> {
+
+	@Override
+	public WeatherResponse apply(WeatherRequest weatherRequest) {
+		return new WeatherResponse(42.0f);
+	}
+
+}

spring-ai-core/src/test/java/org/springframework/ai/model/function/TypeResolverHelperIT.java

@@ -0,0 +1,90 @@
+/*
+ * Copyright 2023 - 2024 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.ai.model.function;
+
+import java.lang.reflect.Type;
+import java.util.function.Function;
+
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.SpringBootConfiguration;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.cloud.function.context.config.FunctionContextUtils;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.support.GenericApplicationContext;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@SpringBootTest
+class TypeResolverHelperIT {
+
+	@Autowired
+	GenericApplicationContext applicationContext;
+
+	@ParameterizedTest(name = "{0} : {displayName} ")
+	@ValueSource(strings = { "weatherClassDefinition", "weatherFunctionDefinition", "standaloneWeatherFunction" })
+	void beanInputTypeResolutionTest(String beanName) {
+		assertThat(applicationContext).isNotNull();
+		Type beanType = FunctionContextUtils.findType(applicationContext.getBeanFactory(), beanName);
+		assertThat(beanType).isNotNull();
+		Type functionInputType = TypeResolverHelper.getFunctionArgumentType(beanType, 0);
+		assertThat(functionInputType).isNotNull();
+		assertThat(functionInputType.getTypeName()).isEqualTo(WeatherRequest.class.getName());
+
+	}
+
+	public record WeatherRequest(String city) {
+	}
+
+	public record WeatherResponse(float temperatureInCelsius) {
+	}
+
+	public static class Outer {
+
+		public static class InnerWeatherFunction implements Function<WeatherRequest, WeatherResponse> {
+
+			@Override
+			public WeatherResponse apply(WeatherRequest weatherRequest) {
+				return new WeatherResponse(42.0f);
+			}
+
+		}
+
+	}
+
+	@SpringBootConfiguration
+	public static class TypeResolverHelperConfiguration {
+
+		@Bean()
+		Outer.InnerWeatherFunction weatherClassDefinition() {
+			return new Outer.InnerWeatherFunction();
+		}
+
+		@Bean()
+		Function<WeatherRequest, WeatherResponse> weatherFunctionDefinition() {
+			return new Outer.InnerWeatherFunction();
+		}
+
+		@Bean()
+		StandaloneWeatherFunction standaloneWeatherFunction() {
+			return new StandaloneWeatherFunction();
+		}
+
+	}
+
+}