DATACMNS-1518 - Fixed detection of varargs overloads for SpEL expressions.

Before this commit we haven't properly resolved methods on a root object provided by an EvaluationContextExtension that was using varargs. With a vararg method, the number of parameters handed into the method is not necessary equal to the number of parameters. We previously simply skipped methods with a different number of arguments. We now try direct matches first but calculate valid varargs alternatives in case that initial lookup fails and try to match those alternatives.

This lookup is implemented in ….util.ParameterTypes now and used by ….spel.spi.Function. The latter now also handles the actual invocation of those methods properly by collecting the trailing arguments into an array.

src/test/java/org/springframework/data/spel/spi/FunctionUnitTests.java

@@ -0,0 +1,68 @@
+/*
+ * Copyright 2019 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.data.spel.spi;
+
+import static org.assertj.core.api.Assertions.*;
+
+import java.lang.reflect.Method;
+import java.util.Arrays;
+
+import org.junit.Test;
+import org.springframework.core.convert.TypeDescriptor;
+import org.springframework.util.ReflectionUtils;
+
+/**
+ * Unit tests for {@link Function}.
+ *
+ * @author Oliver Drotbohm
+ */
+public class FunctionUnitTests {
+
+	@Test // DATACMNS-1518
+	public void detectsVarArgsOverload() {
+
+		Method method = ReflectionUtils.findMethod(Sample.class, "someMethod", String[].class);
+
+		Function function = new Function(method, new Sample());
+
+		TypeDescriptor stringDescriptor = TypeDescriptor.valueOf(String.class);
+
+		assertThat(function.supports(Arrays.asList(stringDescriptor, stringDescriptor))).isTrue();
+	}
+
+	@Test // DATACMNS-1518
+	public void detectsObjectVarArgsOverload() {
+
+		Method method = ReflectionUtils.findMethod(Sample.class, "onePlusObjectVarargs", String.class, Object[].class);
+
+		Function function = new Function(method, new Sample());
+
+		TypeDescriptor stringDescriptor = TypeDescriptor.valueOf(String.class);
+
+		assertThat(function.supports(Arrays.asList(stringDescriptor, stringDescriptor))).isTrue();
+	}
+
+	class Sample {
+
+		String someMethod(String... args) {
+			return "result";
+		}
+
+		String onePlusObjectVarargs(String string, Object... args) {
+			return null;
+		}
+	}
+}