Fix for https://github.com/spring-projects/sts4/issues/404

... with regression test.

headless-services/commons/commons-java/src/main/java/org/springframework/ide/vscode/commons/jandex/MethodImpl.java

@@ -11,6 +11,7 @@
 
 package org.springframework.ide.vscode.commons.jandex;
 
+import java.util.List;
 import java.util.stream.Stream;
 
 import org.jboss.jandex.MethodInfo;
@@ -23,6 +24,12 @@ import org.springframework.ide.vscode.commons.javadoc.IJavadoc;
 
 public class MethodImpl implements IMethod {
 
+	/**
+	 * Test code may set this to manually inject test data to make up for some missing 
+	 * capabilities of Jandex (e.g. discovering the names of method parameters).
+	 */
+	public static TestDataProvider testDataProvider = null;
+
 	private static final String JANDEX_CONTRUCTOR_NAME = "<init>";
 
 	private IType declaringType;
@@ -109,4 +116,13 @@ public class MethodImpl implements IMethod {
 		return method.toString();
 	}
 
+	@Override
+	public List<String> getParameterNames() {
+		if (testDataProvider!=null) {
+			return testDataProvider.getParameterNames(this);
+		} else {
+			throw new UnsupportedOperationException("Not supported with jandex");
+		}
+	}
+
 }

headless-services/commons/commons-java/src/main/java/org/springframework/ide/vscode/commons/jandex/TestDataProvider.java

@@ -0,0 +1,37 @@
+/*******************************************************************************
+ * Copyright (c) 2020 Pivotal, Inc.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * https://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     Pivotal, Inc. - initial API and implementation
+ *******************************************************************************/
+package org.springframework.ide.vscode.commons.jandex;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import org.springframework.ide.vscode.commons.java.IMethod;
+import org.springframework.ide.vscode.commons.util.Assert;
+
+import com.google.common.collect.ImmutableList;
+
+public class TestDataProvider {
+
+	private Map<String, List<String>> methodParameters = new HashMap<>();
+	
+	public List<String> getParameterNames(IMethod method) {
+		String key = method.getBindingKey();
+		List<String> l = methodParameters.get(method.getBindingKey());
+		Assert.isLegal(l!=null, "Test code should provide method parameter names for '"+key+"'");;
+		return l;
+	}
+
+	public void methodParams(String bindingKey, String... names) {
+		methodParameters.put(bindingKey, ImmutableList.copyOf(names));
+	}
+
+}

headless-services/commons/commons-java/src/main/java/org/springframework/ide/vscode/commons/java/IMethod.java

@@ -12,6 +12,7 @@
  *******************************************************************************/
 package org.springframework.ide.vscode.commons.java;
 
+import java.util.List;
 import java.util.stream.Stream;
 
 public interface IMethod extends IMember {
@@ -71,4 +72,6 @@ public interface IMethod extends IMember {
 		return getDeclaringType().classpathContainer();
 	}
 
+	List<String> getParameterNames();
+
 }

headless-services/commons/commons-java/src/main/java/org/springframework/ide/vscode/commons/jdtls/Wrappers.java

@@ -333,6 +333,11 @@ public class Wrappers {
 				return data.isConstructor();
 			}
 
+			@Override
+			public List<String> getParameterNames() {
+				return data.getParameterNames();
+			}
+
 		};
 	}