Add command to check if the hovered element is main method (#296)

* Add command to check if the hovered element is main method

Signed-off-by: Jinbo Wang <[email protected]>

* Make checkstyle happy

Signed-off-by: Jinbo Wang <[email protected]>

* Address review comments

Signed-off-by: Jinbo Wang <[email protected]>

Author: testforstephen

com.microsoft.java.debug.plugin/plugin.xml

@@ -13,6 +13,7 @@
             <command id="vscode.java.resolveMainMethod"/>
             <command id="vscode.java.inferLaunchCommandLength"/>
             <command id="vscode.java.checkProjectSettings"/>
+            <command id="vscode.java.resolveElementAtSelection"/>
        </delegateCommandHandler>
    </extension>
 </plugin>

com.microsoft.java.debug.plugin/src/main/java/com/microsoft/java/debug/plugin/internal/JavaDebugDelegateCommandHandler.java

@@ -31,6 +31,7 @@ public class JavaDebugDelegateCommandHandler implements IDelegateCommandHandler
     public static final String RESOLVE_MAINMETHOD = "vscode.java.resolveMainMethod";
     public static final String INFER_LAUNCH_COMMAND_LENGTH = "vscode.java.inferLaunchCommandLength";
     public static final String CHECK_PROJECT_SETTINGS = "vscode.java.checkProjectSettings";
+    public static final String RESOLVE_ELEMENT_AT_SELECTION = "vscode.java.resolveElementAtSelection";
 
     @Override
     public Object executeCommand(String commandId, List<Object> arguments, IProgressMonitor progress) throws Exception {
@@ -60,6 +61,8 @@ public Object executeCommand(String commandId, List<Object> arguments, IProgress
                 return LaunchCommandHandler.getLaunchCommandLength(JsonUtils.fromJson((String) arguments.get(0), LaunchArguments.class));
             case CHECK_PROJECT_SETTINGS:
                 return ProjectSettingsChecker.check(JsonUtils.fromJson((String) arguments.get(0), ProjectSettingsChecker.ProjectSettingsCheckerParams.class));
+            case RESOLVE_ELEMENT_AT_SELECTION:
+                return ResolveElementHandler.resolveElementAtSelection(arguments, progress);
             default:
                 break;
         }

com.microsoft.java.debug.plugin/src/main/java/com/microsoft/java/debug/plugin/internal/ResolveElementHandler.java

@@ -0,0 +1,73 @@
+/*******************************************************************************
+ * Copyright (c) 2019 Microsoft Corporation and others.
+ * 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
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     Microsoft Corporation - initial API and implementation
+ *******************************************************************************/
+
+package com.microsoft.java.debug.plugin.internal;
+
+import java.util.Collections;
+import java.util.List;
+
+import org.eclipse.core.runtime.IProgressMonitor;
+import org.eclipse.jdt.core.ICompilationUnit;
+import org.eclipse.jdt.core.IJavaElement;
+import org.eclipse.jdt.core.IMethod;
+import org.eclipse.jdt.core.IType;
+import org.eclipse.jdt.core.JavaModelException;
+import org.eclipse.jdt.ls.core.internal.JDTUtils;
+import org.eclipse.jdt.ls.core.internal.JavaLanguageServerPlugin;
+
+import com.microsoft.java.debug.core.DebugException;
+
+public class ResolveElementHandler {
+
+    /**
+     * Resolve the Java element at the selected position.
+     * @return the resolved Java element information.
+     */
+    public static Object resolveElementAtSelection(List<Object> arguments, IProgressMonitor monitor) throws DebugException {
+        if (arguments == null || arguments.size() < 3) {
+            return Collections.emptyList();
+        }
+
+        String uri = (String) arguments.get(0);
+        int line = (int) Math.round((double) arguments.get(1));
+        int column = (int) Math.round((double) arguments.get(2));
+        final ICompilationUnit unit = JDTUtils.resolveCompilationUnit(uri);
+        try {
+            IJavaElement element = JDTUtils.findElementAtSelection(unit, line, column,
+                    JavaLanguageServerPlugin.getPreferencesManager(), monitor);
+            if (element instanceof IMethod) {
+                return new JavaElement(((IMethod) element).getDeclaringType().getFullyQualifiedName(),
+                    element.getJavaProject().getProject().getName(),
+                    ((IMethod) element).isMainMethod());
+            } else if (element instanceof IType) {
+                return new JavaElement(((IType) element).getFullyQualifiedName(),
+                    element.getJavaProject().getProject().getName(),
+                    ResolveMainMethodHandler.getMainMethod((IType) element) != null);
+            }
+        } catch (JavaModelException e) {
+            throw new DebugException("Failed to resolve the selected element information: " + e.getMessage(), e);
+        }
+
+        return null;
+    }
+
+    static class JavaElement {
+        private String declaringType;
+        private String projectName;
+        private boolean hasMainMethod;
+
+        public JavaElement(String declaringType, String projectName, boolean hasMainMethod) {
+            this.declaringType = declaringType;
+            this.projectName = projectName;
+            this.hasMainMethod = hasMainMethod;
+        }
+    }
+}

com.microsoft.java.debug.plugin/src/main/java/com/microsoft/java/debug/plugin/internal/ResolveMainMethodHandler.java

@@ -95,7 +95,10 @@ private static List<IMethod> searchMainMethods(ICompilationUnit compilationUnit)
         return result;
     }
 
-    private static IMethod getMainMethod(IType type) throws JavaModelException {
+    /**
+     * Returns the main method defined in the type.
+     */
+    public static IMethod getMainMethod(IType type) throws JavaModelException {
         for (IMethod method : type.getMethods()) {
             // Have at most one main method in the member methods of the type.
             if (method.isMainMethod()) {