Add command for running checkstyle

This adds a command for the already existing action to run checkstyle on
the selected resources. That way users can invoke the command also via
Ctrl-3 quick assist or via a key binding.

There is no default key binding, as the normal workflow for users is to
rely on the Eclipse builder and to not invoke this command manually.

fixes #99

Author: Bananeweizen

net.sf.eclipsecs.ui/plugin.xml

@@ -308,7 +308,13 @@
         point="org.eclipse.ui.commands">
         <category id="net.sf.eclipsecs.ui" name="%commands.category.name"/>
         <command
-            categoryId="org.eclipse.jdt.ui.category.source"
+            categoryId="net.sf.eclipsecs.ui"
+            description="%CheckSelectedFilesAction.tooltip"
+            id="CheckstylePlugin.CheckSelectedFiles"
+            name="%CheckSelectedFilesAction.label"
+            defaultHandler="net.sf.eclipsecs.ui.actions.CheckSelectedFilesAction"/>
+        <command
+            categoryId="net.sf.eclipsecs.ui"
             description="%FixCheckstyleMarkersAction.tooltip"
             id="CheckstylePlugin.ApplyCheckstyleFixes"
             name="%FixCheckstyleMarkersAction.label"
@@ -326,7 +332,8 @@
             sequence="M1+M3+C"
             commandId="CheckstylePlugin.ApplyCheckstyleFixes"
             schemeId="org.eclipse.ui.defaultAcceleratorConfiguration"
-            contextId="org.eclipse.jdt.ui.javaEditorScope"/>></extension>
+            contextId="org.eclipse.jdt.ui.javaEditorScope"/>
+    </extension>
 
     <!-- Popupmenu action for the 'Configure Project(s) from blueprint...' action -->
     <extension
@@ -535,6 +542,10 @@
              commandId="CheckstylePlugin.PurgeCaches"
              icon="platform:/plugin/org.eclipse.ui/icons/full/etool16/clear.png">
        </image>
+       <image
+             commandId="CheckstylePlugin.CheckSelectedFiles"
+             icon="icons/checkstyle_command.png">
+       </image>
     </extension>
     <extension
           point="net.sf.eclipsecs.ui.quickfix">

net.sf.eclipsecs.ui/src/net/sf/eclipsecs/ui/actions/CheckSelectedFilesAction.java

@@ -22,27 +22,34 @@
 
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.HashSet;
 import java.util.List;
+import java.util.Set;
 
+import org.eclipse.core.commands.AbstractHandler;
+import org.eclipse.core.commands.ExecutionEvent;
+import org.eclipse.core.commands.ExecutionException;
 import org.eclipse.core.resources.IContainer;
 import org.eclipse.core.resources.IFile;
 import org.eclipse.core.resources.IResource;
 import org.eclipse.core.runtime.CoreException;
+import org.eclipse.core.runtime.IAdaptable;
 import org.eclipse.jface.action.IAction;
 import org.eclipse.jface.viewers.ISelection;
 import org.eclipse.jface.viewers.IStructuredSelection;
 import org.eclipse.ui.IObjectActionDelegate;
 import org.eclipse.ui.IWorkbenchPart;
+import org.eclipse.ui.handlers.HandlerUtil;
 
 import net.sf.eclipsecs.core.jobs.RunCheckstyleOnFilesJob;
 import net.sf.eclipsecs.ui.CheckstyleUIPlugin;
 
 /**
- * Action to diable Checkstyle on one ore more projects.
+ * Action to run Checkstyle on one ore more projects.
  *
  * @author Lars Ködderitzsch
  */
-public class CheckSelectedFilesAction implements IObjectActionDelegate {
+public class CheckSelectedFilesAction extends AbstractHandler implements IObjectActionDelegate {
 
   private IWorkbenchPart mPart;
 
@@ -62,13 +69,26 @@ public void selectionChanged(IAction action, ISelection selection) {
   }
 
   @Override
-  @SuppressWarnings("unchecked")
   public void run(IAction action) {
+    checkSelection(mSelection);
+  }
 
+  private void checkSelection(IStructuredSelection selection) {
+    Set<IResource> resources = new HashSet<>();
+    for (Object object : selection.toList()) {
+      if (object instanceof IAdaptable adaptable) {
+        var resource = adaptable.getAdapter(IResource.class);
+        if (resource != null) {
+          resources.add(resource);
+        }
+      }
+    }
     List<IFile> filesToCheck = new ArrayList<>();
-
     try {
-      addFileResources(mSelection.toList(), filesToCheck);
+      addFileResources(List.copyOf(resources), filesToCheck);
+      if (filesToCheck.isEmpty()) {
+        return;
+      }
 
       RunCheckstyleOnFilesJob job = new RunCheckstyleOnFilesJob(filesToCheck);
       job.setRule(job);
@@ -79,18 +99,16 @@ public void run(IAction action) {
   }
 
   /**
-   * Recursively add all files contained in the given resource collection to the
-   * second list.
+   * Recursively add all files contained in the given resource collection to the second list.
    *
    * @param resources
    *          list of resource
    * @param files
    *          the list of files
    * @throws CoreException
-   *           en unexpected exception
+   *           an unexpected exception
    */
   private void addFileResources(List<IResource> resources, List<IFile> files) throws CoreException {
-
     for (IResource resource : resources) {
 
       if (!resource.isAccessible()) {
@@ -104,4 +122,13 @@ private void addFileResources(List<IResource> resources, List<IFile> files) thro
       }
     }
   }
+
+  @Override
+  public Object execute(ExecutionEvent event) throws ExecutionException {
+    var selection = HandlerUtil.getCurrentSelection(event);
+    if (selection instanceof IStructuredSelection structuredSelection) {
+      checkSelection(structuredSelection);
+    }
+    return null;
+  }
 }