Bug 80833 [Import/Export] Import exisiting should pre-check for project already in workspace
While it is good that it lets you import projects in the default workspace location, it should not let you select projects that already exist in the workspace (since importing such a project will fail). When searching for .project files in the file system, it could use IWorkspaceRoot.findFilesForLocation followed by checking IFile.exists() to filter out .project files for existing projects.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/wizards/datatransfer/WizardProjectsImportPage.java
private IProject[] wsProjects;
	
	private static final String[] FILE_IMPORT_MASK = {
			"*.jar;*.zip;*.tar;*.tar.gz;*.tgz", "*.*" }; 
	
	private String lastPath;
	/**
	 * Creates a new project creation wizard page.
	 * 
	 */
	public WizardProjectsImportPage() {
		this("wizardExternalProjectsPage"); 
	}
	/**
	 * Create a new instance of the receiver.
	 * 
	 * @param pageName
	 */
	public WizardProjectsImportPage(String pageName) {
		super(pageName);
		setPageComplete(false);
		setTitle(DataTransferMessages.WizardProjectsImportPage_ImportProjectsTitle);
		setDescription(DataTransferMessages.WizardProjectsImportPage_ImportProjectsDescription);
	}
	/**
	 * Create a new instance of the receiver.
	 * 
	 * @param pageName
	 * @param title
	 * @param titleImage