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
public void setVisible(boolean visible) {
        super.setVisible(visible);
        if (visible && this.projectFromDirectoryRadio.getSelection()) {
        	this.directoryPathField.setFocus();
        } 
        if (visible && this.projectFromArchiveRadio.getSelection()) {
        	this.archivePathField.setFocus();
        }  
    }
	/**
	 * Update the list of projects based on path.
	 * Method declared public only for test suite.
	 * 
	 * @param path
	 */
	public void updateProjectsList(final String path) {
		
		if(path.equals(lastPath))
			return;
		
		lastPath = path;
		
		
		if (path == null || path.length() == 0) {
			selectedProjects = new ProjectRecord[0];
			projectsList.refresh(true);
			projectsList.setCheckedElements(selectedProjects);
			setPageComplete(selectedProjects.length > 0);
			return;
		}