Creating a plugin page hack

After hours seeking through the WordPress sources it I was unable to find ANY resonable method of creating a front end page from a plugin. My goal was simple, I wanted http://mysite.com/friends to show a page generated by my plugin. This is a multi-site installation and I do not want blog owners to be able to eliminate this page. My final implementation doesn’t involve users blogs but it could.

wp-includes/theme.php: I added this function

function get_extension_page_template() {
    $page = get_queried_object();
    $templates = array($page->ID.'.php');
    return get_query_template($page->ID,$templates);
}

wp-includes/template-loader.php: I added this just ofter the if(is_404() line(near line 8)
elseif ( is_extension_page() && $template = get_extension_page_template()) :

wp-includes/query.php: I added two functions

function set_extension_page($page,$object) {
    global $wp_query;
    return $wp_query->set_extension_page($page,$object);
}

function is_extension_page() {
  global $wp_query;
	return $wp_query->is_extension_page();
}

wp-includes/query.php: I added two properties to the WP_Query class

var $extension_page = null;
  var $extension_page_object = null;

wp-includes/query.php: I added two methods to the WP_Query class

function set_extension_page($page,$object) {
      $this->extension_page_object = $object;
      $this->extension_page = $page;
  }
  function is_extension_page() {
     return isset($this->extension_page);
  }

wp-includes/query.php: I changed the get_queried_object method in the WP_Query class

function get_queried_object() {
		if ( isset($this->queried_object) )
			return $this->queried_object;

    if (isset($this->extension_page_object)) {
        return $this->extension_page_object;
    }
		$this->queried_object = NULL;
		$this->queried_object_id = 0;

		if ( $this->is_category || $this->is_tag || $this->is_tax ) {
			$tax_query_in_and = wp_list_filter( $this->tax_query->queries, array( 'operator' => 'NOT IN' ), 'NOT' );

			$query = reset( $tax_query_in_and );

			if ( 'term_id' == $query['field'] )
				$term = get_term( reset( $query['terms'] ), $query['taxonomy'] );
			else
				$term = get_term_by( $query['field'], reset( $query['terms'] ), $query['taxonomy'] );

			if ( $term && ! is_wp_error($term) )  {
				$this->queried_object = $term;
				$this->queried_object_id = (int) $term->term_id;

				if ( $this->is_category )
					_make_cat_compat( $this->queried_object );
			}
		} elseif ( $this->is_post_type_archive ) {
			$this->queried_object = get_post_type_object( $this->get('post_type') );
		} elseif ( $this->is_posts_page ) {
			$page_for_posts = get_option('page_for_posts');
			$this->queried_object = & get_page( $page_for_posts );
			$this->queried_object_id = (int) $this->queried_object->ID;
		} elseif ( $this->is_singular && !is_null($this->post) ) {
			$this->queried_object = $this->post;
			$this->queried_object_id = (int) $this->post->ID;
		} elseif ( $this->is_author ) {
			$this->queried_object_id = (int) $this->get('author');
			$this->queried_object = get_userdata( $this->queried_object_id );
		}

		return $this->queried_object;
	}

wp-includes/class-wp.php: I changed the handle_404 method to the following

function handle_404() {
		global $wp_query;

		if ( !is_admin() && ( 0 == count( $wp_query->posts ) ) && !is_404() && !is_robots() && !is_search() && !is_home() ) {
			// Don't 404 for these queries if they matched an object.
			if ( ( is_extension_page() || is_tag() || is_category() || is_tax() || is_author() || is_post_type_archive() ) && $wp_query->get_queried_object() && !is_paged() ) {
				if ( !is_404() )
					status_header( 200 );
				return;
			}

			$wp_query->set_404();
			status_header( 404 );
			nocache_headers();
		} elseif ( !is_404() ) {
			status_header( 200 );
		}
	}

The final result is that I can create an object in plugins on patched sites and test for certain conditions, such as $blogpage = $this->ID and then call set_extension_page($this->ID,$this); to register the page to be displayed. The theme must also have a template setup for that plugin which is named (first parameter of set_extension_page).php but its better than nothing.

I admit this is just an ugly hack, but it works. It would be nice to see a feature like this added to wordpress in the future.