WordPress plugin that allow user to “edit_others_posts” to save only, not publish

## wpse161061.php
<?php
/**
 * Plugin Name: WPSE 161061
 * Description: Allow user to “edit_others_posts” to save only, not publish
 * Plugin URI: http://wordpress.stackexchange.com/questions/161061/
 * Author: Giuseppe Mazzapica
 * Author URI: http://gm.zoomlab.it
 * License: GPLv3
 * Version: 1.0.0
 *
 */

/*
Copyright (C) 2014 Giuseppe Mazzapica

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.

*/

class CustomEditorRole {

  private static $role = 'authorplus';
  private $role_label;

  function __construct() {
    // here we need a real, loaded, text domain
    $this->role_label = __( 'Author +', 'yout-txt-dmn' );
  }

  function addRole() {
    global $wp_roles;
    if ( ! $wp_roles instanceof WP_Roles ) {
      $wp_roles = new WP_Roles;
    }
    $author = get_role( 'author' );
    $caps = $author->capabilities; // start with author capabilities
    $caps['publish_posts'] = FALSE;
    $caps['edit_published_posts'] = FALSE;
    $caps['delete_published_posts'] = FALSE;
    $caps['edit_others_pending_posts'] = TRUE; // custom cap
    // create new role with custom caps
    add_role( self::$role, $this->role_label, $caps );
  }

  function removeRole() {
    global $wp_roles;
    if ( ! $wp_roles instanceof WP_Roles ) {
      $wp_roles = new WP_Roles;
    }
    remove_role(self::$role);
  }

}

class CustomEditorCaps {

  function manageCaps( $allcaps, $caps, $args, $user ) {
    if ( ! $this->shouldManage( $args[0], $user ) ) {
      return $allcaps;
    }
    // Are we saving?
    $action = filter_input( INPUT_POST, 'action', FILTER_SANITIZE_STRING );
    $method = strtoupper(filter_var($_SERVER['REQUEST_METHOD'], FILTER_SANITIZE_STRING ));
    if ( $method !== 'POST' ) { // not saving
      global $pagenow;
      // we are interested only on post list and  post edit screens
      if (
        is_admin()
        && in_array( $pagenow, array( 'post.php', 'post-new.php', 'edit.php' ), TRUE
      ) ) {
        $screen_id = $pagenow === 'edit.php' ? 'edit-post' : 'post';
        $allcaps = $this->maybeAllow( $args, $allcaps, $user, $screen_id );
      }
    } elseif ( $action === 'editpost' ) { // saving and right action
      $allcaps = $this->maybeAllowOnSave( $args, $allcaps, $user  );
    }
    return $allcaps; // always return: it's a filter
  }

  function allowPreview( $posts, $query ) {
    if ( is_admin()
      || ! $query->is_main_query()
      || empty( $posts )
      || ! $query->is_single
      || $posts[0]->post_type !== 'post'
    ) {
      return $posts; // return first argument: it's a filter
    }
    $status = get_post_status( $posts[0] );
    $post_status_obj = get_post_status_object( $status );
    if (
      ! $post_status_obj->public
      && $status === 'pending'
      && current_user_can('edit_others_pending_posts')
    ) {
      // post is pending and our user has our special role
      // allow preview
      global $wp_post_statuses;
      $wp_post_statuses[$status]->public = TRUE;
    }
    return $posts; // return first argument: it's a filter
  }

  private function maybeAllow( $args, $allcaps, $user, $screen ) {
    if ( $args[0] === 'edit_others_posts' ) {
      // if filtering 'edit_others_posts' we have no access to single post data
      // allow cap only on post list screen and before querying posts
      $allcaps['edit_others_posts'] = ! did_action('pre_get_posts')
        && $screen === 'edit-post';
      return $allcaps;
    }
    $post = get_post( $args[2] );
    if (  $post->post_status === 'pending' ) {
      $allcaps['edit_others_posts'] = TRUE;
    }
    return $allcaps; // always return: it's a filter
  }

  private function maybeAllowOnSave( $args, $allcaps, $user ) {
    $data = $this->getPostedData();
    if ( $data['post_type'] !== 'post' || (int) $data['post_ID'] <= 0 ) {
      return $allcaps;
    }
    $post = get_post( $data['post_ID'] );
    if (
      $post->post_status === 'pending'
      && $data['original_post_status'] === 'pending'
      && ( empty( $data['post_status'] ) || $data['post_status'] === 'pending' )
    ) {
      // if post is pending and will stay pending allow editing
      $allcaps['edit_others_posts'] = true;
    }
    return $allcaps;
  }

  private function shouldManage( $cap, $user ) {
    return is_admin() // not affect frontend
      && in_array( $cap, array( 'edit_others_posts', 'edit_post' ), TRUE )
      && ! $user->has_cap( 'delete_others_posts' ) // real editor or more
      && $user->has_cap( 'edit_others_pending_posts' ) // our role
      && ! defined( 'DOING_AJAX' ); // does not affect ajax
  }

  private function getPostedData() {
    return filter_input_array( INPUT_POST, array(
      'post_type'            => FILTER_SANITIZE_STRING,
      'post_ID'              => FILTER_SANITIZE_NUMBER_INT,
      'original_post_status' => FILTER_SANITIZE_STRING,
      'post_status'          => FILTER_SANITIZE_STRING,
    ) );
  }

}


register_activation_hook( __FILE__, array( new CustomEditorRole, 'addRole' ) );
register_deactivation_hook( __FILE__, array( new CustomEditorRole, 'removeRole' ) );
$cap_manager = new CustomEditorCaps;
add_filter( 'user_has_cap', array( $cap_manager, 'manageCaps' ), PHP_INT_MAX, 4 );
add_filter( 'posts_results', array( $cap_manager, 'allowPreview' ), 10, 2 );
add_filter( 'wp_insert_post_data', array( $cap_manager, 'lockPendingStatus' ), 10, 2 );