Custom Post Type Capabilities

Question

I have a custom post type which I want authors to be able to edit others posts but no able to delete others posts. My code as follows:

$labels = array(
    'name'          => __( 'Book', 'textdomain' ),
    'singular_name' => __( 'Book', 'textdomain' ),
    'menu_name'     => __( 'Books', 'textdomain' ),
    'add_new'       => __( 'New book', 'textdomain' ),
    'add_new_item'  => __( 'New book', 'textdomain' ),
    'edit_item'     => __( 'Edit book', 'textdomain' ),
);
$args = array(
    'labels'        => $labels,
    'public'        => true,
    'menu_position' => 6,
    'menu_icon'     => 'dashicons-book',
    'has_archive'   => true,
    'supports'      => array( 'title', 'author' ),
    'capabilities'  => array(
        'edit_post'             => 'edit_posts',
        'read_post'             => 'edit_posts',
        'delete_post'           => 'edit_posts',
        'edit_posts'            => 'edit_posts',
        'edit_others_posts'     => 'edit_posts',
        'publish_posts'         => 'edit_posts',
        'read_private_posts'    => 'edit_others_posts',
        'delete_others_posts'   => 'edit_others_posts',
    ),
);
register_post_type( 'book', $args );

What I am experiencing with the above code is:

1. When 'edit_others_posts' => 'edit_posts', "mine" tab in admin post editor list doesn't show, and I want it to be always shown. Is it possible to force it back?
2. Even if 'delete_others_posts' => 'edit_others_posts' (author users don't have the capability to 'edit_others_posts'), authors can delete others posts.
3. If I modify the code above with 'edit_others_posts' => 'edit_others_posts', "mine" tab shows up but author users still can edit others posts, which confuse me.

I'm really not sure if I am using capabilities the right way or if what I intent to do is possible. Thanks in advance.

Answer 1

Ok - lets try this again :)

I added the map_meta_cap parameter which is needed to have delete_others_posts work. Now I was able to get authors to edit and view all posts but only delete their own.

$labels = array(
    'name'          => __( 'Book', 'textdomain' ),
    'singular_name' => __( 'Book', 'textdomain' ),
    'menu_name'     => __( 'Books', 'textdomain' ),
    'add_new'       => __( 'New book', 'textdomain' ),
    'add_new_item'  => __( 'New book', 'textdomain' ),
    'edit_item'     => __( 'Edit book', 'textdomain' ),
);
$args = array(
    'labels'        => $labels,
    'public'        => true,
    'menu_position' => 6,
    'menu_icon'     => 'dashicons-book',
    'has_archive'   => true,
    'supports'      => array( 'title', 'author' ),
    'map_meta_cap'  => true,
    'capabilities'  => array(
        'read_post' => 'read_post',
        'edit_post' => 'edit_posts',
        'edit_posts' => 'edit_posts',
        'edit_others_posts'     => 'edit_posts',
        'delete_others_posts'   => 'install_plugins',
    )

);
register_post_type( 'book', $args );