Passing srcset to image attachment method

I can’t say I’ve tested this but here’s what you could to, it should in theory work.

The wp_get_attachment_image() functions 4th parameter is an array of attributes. You should be able to pass what you get returned from wp_get_attachment_image_srcset() to the attribute parameter as follows, sort of similar to the example seen on the docs.

$image_attrs="";
$image_id       = 123;
$image_size="full";
$image_srcset   = wp_get_attachment_image_srcset( $image_id, $image_size );

if( ! empty( $image_srcset ) ) {

    $image_attrs = array(
        'srcset' => esc_attr( $image_srcset ),
    );

}

$image_html = wp_get_attachment_image( $image_id, $image_size, false, $image_attrs );