Shipping amount incorrect when hitting "Go back" on checkout

Question

I am using Drupal Commerce with Commerce Flat Rate and I have setup various different rates depending on the total order amount.

The normal use case works as expected, however if I am at the shipping checkout pane and I hit go back,hit continue, and then arrive again at the shipping pane again, the shipping amount is recalculated based on the previously calculated (order_total + shipping_cost), not on the original order_total if you know what I mean.

What hook and code should I use to remedy this so that the shipping cost is based on the original order_total the second time around like it was the first time around?

Is it possible to remove the shipping component of the order total on the first checkout page?

Should I try to detect when I am on the first checkout page whether I arrived from the shipping pane, and so try to remove the shipping price component from the order total?

Answer 1

Check out Per Product Shipping Buggy

Import this rule or a variant of it and adapt it to your use case:

{ "commerce_shipping_service_free_shipping" : {
"LABEL" : "Rate Free shipping",
"PLUGIN" : "rule",
"OWNER" : "rules",
"REQUIRES" : [ "commerce_shipping" ],
"USES VARIABLES" : { "commerce_order" : { "label" : "Order", "type" : "commerce_order" } },
"DO" : [
{ "commerce_shipping_delete_shipping_line_items" : { "commerce_order" : [ "commerce_order" ] } },
{ "commerce_shipping_service_rate_order" : {
"shipping_service_name" : "free_shipping",
"commerce_order" : [ "commerce-order" ]
}
}
]
}
}