Optional Parameters Are Not Optional

[calvinanderson]

Calling CreateOrder() with CreateOrderParams{}:

// CreateOrderParams should be passed to `CreateOrder` to create an order․
type CreateOrderParams struct {
    ...
    Amount          float64         `json:"amount"`
    Shipping        float64         `json:"shipping"`
    SalesTax        float64         `json:"sales_tax"`
    ...
}

Amount is an optional field in the API, however this will always be the zero value of the struct member when posting to the endpoint (so, 0)

This could possibly be solved by making this a pointer to float64 and checking for nil, as I am now required to work out this before calling CreateOrder() or I will get an error.

[ScottRudiger]

@calvinanderson Thanks for the issue!

Amount is actually a required field per the API reference:

If it helps work out the logic, there are (at least) two different cases with the client as-is:

1. Amount & LineItems add up correctly

   201 Order created

   taxjar.CreateOrderParams{
   // ...
   Amount:          36.21,
   Shipping: 5,
   SalesTax: 0,
   LineItems: []taxjar.OrderLineItem{
   {
   ID:                "1",
   Quantity:          1,
   ProductIdentifier: "12-34243-9",
   Description:       "Fuzzy Sweater",
   ProductTaxCode:    "20010",
   UnitPrice:         36.72,
   Discount:          5.51,
   SalesTax:          0,
   },
   },
   }

2. Amount is empty or zero and LineItems includes items

   400 Bad Request - Order amount must be equal to the sum of line items and shipping

   taxjar.CreateOrderParams{
   // ...
   // Amount:          36.21,
   Shipping: 5,
   SalesTax: 0,
   LineItems: []taxjar.OrderLineItem{
   {
   ID:                "1",
   Quantity:          1,
   ProductIdentifier: "12-34243-9",
   Description:       "Fuzzy Sweater",
   ProductTaxCode:    "20010",
   UnitPrice:         36.72,
   Discount:          5.51,
   SalesTax:          0,
   },
   },
   }

If we pass nil for an empty Amount instead of 0, a different error would be returned since Amount is required:

406 Not Acceptable - amount is missing, amount is empty

type CreateOrderParams struct {
// ...
Amount          float64         `json:"amount,omitempty"`
Shipping        float64         `json:"shipping"`
SalesTax        float64         `json:"sales_tax"`
...
}

Since Amount is required, our inclination is to pass 0 when omitted.

[calvinanderson]

Thanks, sorry, I had thought that is was an optional param like in the calculate sales tax endpoint.

[ScottRudiger]

No worries! We know this is confusing since Amount excludes shipping when calculating tax, but includes shipping when creating an order as well. We hope to offer more consistency in a future version of the API.