Accept “invalid” quantity, price, and discount on invoice update

This is for “free products”, where the user adds an invoice row, does
not select a product from the search, and clicks the update button.
Numerus should select “appropriate” values for those that are left
unspecified.

I also no longer require the product_id to be an integer; if it is
empty, then it is assumed to be a “free product”.

pkg/invoices.go

@@ -661,6 +661,7 @@ func (form *invoiceForm) Update() {
 	form.Products = nil
 	for n, product := range products {
 		if product.Quantity.Val != "0" {
+			product.Update()
 			if n != len(form.Products) {
 				product.Index = len(form.Products)
 				product.Rename()
@@ -835,7 +836,9 @@ func (form *invoiceProductForm) Parse(r *http.Request) error {
 
 func (form *invoiceProductForm) Validate() bool {
 	validator := newFormValidator()
-	validator.CheckRequiredInput(form.ProductId, gettext("Product ID can not be empty.", form.locale))
+	if form.InvoiceProductId.Val != "" {
+		validator.CheckValidInteger(form.ProductId, 1, math.MaxInt32, gettext("Product ID must be a number greater than zero.", form.locale))
+	}
 	validator.CheckRequiredInput(form.Name, gettext("Name can not be empty.", form.locale))
 	if validator.CheckRequiredInput(form.Price, gettext("Price can not be empty.", form.locale)) {
 		validator.CheckValidDecimal(form.Price, form.company.MinCents(), math.MaxFloat64, gettext("Price must be a number greater than zero.", form.locale))
@@ -851,6 +854,22 @@ func (form *invoiceProductForm) Validate() bool {
 	return validator.AllOK()
 }
 
+func (form *invoiceProductForm) Update() {
+	validator := newFormValidator()
+	if !validator.CheckValidDecimal(form.Price, form.company.MinCents(), math.MaxFloat64, "") {
+		form.Price.Val = "0.0"
+		form.Price.Errors = nil
+	}
+	if !validator.CheckValidInteger(form.Quantity, 0, math.MaxInt32, "") {
+		form.Quantity.Val = "1"
+		form.Quantity.Errors = nil
+	}
+	if !validator.CheckValidInteger(form.Discount, 0, 100, "") {
+		form.Discount.Val = "0"
+		form.Discount.Errors = nil
+	}
+}
+
 func (form *invoiceProductForm) MustFillFromDatabase(ctx context.Context, conn *Conn, slug string) bool {
 	return !notFoundErrorOrPanic(conn.QueryRow(ctx, `
 		select product_id

pkg/pgtypes.go

@@ -17,8 +17,12 @@ func (src NewInvoiceProductArray) EncodeBinary(ci *pgtype.ConnInfo, buf []byte)
 	}
 	var values [][]interface{}
 	for _, form := range src {
+		var productId interface{} = form.ProductId.Val
+		if form.ProductId.Val == "" {
+			productId = nil
+		}
 		values = append(values, []interface{}{
-			form.ProductId.Val,
+			productId,
 			form.Name.Val,
 			form.Description.Val,
 			form.Price.Val,