Add validation to PO number for vendor invoices.

tailbone/views/vendors/invoices.py

@@ -105,18 +105,34 @@ class VendorInvoiceCrud(FileBatchCrud):
             handler = super(VendorInvoiceCrud, self).get_handler()
         return handler
 
+    def validate_po_number(self, value, field):
+        """
+        Let the invoice handler in effect determine if the user-provided
+        purchase order number is valid.
+        """
+        parser = require_invoice_parser(field.parent.parser_key.value)
+        vendor = get_vendor(Session(), parser.vendor_key)
+        try:
+            self.handler.validate_po_number(value, vendor)
+        except ValueError as error:
+            raise formalchemy.ValidationError(unicode(error))
+
     def configure_fieldset(self, fs):
         parsers = sorted(iter_invoice_parsers(), key=lambda p: p.display)
         parser_options = [(p.display, p.key) for p in parsers]
         parser_options.insert(0, ("(please choose)", ''))
         fs.parser_key.set(renderer=formalchemy.fields.SelectFieldRenderer,
                           options=parser_options)
+
+        fs.purchase_order_number.set(label=self.handler.po_number_title)
+        fs.purchase_order_number.set(validate=self.validate_po_number)
+
         fs.configure(
             include=[
                 fs.vendor.readonly(),
                 fs.filename.label("Invoice File"),
                 fs.parser_key.label("File Type"),
-                fs.purchase_order_number.label(self.handler.po_number_title),
+                fs.purchase_order_number,
                 fs.invoice_date.readonly(),
                 fs.created,
                 fs.created_by,