Merge pull request #1852 from OpenBazaar/zeroquantity

(#1844) Allow crypto currency listings with quantity of zero

Author: placer14

api/jsonapi_test.go

@@ -512,7 +512,7 @@ func TestCryptoListingsQuantity(t *testing.T) {
 		"POST", "/ob/listing", jsonFor(t, listing), 200, `{"slug": "crypto"}`,
 	})
 
-	listing.Item.Skus[0].BigQuantity = "0"
+	listing.Item.Skus[0].BigQuantity = "-1"
 	runAPITest(t, apiTest{
 		"POST", "/ob/listing", jsonFor(t, listing), 500, errorResponseJSON(repo.ErrCryptocurrencySkuQuantityInvalid),
 	})

repo/listing.go

@@ -2204,10 +2204,10 @@ func validateCryptocurrencyQuantity(listing *pb.Listing) error {
 				return fmt.Errorf("cannot validate nil sku")
 			}
 			if s.BigQuantity == "" {
-				return fmt.Errorf("sku bigQuantity empty")
+				return fmt.Errorf("sku quantity empty")
 			}
-			if ba, ok := new(big.Int).SetString(s.BigQuantity, 10); ok && ba.Cmp(big.NewInt(0)) <= 0 {
-				return fmt.Errorf("sku bigQuantity zero or less")
+			if ba, ok := new(big.Int).SetString(s.BigQuantity, 10); ok && ba.Cmp(big.NewInt(0)) < 0 {
+				return fmt.Errorf("sku quantity cannot be negative")
 			}
 			return nil
 		}