Now it's possible to edit the Menu order with negative values

Author: pmusolino

WooCommerce/Classes/Tools/UnitInputFormatter/IntegerInputFormatter.swift

@@ -3,6 +3,11 @@ import Foundation
 /// `UnitInputFormatter` implementation for integer number input (positive, negative, or zero)
 ///
 struct IntegerInputFormatter: UnitInputFormatter {
+    
+    /// The default value used by format() when the text is empty or the number formatter return a nil value
+    ///
+    let defaultValue: String
+    
     private let numberFormatter: NumberFormatter = {
         let numberFormatter = NumberFormatter()
         numberFormatter.allowsFloats = false
@@ -11,18 +16,28 @@ struct IntegerInputFormatter: UnitInputFormatter {
 
     func isValid(input: String) -> Bool {
         guard input.isEmpty == false else {
-            // Allows empty input to be replaced by 0.
+            // Allows empty input to be replaced by defaultValue
             return true
         }
-        return numberFormatter.number(from: input) != nil
+        return numberFormatter.number(from: input) != nil || input == "-"
     }
 
     func format(input text: String?) -> String {
         guard let text = text, text.isEmpty == false else {
-            return "0"
+            return defaultValue
+        }
+        
+        var formattedText = numberFormatter.number(from: text)?.stringValue ?? defaultValue
+        
+        // The minus sign is mantained if present
+        let minus: Character = "-"
+        if text.first == minus {
+            formattedText = String(minus) + formattedText.replacingOccurrences(of: "-", with: "")
         }
-
-        let formattedText = numberFormatter.number(from: text)?.stringValue ?? "0"
         return formattedText
     }
+    
+    init(defaultValue: String = "0") {
+        self.defaultValue = defaultValue
+    }
 }

WooCommerce/Classes/ViewRelated/Products/Edit Product/Product Settings/Menu Order/ProductMenuOrderViewController.swift

@@ -146,7 +146,7 @@ private extension ProductMenuOrderViewController {
             }
             }, onTextDidBeginEditing: {
                 //TODO: Add analytics track
-        }, inputFormatter: IntegerInputFormatter())
+        }, inputFormatter: IntegerInputFormatter(defaultValue: ""))
         cell.configure(viewModel: viewModel)
         cell.textField.applyBodyStyle()
         cell.textField.keyboardType = .numbersAndPunctuation

WooCommerce/WooCommerceTests/Tools/IntegerInputFormatterTests.swift

@@ -3,7 +3,7 @@ import XCTest
 @testable import WooCommerce
 
 final class IntegerInputFormatterTests: XCTestCase {
-    private let formatter = IntegerInputFormatter()
+    private let formatter = IntegerInputFormatter(defaultValue: "0")
 
     // MARK: test cases for `isValid(input:)`