Merge pull request #9497 from jibees/9493-fix-issues-around-rounding-in-imperial-metric-system

Avoid floating rounded errors when using imperial or metric system

app/assets/javascripts/admin/all.js

@@ -105,6 +105,8 @@
 //= require moment/locale/tr.js
 //= require moment/locale/pl.js
 
+//= require js-big-decimal/dist/web/js-big-decimal.min.js
+
 // foundation
 //= require ../shared/mm-foundation-tpls-0.9.0-20180826174721.min.js
 

app/assets/javascripts/admin/products/controllers/units_controller.js.coffee

@@ -32,7 +32,7 @@ angular.module("admin.products")
         if match
           $scope.product.master.unit_value  = PriceParser.parse(match[1])
           $scope.product.master.unit_value  = null if isNaN($scope.product.master.unit_value)
-          $scope.product.master.unit_value *= $scope.product.variant_unit_scale if $scope.product.master.unit_value && $scope.product.variant_unit_scale
+          $scope.product.master.unit_value = window.bigDecimal.multiply($scope.product.master.unit_value, $scope.product.variant_unit_scale, 2) if $scope.product.master.unit_value && $scope.product.variant_unit_scale
           $scope.product.master.unit_description = match[3]
       else
         value = $scope.product.master.unit_value

app/assets/javascripts/admin/products/controllers/variant_units_controller.js.coffee

@@ -23,10 +23,10 @@ angular.module("admin.products").controller "variantUnitsCtrl", ($scope, Variant
 
   $scope.updateValue = ->
     unit_value_human = angular.element('#unit_value_human').val()
-    $scope.unit_value = PriceParser.parse(unit_value_human) * $scope.scale
+    $scope.unit_value = bigDecimal.multiply(PriceParser.parse(unit_value_human), $scope.scale, 2)
 
   variant_unit_value = angular.element('#variant_unit_value').val()
-  $scope.unit_value_human = variant_unit_value / $scope.scale
+  $scope.unit_value_human = parseFloat(bigDecimal.divide(variant_unit_value, $scope.scale, 2))
 
   $timeout -> $scope.processUnitPrice()
   $timeout -> $scope.updateValue()

app/services/variant_units/option_value_namer.rb

@@ -56,7 +56,7 @@ module VariantUnits
     def option_value_value_unit_scaled
       unit_scale, unit_name = scale_for_unit_value
 
-      value = @variant.unit_value / unit_scale
+      value = BigDecimal(@variant.unit_value / unit_scale, 6)
 
       [value, unit_name]
     end

package.json

@@ -44,6 +44,7 @@
     "flatpickr": "^4.6.9",
     "foundation-sites": "^5.5.2",
     "jquery-ui": "1.13.0",
+    "js-big-decimal": "^1.3.5",
     "moment": "^2.29.1",
     "mrujs": "^0.7.4",
     "select2": "^4.0.13",

spec/javascripts/unit/admin/products/units_controller_spec.js.coffee

@@ -17,7 +17,8 @@ describe "unitsCtrl", ->
     inject ($rootScope, $controller, VariantUnitManager) ->
       scope = $rootScope
       ctrl = $controller 'unitsCtrl', {$scope: scope, VariantUnitManager: VariantUnitManager}
-
+    window.bigDecimal = jasmine.createSpyObj "bigDecimal", ["multiply"]
+    window.bigDecimal.multiply.and.callFake (a, b, c) -> a * b
 
   describe "interpretting variant_unit_with_scale", ->
     it "splits string with one underscore and stores the two parts", ->
@@ -93,3 +94,11 @@ describe "unitsCtrl", ->
         scope.processUnitValueWithDescription()
         expect(scope.product.master.unit_value).toEqual 22.22
         expect(scope.product.master.unit_description).toEqual "things"
+
+      it "handles nice rounded division", ->
+        # this is a bit absurd, but it assure use that bigDecimal is called
+        window.bigDecimal.multiply.and.returnValue 0.7
+        scope.product.master.unit_value_with_description = "700"
+        scope.product.variant_unit_scale = 0.001
+        scope.processUnitValueWithDescription()
+        expect(scope.product.master.unit_value).toEqual 0.7