Generate variant unit options in Ruby

This re-implements Angular JS function VariantUnitManager.variantUnitOptions()

Well.. almost. See next commit.

app/services/weights_and_measures.rb

@@ -20,6 +20,37 @@ class WeightsAndMeasures
     scales[product_scale.to_f]['system']
   end
 
+  # @returns enumerable with label and value for select
+  def self.variant_unit_options
+    available_units_sorted.flat_map do |measurement, measurement_info|
+      measurement_info.filter_map do |scale, unit_info|
+        scale_clean =
+          ActiveSupport::NumberHelper.number_to_rounded(scale, precision: nil,
+                                                               strip_insignificant_zeros: true)
+        [
+          "#{I18n.t(measurement)} (#{unit_info['name']})", # Label (eg "Weight (g)")
+          "#{measurement}_#{scale_clean}", # Scale ID (eg "weight_1")
+        ]
+      end
+    end <<
+      [
+        I18n.t('items'),
+        'items'
+      ]
+  end
+
+  def self.available_units
+    Spree::Config.available_units.split(",")
+  end
+
+  def self.available_units_sorted
+    self::UNITS.transform_values do |measurement_info|
+      measurement_info.filter do |_scale, unit_info|
+        available_units.include?(unit_info['name'])
+      end.sort.to_h # sort by unit (hash key)
+    end
+  end
+
   private
 
   UNITS = {
@@ -49,7 +80,7 @@ class WeightsAndMeasures
     return @units[@variant.product.variant_unit] if ignore_available_units
 
     @units[@variant.product.variant_unit]&.reject { |_scale, unit_info|
-      available_units.exclude?(unit_info['name'])
+      self.class.available_units.exclude?(unit_info['name'])
     }
   end
 
@@ -67,8 +98,4 @@ class WeightsAndMeasures
 
     largest_unit
   end
-
-  def available_units
-    Spree::Config.available_units.split(",")
-  end
 end

spec/services/weights_and_measures_spec.rb

@@ -55,7 +55,56 @@ describe WeightsAndMeasures do
     end
   end
 
-  describe "#scale_for_unit_value" do
+  describe "#variant_unit_options" do
+    let(:available_units) { "mg,g,kg,T,mL,cL,dL,L,kL,lb,oz,gal" }
+    subject { WeightsAndMeasures.variant_unit_options }
+
+    before do
+      allow(Spree::Config).to receive(:available_units).and_return(available_units)
+    end
+
+    it "returns options for each unit" do
+      expected_array = [
+        ["Weight (mg)", "weight_0.001"],
+        ["Weight (g)", "weight_1"],
+        ["Weight (oz)", "weight_28.35"],
+        ["Weight (lb)", "weight_453.6"],
+        ["Weight (kg)", "weight_1000"],
+        ["Weight (T)", "weight_1000000"],
+        ["Volume (mL)", "volume_0.001"],
+        ["Volume (cL)", "volume_0.01"],
+        ["Volume (dL)", "volume_0.1"],
+        ["Volume (L)", "volume_1"],
+        ["Volume (gal)", "volume_4.54609"],
+        ["Volume (kL)", "volume_1000"],
+        ["Items", "items"],
+      ]
+      pending "imperial measurements are duplicated"
+      expect(subject).to match_array expected_array # diff each element
+      expect(subject).to eq expected_array # test ordering also
+    end
+
+    describe "filtering available units" do
+      let(:available_units) { "g,kg,mL,L,lb,oz" }
+
+      it "returns options for available units only" do
+        expected_array = [
+          ["Weight (g)", "weight_1"],
+          ["Weight (oz)", "weight_28.35"],
+          ["Weight (lb)", "weight_453.6"],
+          ["Weight (kg)", "weight_1000"],
+          ["Volume (mL)", "volume_0.001"],
+          ["Volume (L)", "volume_1"],
+          ["Items", "items"],
+        ]
+        pending "imperial measurements are duplicated"
+        expect(subject).to match_array expected_array # diff each element
+        expect(subject).to eq expected_array # test ordering also
+      end
+    end
+  end
+
+  describe "#scales_for_unit_value" do
     context "weight" do
       before do
         allow(product).to receive(:variant_unit) { "weight" }