Create custom unmarshaller for orders (#100)

* Create custom unmarshaller for orders

- We noticed an issue where some older orders were being sent
with line items that had their properties field set an empty
JSON object rather than the expected array. This was causing
an error when attempting to unmarshal.

* cleanup tests

Co-authored-by: Gord Currie <[email protected]>

fixtures/orderlineitems/properties_empty_object.json

@@ -0,0 +1,3 @@
+{
+    "properties": {}
+}

fixtures/orderlineitems/properties_invalid0.json

@@ -0,0 +1,3 @@
+{
+    "properties": {
+}

fixtures/orderlineitems/properties_invalid1.json

@@ -0,0 +1,5 @@
+{
+    "properties": {
+      "name": 2
+    }
+}

fixtures/orderlineitems/properties_invalid2.json

@@ -0,0 +1,7 @@
+{
+  "properties": [
+    {
+      "name": 2
+    }
+  ]
+}

fixtures/orderlineitems/properties_object.json

@@ -0,0 +1,6 @@
+{
+  "properties": {
+    "name": "property 1",
+    "value": 3
+  }
+}

fixtures/orderlineitems/valid.json

@@ -0,0 +1,88 @@
+{
+    "fulfillable_quantity": 1,
+    "fulfillment_service": "manual",
+    "fulfillment_status": "partial",
+    "gift_card": true,
+    "grams": 100,
+    "id": 254721536,
+    "name": "Soda",
+    "pre_tax_price": "9.00",
+    "price": "12.34",
+    "product_exists": true,
+    "product_id": 111475476,
+    "properties": [
+      {
+        "name": "note 1",
+        "value": "one"
+      },
+      {
+        "name": "note 2",
+        "value": 2
+      }
+    ],
+    "quantity": 1,
+    "requires_shipping": true,
+    "sku": "sku-123",
+    "tax_lines": [
+          {
+            "price": 13.50,
+            "rate": 0.06,
+            "title": "State tax"
+          },
+          {
+            "price": 12.50,
+            "rate": 0.05,
+            "title": "Federal tax"
+          }
+    ],
+    "taxable": true,
+    "title": "Soda Title",
+    "total_discount": "1.23",
+    "variant_id": 1234,
+    "variant_inventory_management": "shopify",
+    "variant_title": "Test Variant",
+    "vendor": "Test Vendor",
+    "origin_location": {
+      "id": 123,
+      "address1": "100 some street",
+      "address2": "",
+      "city": "Winnipeg",
+      "company": "Acme Corporation",
+      "country": "Canada",
+      "country_code": "CA",
+      "first_name": "Bob",
+      "last_name": "Smith",
+      "latitude": 49.811550,
+      "longitude": -97.189480,
+      "name": "test address",
+      "phone": "8675309",
+      "province": "Manitoba",
+      "province_code": "MB",
+      "zip": "R3Y 0L6"
+    },
+    "destination_location": {
+      "id": 124,
+      "address1": "200 some street",
+      "address2": "",
+      "city": "Winnipeg",
+      "company": "Acme Corporation",
+      "country": "Canada",
+      "country_code": "CA",
+      "first_name": "Bob",
+      "last_name": "Smith",
+      "latitude": 49.811550,
+      "longitude": -97.189480,
+      "name": "test address",
+      "phone": "8675309",
+      "province": "Manitoba",
+      "province_code": "MB",
+      "zip": "R3Y 0L6"
+    },
+    "applied_discount": {
+      "applied_discount": "test discount",
+      "description": "my test discount",
+      "value": "0.05",
+      "value_type": "percent",
+      "amount": "25.00"
+    }
+}

order.go

@@ -1,6 +1,7 @@
 package goshopify
 
 import (
+	"encoding/json"
 	"fmt"
 	"net/http"
 	"time"
@@ -184,6 +185,43 @@ type LineItem struct {
 	AppliedDiscount            *AppliedDiscount `json:"applied_discount,omitempty"`
 }
 
+// UnmarshalJSON custom unmarsaller for LineItem required to mitigate some older orders having LineItem.Properies
+// which are empty JSON objects rather than the expected array.
+func (li *LineItem) UnmarshalJSON(data []byte) error {
+	type alias LineItem
+	aux := &struct {
+		Properties json.RawMessage `json:"properties"`
+		*alias
+	}{alias: (*alias)(li)}
+
+	err := json.Unmarshal(data, &aux)
+	if err != nil {
+		return err
+	}
+	// if the first character is a '[' we unmarshal into an array
+	if len(aux.Properties) > 0 && aux.Properties[0] == '[' {
+		var p []NoteAttribute
+		err = json.Unmarshal(aux.Properties, &p)
+		if err != nil {
+			return err
+		}
+		li.Properties = p
+	} else { // else we unmarshal it into a struct
+		var p NoteAttribute
+		err = json.Unmarshal(aux.Properties, &p)
+		if err != nil {
+			return err
+		}
+		if p.Name == "" && p.Value == nil { // if the struct is empty we set properties to nil
+			li.Properties = nil
+		} else {
+			li.Properties = []NoteAttribute{p} // else we set them to an array with the property nested
+		}
+	}
+
+	return nil
+}
+
 type LineItemProperty struct {
 	Message string `json:"message"`
 }
@@ -310,6 +348,7 @@ func (s *OrderServiceOp) ListWithPagination(options interface{}) ([]Order, *Pagi
 
 	return resource.Orders, pagination, nil
 }
+
 // Count orders
 func (s *OrderServiceOp) Count(options interface{}) (int, error) {
 	path := fmt.Sprintf("%s/count.json", ordersBasePath)