[fix] Handle serializing array/list parameters in GET/DELETE query strings (#601)

Author: nwithan8

EasyPost.Tests/HttpTests/RequestTest.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using System.Net.Http;
 using EasyPost._base;
 using EasyPost.Http;
 using Xunit;
@@ -13,9 +14,29 @@ public class RequestTest
     [Fact]
     public void TestRequestDisposal()
     {
-        Request request = new("https://google.com", "not_a_real_endpoint", Method.Get, ApiVersion.V2, new Dictionary<string, object> { { "key", "value" } }, new Dictionary<string, string> { { "header_key", "header_value" } });
+        Request request = new("https://example.com", "not_a_real_endpoint", Method.Get, ApiVersion.V2, new Dictionary<string, object> { { "key", "value" } }, new Dictionary<string, string> { { "header_key", "header_value" } });
         CustomAssertions.DoesNotThrow(() => request.Dispose());
     }
 
+    [Fact]
+    public void TestQueryParameterList()
+    {
+        var parameters = new Dictionary<string, object>
+        {
+            { "key1", new List<string> { "value1", "value2" } },
+            { "key2", "value3" }
+        };
+
+        Request request = new("https://example.com", "not_a_real_endpoint", Method.Get, ApiVersion.V2, parameters, new Dictionary<string, string> { { "header_key", "header_value" } });
+
+        HttpRequestMessage httpRequestMessage = request.AsHttpRequestMessage();
+
+        string queryString = httpRequestMessage.RequestUri?.Query;
+
+        Assert.Contains("key1[]=value1", queryString); // Does not account for URL encoding
+        Assert.Contains("key1[]=value2", queryString); // Does not account for URL encoding
+        Assert.Contains("key2=value3", queryString); // Does not account for URL encoding
+    }
+
     #endregion
 }

EasyPost/Http/Request.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections;
 using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.Net.Http;
@@ -115,6 +116,9 @@ private void BuildQueryParameters()
             // add query parameters
             NameValueCollection query = HttpUtility.ParseQueryString(string.Empty);
 
+            // Separately store the list parameters to add them last
+            List<string> listParameters = new();
+
             // build query string from parameters
             foreach (KeyValuePair<string, object> param in _parameters)
             {
@@ -124,26 +128,52 @@ private void BuildQueryParameters()
                     continue;
                 }
 
-                query[param.Key] = param.Value switch
+                var @switch = new SwitchCase
                 {
-                    // TODO: Handle special conversions for other types
-                    // DateTime dateTime => dateTime.ToString("o", CultureInfo.InvariantCulture),
-                    var _ => param.Value.ToString(),
+                    { param.Value is IList, () => listParameters = AddListQueryParameter(listParameters, param.Key, (IList)param.Value) },
+                    { SwitchCaseScenario.Default, () => query[param.Key] = param.Value.ToString() },
                 };
+                @switch.MatchFirstTrue();
             }
 
-            // short circuit if no query parameters
-            if (query.Count == 0)
+            // Finalize the query string
+            string queryString = query.ToString() ?? string.Empty;
+
+            // Add list parameters to the query string
+            string parameterCharacter = queryString.Length == 0 ? "?" : "&";
+            foreach (string pair in listParameters)
             {
-                return;
+                queryString += $"{parameterCharacter}{pair}";
+                parameterCharacter = "&";
             }
 
             // rebuild the request URL with the query string appended
             var uriBuilder = new UriBuilder(_requestMessage.RequestUri!)
             {
-                Query = query.ToString(),
+                Query = queryString,
             };
-            _requestMessage.RequestUri = new Uri(uriBuilder.ToString());
+
+            // _requestMessage.RequestUri = new Uri(uriBuilder.ToString());
+            _requestMessage.RequestUri = uriBuilder.Uri;
+        }
+
+        private static List<string> AddListQueryParameter(List<string> pairs, string key, IList value)
+        {
+            string keyPrefix = $"{HttpUtility.UrlEncode(key)}[]";
+            // ReSharper disable once LoopCanBeConvertedToQuery
+            foreach (object? item in value)
+            {
+                string? itemString = item?.ToString();
+                if (itemString == null)
+                {
+                    continue;
+                }
+
+                string pair = $"{keyPrefix}={HttpUtility.UrlEncode(itemString)}";
+                pairs.Add(pair);
+            }
+
+            return pairs;
         }
 
         /// <inheritdoc cref="EasyPostClient._isDisposed"/>

EasyPost/Parameters/Tracker/All.cs

@@ -84,6 +84,7 @@ public class All : BaseAllParameters<Models.API.Tracker>
                 EndDatetime = dictionary.GetOrNull<string>("end_datetime"),
                 Carrier = dictionary.GetOrNull<string>("carrier"),
                 TrackingCode = dictionary.GetOrNull<string>("tracking_code"),
+                TrackingCodes = dictionary.GetOrNull<List<string>>("tracking_codes"),
             };
         }
     }