Allow SDK to handle No Content (204) responses

Previously, the SDK would throw an exception when trying to parse an empty string.
Now we will return the empty string, if a string response is requested.

If the caller was expecting a deserialized type, an exception will still be raised for no content.

ShipEngineSDK.Test/Helpers/MockShipEngineFixture.cs

@@ -79,7 +79,7 @@ public string StubRequest(HttpMethod method, string path, HttpStatusCode status,
         {
             var requestId = Guid.NewGuid().ToString();
             var responseMessage = new HttpResponseMessage(status);
-            responseMessage.Content = new StringContent(response);
+            responseMessage.Content = new StringContent(response ?? "");
             responseMessage.Headers.Add("x-shipengine-requestid", requestId);
             responseMessage.Headers.Add("request-id", requestId);
 

ShipEngineSDK.Test/ShipEngineClientTests.cs

@@ -167,7 +167,7 @@ public async Task SuccessResponseThatCannotBeParsedThrowsExceptionWithUnparsedRe
         }
 
         [Fact]
-        public async Task SuccessResponseWithNullContentThrowsShipEngineExceptionWithUnparsedResponse()
+        public async Task SuccessResponseWithNullStringContentThrowsShipEngineExceptionWithUnparsedResponse()
         {
             var config = new Config(apiKey: "test", timeout: TimeSpan.FromSeconds(0.5));
             var mockShipEngineFixture = new MockShipEngineFixture(config);
@@ -189,5 +189,39 @@ public async Task SuccessResponseWithNullContentThrowsShipEngineExceptionWithUnp
             Assert.Equal(responseBody, await ex.ResponseMessage.Content.ReadAsStringAsync());
             Assert.Equal(requestId, ex.RequestId);
         }
+
+        [Fact]
+        public async Task SuccessResponseWhenStringRequestedReturnsUnparsedString()
+        {
+            var config = new Config(apiKey: "test", timeout: TimeSpan.FromSeconds(0.5));
+            var mockShipEngineFixture = new MockShipEngineFixture(config);
+            var shipengine = mockShipEngineFixture.ShipEngine;
+
+            // this scenario is similar to unparseable JSON - except that it is valid JSON
+            var responseBody = @"The Response";
+            mockShipEngineFixture.StubRequest(HttpMethod.Delete, "/v1/something", System.Net.HttpStatusCode.OK,
+                responseBody);
+            var result = await shipengine.SendHttpRequestAsync<string>(HttpMethod.Delete, "/v1/something", "",
+                mockShipEngineFixture.HttpClient, config);
+
+            Assert.Equal(responseBody, result);
+        }
+
+        [Fact]
+        public async Task SuccessResponseWithNoContentCanBeReturnedIfStringRequested()
+        {
+            var config = new Config(apiKey: "test", timeout: TimeSpan.FromSeconds(0.5));
+            var mockShipEngineFixture = new MockShipEngineFixture(config);
+            var shipengine = mockShipEngineFixture.ShipEngine;
+
+            // this scenario is similar to unparseable JSON - except that it is valid JSON
+            string responseBody = null;
+            mockShipEngineFixture.StubRequest(HttpMethod.Delete, "/v1/something", System.Net.HttpStatusCode.OK,
+                responseBody);
+            var result = await shipengine.SendHttpRequestAsync<string>(HttpMethod.Delete, "/v1/something", "",
+                mockShipEngineFixture.HttpClient, config);
+
+            Assert.Null(responseBody);
+        }
     }
 }

ShipEngineSDK/ShipEngineClient.cs

@@ -129,6 +129,11 @@ private async Task<T> DeserializedResultOrThrow<T>(HttpResponseMessage response)
             }
 
             T? result;
+            // If the caller asked for a string, return the response as-is. This can be useful for no content responses.
+            if (typeof(T).IsAssignableFrom(typeof(string)))
+            {
+                return (T)(object)(contentString ?? "");
+            }
             try
             {
                 result = JsonSerializer.Deserialize<T>(contentString, JsonSerializerOptions);