fix: avoid null exception when received body is empty but recorded body isn't (#59)

Author: jhonny-apiiro

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 - Add .NET 8.0 support
 - `AdvancedSettings` uses `MatchRules.Default` instead of a new instance of `MatchRules` if not provided during construction
+- Fix `NullReferenceException` when trying to match by body with a null body (`refit` compatibility)
 
 ## v0.9.0 (2023-05-17)
 

EasyVCR.Tests/ClientTest.cs

@@ -513,6 +513,26 @@ public async Task TestMatchNonJsonBody()
             Assert.IsNotNull(response);
         }
 
+        [TestMethod]
+        public async Task TestMatchEmptyStringBodyToNonEmptyStringBody()
+        {
+            var cassette = TestUtils.GetCassette("test_match_empty_body");
+            cassette.Erase(); // Erase cassette before recording
+
+            const string url = "https://httpbin.org/post";
+
+            var client = HttpClients.NewHttpClient(cassette, Mode.Record);
+            var someContent = new ByteArrayContent(Encoding.UTF8.GetBytes("non_empty_string_body"));
+            _ = await client.PostAsync(url, someContent);
+
+            // try to replay the request with match by body enforcement
+            client = HttpClients.NewHttpClient(cassette, Mode.Replay, new AdvancedSettings
+            {
+                MatchRules = new MatchRules().ByBody()
+            });
+            var emptyContent = new ByteArrayContent(Encoding.UTF8.GetBytes(string.Empty));
+            await Assert.ThrowsExceptionAsync<VCRException>(async () => await client.PostAsync(url, emptyContent), $"No interaction found for request POST {url}");
+        }
 
         [TestMethod]
         public async Task TestInteractionElements()

EasyVCR/InternalUtilities/Extensions.cs

@@ -0,0 +1,7 @@
+namespace EasyVCR.InternalUtilities
+{
+    public static class Extensions
+    {
+        public static bool IsEmptyStringOrNull(this string? str) => str == null || string.IsNullOrWhiteSpace(str);
+    }
+}

EasyVCR/MatchRules.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Web;
+using EasyVCR.InternalUtilities;
 using EasyVCR.RequestElements;
 using JsonSerialization = EasyVCR.InternalUtilities.JSON.Serialization;
 using XmlSerialization = EasyVCR.InternalUtilities.XML.Serialization;
@@ -132,7 +133,7 @@ public MatchRules ByBody(List<CensorElement>? ignoredElements = null)
                     return true;
 
                 if (received.Body == null || recorded.Body == null)
-                    // one has a null body, so they don't match
+                    // one has a null body, the other does not, so they don't match
                     return false;
 
                 var receivedBody = received.Body;
@@ -155,11 +156,24 @@ public MatchRules ByBody(List<CensorElement>? ignoredElements = null)
                     // not JSON, using the string as it is
                 }
 
+                if (receivedBody.IsEmptyStringOrNull())
+                    // short-cut if the received body is empty
+                    receivedBody = null;
+
+                if (recordedBody.IsEmptyStringOrNull())
+                    // short-cut if the recorded body is empty
+                    recordedBody = null;
+
                 if (receivedBody == null && recordedBody == null)
                     // both have empty string bodies, so they match
                     return true;
 
-                return receivedBody!.Equals(recordedBody, StringComparison.OrdinalIgnoreCase);
+                if (receivedBody == null || recordedBody == null)
+                    // one has a null body, the other does not, so they don't match
+                    return false;
+
+                // if the bodies are not null, then we can compare them
+                return receivedBody.Equals(recordedBody, StringComparison.OrdinalIgnoreCase);
             });
             return this;
         }