fix: Skip attachment if stream is empty

CHANGELOG.md

@@ -16,6 +16,7 @@
 
 - Fix logging loop with NLog sentry ([#1824](https://github.com/getsentry/sentry-dotnet/pull/1824))
 - Fix logging loop with Serilog sentry ([#1828](https://github.com/getsentry/sentry-dotnet/pull/1828))
+- Skip attachment if stream is empty ([#1854](https://github.com/getsentry/sentry-dotnet/pull/1854))
 
 ## 3.20.1
 

src/Sentry/Envelopes/Envelope.cs

@@ -180,7 +180,18 @@ internal void Serialize(Stream stream, IDiagnosticLogger? logger, ISystemClock c
                 {
                     try
                     {
-                        items.Add(EnvelopeItem.FromAttachment(attachment));
+                        // We pull the stream out here so we can length check
+                        // to avoid adding an invalid attachment
+                        var stream = attachment.Content.GetStream();
+                        if (stream.TryGetLength() != 0)
+                        {
+                            items.Add(EnvelopeItem.FromAttachment(attachment, stream));
+                        }
+                        else
+                        {
+                            logger?.LogWarning("Did not add '{0}' to envelope because the stream was empty.",
+                                attachment.FileName);
+                        }
                     }
                     catch (Exception exception)
                     {

src/Sentry/Envelopes/EnvelopeItem.cs

@@ -262,7 +262,11 @@ public static EnvelopeItem FromSession(SessionUpdate sessionUpdate)
         public static EnvelopeItem FromAttachment(Attachment attachment)
         {
             var stream = attachment.Content.GetStream();
+            return FromAttachment(attachment, stream);
+        }
 
+        internal static EnvelopeItem FromAttachment(Attachment attachment, Stream stream)
+        {
             var attachmentType = attachment.Type switch
             {
                 AttachmentType.Minidump => "event.minidump",

test/Sentry.Tests/Protocol/Envelopes/EnvelopeTests.cs

@@ -538,9 +538,11 @@ public async Task Roundtrip_WithEvent_WithAttachment_Success()
             Sdk = new SdkVersion { Name = "SDK-test", Version = "1.0.0" }
         };
 
+        using var attachmentStream = new MemoryStream(new byte[] {1, 2, 3});
+
         var attachment = new Attachment(
             AttachmentType.Default,
-            new StreamAttachmentContent(Stream.Null),
+            new StreamAttachmentContent(attachmentStream),
             "file.txt",
             null);
 
@@ -573,9 +575,11 @@ public async Task Roundtrip_WithEvent_WithSession_Success()
             Sdk = new SdkVersion { Name = "SDK-test", Version = "1.0.0" }
         };
 
+        using var attachmentStream = new MemoryStream(new byte[] {1, 2, 3});
+
         var attachment = new Attachment(
             AttachmentType.Default,
-            new StreamAttachmentContent(Stream.Null),
+            new StreamAttachmentContent(attachmentStream),
             "file.txt",
             null);
 
@@ -699,6 +703,23 @@ public void FromEvent_Header_IncludesSdkInformation()
         }).Should().BeTrue();
     }
 
+    [Fact]
+    public void FromEvent_EmptyAttachmentStream_DoesNotIncludeAttachment()
+    {
+        // Arrange
+        var attachment = new Attachment(
+            default,
+            new StreamAttachmentContent(Stream.Null),
+            "Screenshot.jpg",
+            "image/jpg");
+
+        // Act
+        var envelope = Envelope.FromEvent(new SentryEvent(), attachments: new List<Attachment> { attachment });
+
+        // Assert
+        envelope.Items.Should().HaveCount(1);
+    }
+
     [Fact]
     public async Task Serialization_RoundTrip_ReplacesSentAtHeader()
     {