Address PR feedback

src/libraries/System.Net.ServerSentEvents/src/PACKAGE.md

@@ -18,8 +18,8 @@ Asynchronously parsing event contents as strings
 
 ```csharp
 using HttpClient client = new();
-using Stream response = await client.GetStreamAsync("https://localhost:12345/sse");
-await foreach (SseItem<string> item in SseParser.Create(response).EnumerateAsync())
+using Stream stream = await client.GetStreamAsync("https://localhost:12345/sse");
+await foreach (SseItem<string> item in SseParser.Create(stream).EnumerateAsync())
 {
     Console.WriteLine(item.Data);
 }
@@ -29,9 +29,9 @@ Synchronously parsing event contents as JSON
 
 ```csharp
 MemoryStream stream = new(data);
-foreach (SseItem<Book> item in SseParser.Create(response, (eventType, bytes) => JsonSerializer.Deserialize<Book>(bytes)).Enumerate())
+foreach (SseItem<Book> item in SseParser.Create(stream, (eventType, bytes) => JsonSerializer.Deserialize<Book>(bytes)).Enumerate())
 {
-    Console.WriteLine(item.Author);
+    Console.WriteLine(item.Data.Author);
 }
 ```
 

src/libraries/System.Net.ServerSentEvents/src/Resources/Strings.resx

@@ -120,7 +120,4 @@
   <data name="InvalidOperation_EnumerateOnlyOnce" xml:space="preserve">
     <value>The enumerable may be enumerated only once.</value>
   </data>
-  <data name="InvalidOperation_InvalidStreamNegativeBytes" xml:space="preserve">
-    <value>The Stream implementation is invalid, returning a negative number from a read operation.</value>
-  </data>
-</root>
+</root>

src/libraries/System.Net.ServerSentEvents/src/System/Net/ServerSentEvents/SseParser_1.cs

@@ -352,6 +352,7 @@ private bool ProcessLine(out SseItem<T> sseItem, out int advance)
             if (fieldName.SequenceEqual("data"u8))
             {
                 // Spec: "Append the field value to the data buffer, then append a single U+000A LINE FEED (LF) character to the data buffer."
+                // Spec: "If the data buffer's last character is a U+000A LINE FEED (LF) character, then remove the last character from the data buffer."
 
                 // If there's nothing currently in the data buffer and we can easily detect that this line is immediately followed by
                 // an empty line, we can optimize it to just handle the data directly from the line buffer, rather than first copying
@@ -462,16 +463,16 @@ private int FillLineBuffer()
                 _lineBuffer, offset, _lineBuffer.Length - offset);
 #endif
 
-            if (bytesRead <= 0)
+            if (bytesRead > 0)
+            {
+                _lineLength += bytesRead;
+            }
+            else
             {
                 _eof = true;
-                if (bytesRead < 0)
-                {
-                    throw new InvalidOperationException(SR.InvalidOperation_InvalidStreamNegativeBytes);
-                }
+                bytesRead = 0;
             }
 
-            _lineLength += bytesRead;
             return bytesRead;
         }
 
@@ -489,16 +490,16 @@ private async ValueTask<int> FillLineBufferAsync(CancellationToken cancellationT
 #endif
                 .ConfigureAwait(false);
 
-            if (bytesRead <= 0)
+            if (bytesRead > 0)
+            {
+                _lineLength += bytesRead;
+            }
+            else
             {
                 _eof = true;
-                if (bytesRead < 0)
-                {
-                    throw new InvalidOperationException(SR.InvalidOperation_InvalidStreamNegativeBytes);
-                }
+                bytesRead = 0;
             }
 
-            _lineLength += bytesRead;
             return bytesRead;
         }
 

src/libraries/System.Net.ServerSentEvents/tests/SseParserTests.cs

@@ -726,27 +726,6 @@ public void NonGenericEnumerator_ProducesExpectedItems()
             Assert.False(e.MoveNext());
         }
 
-        [Theory]
-        [InlineData(false)]
-        [InlineData(true)]
-        public async Task InvalidStream_ReturnsNegativeValueFromRead_Throws(bool useAsync)
-        {
-            using Stream stream = new InvalidReadStream();
-
-            SseParser<string> parser = SseParser.Create(stream);
-
-            if (useAsync)
-            {
-                await using IAsyncEnumerator<SseItem<string>> e = parser.EnumerateAsync().GetAsyncEnumerator();
-                await Assert.ThrowsAsync<InvalidOperationException>(async () => await e.MoveNextAsync());
-            }
-            else
-            {
-                using IEnumerator<SseItem<string>> e = parser.Enumerate().GetEnumerator();
-                Assert.Throws<InvalidOperationException>(() => e.MoveNext());
-            }
-        }
-
         [Theory]
         [MemberData(nameof(NewlineTrickleAsyncData))]
         public async Task MultipleItemParsers_OpenAI_StreamingResponse(string newline, bool trickle, bool useAsync)
@@ -978,23 +957,6 @@ public override async ValueTask<int> ReadAsync(Memory<byte> buffer, Cancellation
                 await Task.Yield();
                 return await base.ReadAsync(buffer.Slice(0, Math.Min(buffer.Length, 1)), cancellationToken);
             }
-#endif
-        }
-
-        private sealed class InvalidReadStream : MemoryStream
-        {
-            public override int Read(byte[] buffer, int offset, int count) =>
-                -1;
-
-            public override Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken) =>
-                Task.FromResult(-1);
-
-#if NET
-            public override int Read(Span<byte> buffer) =>
-                -1;
-
-            public override ValueTask<int> ReadAsync(Memory<byte> buffer, CancellationToken cancellationToken = default) =>
-                ValueTask.FromResult(-1);
 #endif
         }
     }