[Backport] WriteAsync may truncate data after Advance(int)

Author: BrennanConroy

pkg/Microsoft.Private.PackageBaseline/packageIndex.json

@@ -2601,7 +2601,8 @@
         "4.7.1",
         "4.7.2",
         "4.7.3",
-        "4.7.4"
+        "4.7.4",
+        "4.7.5"
       ],
       "BaselineVersion": "4.7.0",
       "InboxOn": {},
@@ -2612,7 +2613,8 @@
         "4.0.2.0": "4.7.0",
         "4.0.2.1": "4.7.1",
         "4.0.2.2": "4.7.3",
-        "4.0.2.3": "4.7.4"
+        "4.0.2.3": "4.7.4",
+        "4.0.2.4": "4.7.5"
       }
     },
     "System.IO.Pipes": {

src/System.IO.Pipelines/Directory.Build.props

@@ -1,8 +1,8 @@
 <Project>
   <Import Project="..\Directory.Build.props" />
   <PropertyGroup>
-    <AssemblyVersion>4.0.2.3</AssemblyVersion>
-    <PackageVersion>4.7.4</PackageVersion>
+    <AssemblyVersion>4.0.2.4</AssemblyVersion>
+    <PackageVersion>4.7.5</PackageVersion>
     <StrongNameKeyId>Open</StrongNameKeyId>
   </PropertyGroup>
 </Project>

src/System.IO.Pipelines/src/System/IO/Pipelines/Pipe.cs

@@ -1005,7 +1005,7 @@ private void WriteMultiSegment(ReadOnlySpan<byte> source)
                 }
 
                 // We filled the segment
-                _writingHead.End += writable;
+                _writingHead.End += _writingHeadBytesBuffered;
                 _writingHeadBytesBuffered = 0;
 
                 // This is optimized to use pooled memory. That's why we pass 0 instead of

src/System.IO.Pipelines/tests/PipeLengthTests.cs

@@ -278,5 +278,19 @@ public async Task NullExaminedAndConsumedNoops()
             ReadResult result = await _pipe.Reader.ReadAsync();
             _pipe.Reader.AdvanceTo(default, default);
         }
+
+        [Fact]
+        public async Task AdvanceFollowedByWriteAsyncTest()
+        {
+            Memory<byte> buffer = new byte[26];
+            Pipe pipe = new Pipe(new PipeOptions(minimumSegmentSize: 1));
+
+            var mem = pipe.Writer.GetMemory(14).Slice(0, 14);
+            buffer.Slice(0, 14).CopyTo(mem);
+            pipe.Writer.Advance(14);
+            await pipe.Writer.WriteAsync(buffer.Slice(14));
+            ReadResult res = await pipe.Reader.ReadAsync();
+            Assert.Equal(res.Buffer.Length, buffer.Length);
+        }
     }
 }

src/packages.builds

@@ -26,6 +26,9 @@
       <AdditionalProperties>$(AdditionalProperties)</AdditionalProperties>
     </Project>
     <!-- add specific builds / pkgproj's here to include in servicing builds -->
+    <Project Include="$(MSBuildThisFileDirectory)System.IO.Pipelines\pkg\System.IO.Pipelines.pkgproj">
+      <AdditionalProperties>$(AdditionalProperties)</AdditionalProperties>
+    </Project>
   </ItemGroup>
 
   <ItemGroup>