XpsDocumentWriter.Write fails with NotSupportedException

[thomasclaudiushuber]

• .NET Core Version: 3.0.100-preview8-013410
• Windows version: 1903
• Does the bug reproduce also in WPF for .NET Framework 4.8?: No

Problem description:
XpsDocumentWriter.Write fails with NotSupportedException with the message "This stream from ZipArchiveEntry does not support seeking."

Actual behavior:
Message:
System.NotSupportedException : This stream from ZipArchiveEntry does not support seeking.
Stack Trace:
at WrappedStream.ThrowIfCantSeek()
at WrappedStream.SetLength(Int64 value)
at ZipWrappingStream.SetLength(Int64 value)
at ZipPackagePart.GetStreamCore(FileMode streamFileMode, FileAccess streamFileAccess)
at PackagePart.GetStream(FileMode mode, FileAccess access)
at PackagePart.GetStream(FileMode mode)
at XmlPartEditor.OpenDocumentForWrite()
at XpsPackagingPolicy.AcquireXmlWriterForFixedDocumentSequence()
at XpsSerializationManager.AcquireXmlWriter(Type writerType)
at DocumentSequenceSerializer.get_XmlWriter()
at DocumentSequenceSerializer.PersistObjectData(SerializableObjectContext serializableObjectContext)
at ReachSerializer.SerializeObject(Object serializedObject)
at XpsSerializationManager.SaveAsXaml(Object serializedObject)
at XpsDocumentWriter.SaveAsXaml(Object serializedObject, Boolean isSync)
at XpsDocumentWriter.Write(FixedDocumentSequence fixedDocumentSequence)

Expected behavior:
It should just create the XPS like in .NET Framework.

Minimal repro:
I've created a test project with a single test that shows the problem. The test succeeds on .NET Framework, but fails on .NET Core: https://github.com/thomasclaudiushuber/XpsNetCoreTests

[weltkante]

Related to #585 and PR #1311 - you may want to retry with nightly builds of preview8 - but I don't think your case is actually fixed yet, since the PR was mostly about reading streams, not writing them.

[edit] actually I think the PR #1311 is broken, because it wraps writing into a memory stream. While it may no longer throw it probably doesn't flush the writes to the original stream either.

[thomasclaudiushuber]

@weltkante Thanks for linking. I've downloaded already the latest nightly build, but it's not fixed yet.

Yes, PR #1311 looks like it is fixing it. Let's see.

[weltkante]

@thomasclaudiushuber does this still throw in nightly preview8 or just drops data silently? If it still throws I may want to open a separate issue for revisiting PR #1311 because I think it doesn't handle wrapping writable streams correctly.

[thomasclaudiushuber]

@weltkante I just tried it again. It throws exactly the same exception on preview8-013410. I've updated the preview version in the issue to that version.

[rladuca]

I'll look at this in the context of the broader discussion about the seekability change.

From the testing we did on the backend, it looked like everything was fine with the passthrough, but perhaps we missed a scenario.

[rladuca]

I just dipped into this and it looks like there are some parts of the code in ReachFramework that were missed when wrapping the GetStream functions in #1311 .

In light of @weltkante's comments I want to make 100% certain that these parts can use the same extensions without breaking.

[rladuca]

Nothing in this repro goes through the extension functions as far as I can tell. This actually may be a bug within packaging.

>	System.IO.Compression.dll!System.IO.Compression.WrappedStream.ThrowIfCantSeek() Line 88	C#
 	System.IO.Compression.dll!System.IO.Compression.WrappedStream.SetLength(long value) Line 111	C#
 	System.IO.Packaging.dll!System.IO.Packaging.ZipWrappingStream.SetLength(long value) Line 76	C#
 	System.IO.Packaging.dll!System.IO.Packaging.ZipPackagePart.GetStreamCore(System.IO.FileMode streamFileMode, System.IO.FileAccess streamFileAccess) Line 34	C#
 	System.IO.Packaging.dll!System.IO.Packaging.PackagePart.GetStream(System.IO.FileMode mode, System.IO.FileAccess access) Line 323	C#
 	System.IO.Packaging.dll!System.IO.Packaging.PackagePart.GetStream(System.IO.FileMode mode) Line 292	C#
 	ReachFramework.dll!System.Windows.Xps.Packaging.XmlPartEditor.OpenDocumentForWrite() Line 259	C#

WPF is asking for a PackagePart to be opened FileMode.Create. ZipPackagePart eventually attempts to do the following specifically for FileMode.Create:
https://github.com/dotnet/corefx/blob/a10890f4ffe0fadf090c922578ba0e606ebdd16c/src/System.IO.Packaging/src/System/IO/Packaging/ZipPackagePart.cs#L30-L36

The call tempStream.SetLength(0) is what is causing this exception. The underlying stream isn't seekable, which ZipPackagePart is expecting. I don't yet know why this is the case, I have to take a deeper look to see if something WPF is doing prior to calling GetStream is the issue or if this is an actual bug with System.IO.Packaging or System.IO.Compression.

[rladuca]

ZipArchiveEntry.GetDataCompressor created a new DeflateStream which is then wrapped, along with the original stream, by CheckSumAndSizeWriteStream.
https://github.com/dotnet/corefx/blob/78589e4d2c98bf71cefa4dbc94cde3783b60a934/src/System.IO.Compression/src/System/IO/Compression/ZipArchiveEntry.cs#L600

CheckSumAndSizeWriteStream is never seekable and doesn't support SetPosition:
https://github.com/dotnet/corefx/blob/a10890f4ffe0fadf090c922578ba0e606ebdd16c/src/System.IO.Compression/src/System/IO/Compression/ZipCustomStreams.cs#L364

I don't see how WPF is influencing these calls, I'm going to write a repro without using WPF and see if I can cause the same problem to occur with a reasonable console app. If I can do that I will file a bug on CoreFX and convert this to tracking.

[weltkante]

I'm wondering how the streams you were seeing in the existing extension method calls were ever seekable, weren't they coming from the same zip implementation? For what its worth writable streams not beeing seekable could be by design as well, because it allows streaming them through the compressor in a write-through way. If they were seekable they'd had to buffer everything and compress on Dispose.

[rladuca]

Opening an existing document as ReadWrite gave me a seekable stream.

That's an entirely different path than Create. The ReadWrite path would open a deflate stream and read the entire stream into memory, basically what we were doing to wrap it.

https://github.com/dotnet/corefx/blob/78589e4d2c98bf71cefa4dbc94cde3783b60a934/src/System.IO.Compression/src/System/IO/Compression/ZipArchiveEntry.cs#L697

[rladuca]

Sorry meant to link the place where it loads as well:
https://github.com/dotnet/corefx/blob/78589e4d2c98bf71cefa4dbc94cde3783b60a934/src/System.IO.Compression/src/System/IO/Compression/ZipArchiveEntry.cs#L340