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Incomplete file when using StreamWriter / WriteLineAsync with .NET 6 preview 3 #52811

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meziantou opened this issue May 15, 2021 · 3 comments · Fixed by #52812
Closed

Incomplete file when using StreamWriter / WriteLineAsync with .NET 6 preview 3 #52811

meziantou opened this issue May 15, 2021 · 3 comments · Fixed by #52812
Labels
area-System.IO untriaged New issue has not been triaged by the area owner

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@meziantou
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Description

When using a StreamWriter to write a file line by line, the beginning of the file is missing.

using System.IO;
using System.Linq;
using System.Text;

await using var writer = new StreamWriter("file.txt", append: false, Encoding.UTF8);
foreach (var url in Enumerable.Range(0, 1000).Select(i => "Line " + i))
{
    await writer.WriteLineAsync(url);
}

You can see that the file start at the middle of line 113:

image

Configuration

C:\Users\mezia>dotnet --info
.NET SDK (reflecting any global.json):
 Version:   6.0.100-preview.3.21202.5
 Commit:    aee38a6dd4

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.19042
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\6.0.100-preview.3.21202.5\

Host (useful for support):
  Version: 6.0.0-preview.3.21201.4
  Commit:  236cb21e3c

.NET SDKs installed:
  3.1.409 [C:\Program Files\dotnet\sdk]
  5.0.104 [C:\Program Files\dotnet\sdk]
  5.0.203 [C:\Program Files\dotnet\sdk]
  5.0.300-preview.21228.15 [C:\Program Files\dotnet\sdk]
  6.0.100-preview.3.21202.5 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.All 2.1.27 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.28 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.App 2.1.27 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.28 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.1.14 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.1.15 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 5.0.4 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 5.0.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 5.0.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 6.0.0-preview.3.21201.13 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 2.1.27 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.11 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.14 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.15 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 5.0.4 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 5.0.5 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 5.0.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 6.0.0-preview.3.21201.4 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 3.1.11 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 3.1.14 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 3.1.15 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 5.0.4 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 5.0.5 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 5.0.6 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 6.0.0-preview.3.21201.3 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Regression?

Yes, it works with .NET 5.0

Other information

It works well with WriteLine instead of WriteLineAsync. File.WriteAllLineAsync is also ok.
@dotnet-issue-labeler
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I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

@dotnet-issue-labeler dotnet-issue-labeler bot added the untriaged New issue has not been triaged by the area owner label May 15, 2021
@ghost
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ghost commented May 15, 2021

Tagging subscribers to this area: @carlossanlop
See info in area-owners.md if you want to be subscribed.

Issue Details

Description

When using a StreamWriter to write a file line by line, the beginning of the file is missing.

using System.IO;
using System.Linq;
using System.Text;

await using var writer = new StreamWriter("file.txt", append: false, Encoding.UTF8);
foreach (var url in Enumerable.Range(0, 1000).Select(i => "Line " + i))
{
    await writer.WriteLineAsync(url);
}

You can see that the file start at the middle of line 113:

image

Configuration

C:\Users\mezia>dotnet --info
.NET SDK (reflecting any global.json):
 Version:   6.0.100-preview.3.21202.5
 Commit:    aee38a6dd4

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.19042
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\6.0.100-preview.3.21202.5\

Host (useful for support):
  Version: 6.0.0-preview.3.21201.4
  Commit:  236cb21e3c

.NET SDKs installed:
  3.1.409 [C:\Program Files\dotnet\sdk]
  5.0.104 [C:\Program Files\dotnet\sdk]
  5.0.203 [C:\Program Files\dotnet\sdk]
  5.0.300-preview.21228.15 [C:\Program Files\dotnet\sdk]
  6.0.100-preview.3.21202.5 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.All 2.1.27 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.28 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.App 2.1.27 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.28 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.1.14 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.1.15 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 5.0.4 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 5.0.5 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 5.0.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 6.0.0-preview.3.21201.13 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 2.1.27 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.11 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.14 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.15 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 5.0.4 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 5.0.5 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 5.0.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 6.0.0-preview.3.21201.4 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 3.1.11 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 3.1.14 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 3.1.15 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 5.0.4 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 5.0.5 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 5.0.6 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 6.0.0-preview.3.21201.3 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Regression?

Yes, it works with .NET 5.0

Other information

It works well with WriteLine instead of WriteLineAsync. File.WriteAllLineAsync is also ok.

Author: meziantou
Assignees: -
Labels:

area-System.IO, untriaged
Milestone: -

@meziantou
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meziantou commented May 15, 2021 •
edited
Loading

Looking at the code, it seems the issue is because I'm using an encoding with a BOM. It seems _charPos is set to 0 before reading its value in Core when it emits the BOM:

runtime/src/libraries/System.Private.CoreLib/src/System/IO/StreamWriter.cs

Lines 944 to 946 in 8194ffb

Task flushTask = Core(flushStream, flushEncoder, cancellationToken);
_charPos = 0;

@meziantou meziantou mentioned this issue May 15, 2021
Merged
@ghost ghost added the in-pr There is an active PR which will close this issue when it is merged label May 15, 2021
@ghost ghost removed the in-pr There is an active PR which will close this issue when it is merged label May 26, 2021
@ghost ghost locked as resolved and limited conversation to collaborators Jun 25, 2021
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Fix FlushAsyncInternal when emitting BOM
2 participants
@vcsjones @meziantou