dotnet publish fails for web project when web.config is read-only

Publishing a web project fails when a web.config exists and is readonly, when running Windows. This causes problems, because I sometimes use Perforce as a code repository, and Perforce works best if I let it keep its unchanged files in read-only state.

Steps to reproduce:

> mkdir PublishProblem
> pushd PublishProblem
> dotnet new mvc
> dotnet publish 
[No errors]
> dotnet new webconfig
> dotnet publish
[No errors]
> attrib +R web.config
> dotnet publish
Microsoft (R) Build Engine version 16.8.0+126527ff1 for .NET
Copyright (C) Microsoft Corporation. All rights reserved.

  Determining projects to restore...
  All projects are up-to-date for restore.
  PublishProblem -> C:\Development\PublishProblem\bin\Debug\net5.0\PublishProblem.dll
  PublishProblem -> C:\Development\PublishProblem\bin\Debug\net5.0\PublishProblem.Views.dll
  PublishProblem -> C:\Development\PublishProblem\bin\Debug\net5.0\publish\
C:\Program Files\dotnet\sdk\5.0.101\Sdks\Microsoft.NET.Sdk.Publish\targets\TransformTargets\Microsoft.NET.Sdk.Publish.TransformFiles.targets(50,5): error MSB4018: The "TransformWebConfig" task failed unexpectedly. [C:\Development\PublishProblem\PublishProblem.csproj]
C:\Program Files\dotnet\sdk\5.0.101\Sdks\Microsoft.NET.Sdk.Publish\targets\TransformTargets\Microsoft.NET.Sdk.Publish.TransformFiles.targets(50,5): error MSB4018: System.UnauthorizedAccessException: Access to the path 'C:\Development\PublishProblem\bin\Debug\net5.0\publish\web.config' is denied. [C:\Development\PublishProblem\PublishProblem.csproj]
C:\Program Files\dotnet\sdk\5.0.101\Sdks\Microsoft.NET.Sdk.Publish\targets\TransformTargets\Microsoft.NET.Sdk.Publish.TransformFiles.targets(50,5): error MSB4018:    at System.IO.FileStream.ValidateFileHandle(SafeFileHandle fileHandle) [C:\Development\PublishProblem\PublishProblem.csproj]
C:\Program Files\dotnet\sdk\5.0.101\Sdks\Microsoft.NET.Sdk.Publish\targets\TransformTargets\Microsoft.NET.Sdk.Publish.TransformFiles.targets(50,5): error MSB4018:    at System.IO.FileStream.CreateFileOpenHandle(FileMode mode, FileShare share, FileOptions options) [C:\Development\PublishProblem\PublishProblem.csproj]
C:\Program Files\dotnet\sdk\5.0.101\Sdks\Microsoft.NET.Sdk.Publish\targets\TransformTargets\Microsoft.NET.Sdk.Publish.TransformFiles.targets(50,5): error MSB4018:    at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options) [C:\Development\PublishProblem\PublishProblem.csproj]
C:\Program Files\dotnet\sdk\5.0.101\Sdks\Microsoft.NET.Sdk.Publish\targets\TransformTargets\Microsoft.NET.Sdk.Publish.TransformFiles.targets(50,5): error MSB4018:    at System.IO.FileStream..ctor(String path, FileMode mode) [C:\Development\PublishProblem\PublishProblem.csproj]
C:\Program Files\dotnet\sdk\5.0.101\Sdks\Microsoft.NET.Sdk.Publish\targets\TransformTargets\Microsoft.NET.Sdk.Publish.TransformFiles.targets(50,5): error MSB4018:    at Microsoft.NET.Sdk.Publish.Tasks.TransformWebConfig.Execute() [C:\Development\PublishProblem\PublishProblem.csproj]
C:\Program Files\dotnet\sdk\5.0.101\Sdks\Microsoft.NET.Sdk.Publish\targets\TransformTargets\Microsoft.NET.Sdk.Publish.TransformFiles.targets(50,5): error MSB4018:    at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute() [C:\Development\PublishProblem\PublishProblem.csproj]
C:\Program Files\dotnet\sdk\5.0.101\Sdks\Microsoft.NET.Sdk.Publish\targets\TransformTargets\Microsoft.NET.Sdk.Publish.TransformFiles.targets(50,5): error MSB4018:    at Microsoft.Build.BackEnd.TaskBuilder.ExecuteInstantiatedTask(ITaskExecutionHost taskExecutionHost, TaskLoggingContext taskLoggingContext, TaskHost taskHost, ItemBucket bucket, TaskExecutionMode howToExecuteTask) [C:\Development\PublishProblem\PublishProblem.csproj]
>

Dotnet info:

> dotnet --info
.NET SDK (reflecting any global.json):
 Version:   5.0.101
 Commit:    d05174dc5a

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.17763
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\5.0.101\

Host (useful for support):
  Version: 5.0.1
  Commit:  b02e13abab

.NET SDKs installed:
  2.1.202 [C:\Program Files\dotnet\sdk]
  2.1.503 [C:\Program Files\dotnet\sdk]
  2.1.505 [C:\Program Files\dotnet\sdk]
  2.1.508 [C:\Program Files\dotnet\sdk]
  2.1.509 [C:\Program Files\dotnet\sdk]
  2.1.515 [C:\Program Files\dotnet\sdk]
  2.1.602 [C:\Program Files\dotnet\sdk]
  2.1.801 [C:\Program Files\dotnet\sdk]
  5.0.101 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.All 2.1.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.9 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.12 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.19 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.23 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.App 2.1.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.9 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.12 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.19 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.23 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.1.10 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 5.0.1 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 2.0.9 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.7 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.9 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.12 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.13 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.19 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.23 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.10 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 5.0.1 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 3.1.10 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 5.0.1 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

However, also reproduced with 5.0.100 earlier.

I have made a Windows-only workaround that I paste into Directory.Build.targets until the problem is fixed: https://gist.github.com/geirs73/e57539d8e8e20bcd98ad31d4758e0d67 It will remove the read-only attribute for a short while, while publishing, and then restore it.

> rmdir bin /s /q
> dotnet publish
Microsoft (R) Build Engine version 16.8.0+126527ff1 for .NET
Copyright (C) Microsoft Corporation. All rights reserved.

  Determining projects to restore...
  All projects are up-to-date for restore.
  PublishProblem -> C:\Development\PublishProblem\bin\Debug\net5.0\PublishProblem.dll
  PublishProblem -> C:\Development\PublishProblem\bin\Debug\net5.0\PublishProblem.Views.dll
  PublishProblem -> C:\Development\PublishProblem\bin\Debug\net5.0\publish\
  FIX: web.config is set to writable
  FIX: web.config is restored to read only
>

My guess is that the read-only flag is not cleared when a build step or the transform task is first copying the web.config to the publish directory, and then it croaks when trying to write to that web.config file under transform.

[JamesQMurphy]

This is also an issue for repositories that still use TFVC, where files are set to read-only during a “get latest” operation. I’m using a similar workaround in my build pipeline, where I am removing the read-only attribute from the web.config file prior to calling dotnet publish.

[geirs73]

The root cause of my issue may be located inside TransformWebConfig.cs, after further study and some experimentation on a local clone of 5.0.2xx branch. I changed Execute() so that it removes any ReadOnly attribute on the copied web.config file in the publish directory, and got a “works on my machine”. I do not know enough about the internal structure of this project to do a proper fix that is testable and guaranteed to work on any platform, but I hope it is helpful anyway.

diff --git a/src/WebSdk/Publish/Tasks/Tasks/TransformWebConfig.cs b/src/WebSdk/Publish/Tasks/Tasks/TransformWebConfig.cs
index 07b957dbe..56bb5bea9 100644
--- a/src/WebSdk/Publish/Tasks/Tasks/TransformWebConfig.cs
+++ b/src/WebSdk/Publish/Tasks/Tasks/TransformWebConfig.cs
@@ -89,6 +89,13 @@ public override bool Execute()
                 if (File.Exists(projectWebConfigPath))
                 {
                     File.Copy(projectWebConfigPath, publishWebConfigPath, true);
+                    FileAttributes publishWebConfigAttr = File.GetAttributes(publishWebConfigPath);
+
+                    if ((publishWebConfigAttr & FileAttributes.ReadOnly) == FileAttributes.ReadOnly)
+                    {
+                        publishWebConfigAttr = publishWebConfigAttr & ~FileAttributes.ReadOnly;
+                        File.SetAttributes(publishWebConfigPath, publishWebConfigAttr);
+                    }
                 }
                 else
                 {