CopyIfNewer file created by prebuild step is not copied until subsequent build

[rainersigwald]

From @loop-evgeny on February 2, 2018 17:12

I have a config file in my project (instance.config) that I want copied to the output directory, so it's set to "Copy if newer". This config file is not checked into source control, but there is a file (instance.config.template), which gets copied to instance.config if that doesn't already exist. This all works, but not in the same build: the first build copies instance.config to the source directory and only the next build copies it to the output. As it's the pre-build step, I would expect any files it generates to be treated like any other source files, so in this case, instance.config should be copied to the output by the first build after a clean checkout.

CopySourceFileInPreBuild.zip reproduces the problem.

I even tried getting the pre-build step to modify another source file, but that doesn't help.

A workaround is to create a post-build step to copy the file to the output instead of relying on the build system to do it, but a downside to this is that the project then gets built every time. For a large project this can be a major problem.

Copied from original issue: dotnet/project-system#3216

[rainersigwald]

From @Pilchie on February 2, 2018 18:30

Adding @rainersigwald. This is really an MSBuild question. I think the answer this that you need to put your "Copy" inside a target, because otherwise evaluation happens at the beginning of the build, before the pre-build step, and therefore before the file exists.

[rainersigwald]

I'm actually going to move this to the SDK, because it's the implicit None item that's causing the confusion.

[rainersigwald]

The repro project defines

  <ItemGroup>
    <None Update="instance.config">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
  </ItemGroup>

But there's nothing to update if the SDK's implicit None glob expansion doesn't catch the instance.config file, which it won't the first time through because it doesn't exist.

I would recommend using an explicit reference to the file instead. You can do this either by disabling the None glob and adding the item explicitly:

diff --git a/CopySourceFileInPreBuild.csproj b/CopySourceFileInPreBuild.csproj
index 58a2f1e..6fc644f 100644
--- a/CopySourceFileInPreBuild.csproj
+++ b/CopySourceFileInPreBuild.csproj
@@ -3,6 +3,7 @@
   <PropertyGroup>
     <OutputType>Exe</OutputType>
     <TargetFramework>netcoreapp2.0</TargetFramework>
+    <EnableDefaultNoneItems>false</EnableDefaultNoneItems>
   </PropertyGroup>
 
   <Target Name="PreBuild" BeforeTargets="PreBuildEvent">
@@ -10,7 +11,7 @@
   </Target>
 
   <ItemGroup>
-    <None Update="instance.config">
+    <None Include="instance.config">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </None>
   </ItemGroup>

or by removing the item that may or may not be created by the glob and explicitly adding a new one:

diff --git a/CopySourceFileInPreBuild.csproj b/CopySourceFileInPreBuild.csproj
index 58a2f1e..fb53299 100644
--- a/CopySourceFileInPreBuild.csproj
+++ b/CopySourceFileInPreBuild.csproj
@@ -10,7 +10,8 @@
   </Target>
 
   <ItemGroup>
-    <None Update="instance.config">
+    <None Remove="instance.config" />
+    <None Include="instance.config">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </None>
   </ItemGroup>

[loop-evgeny]

I tried the second version (explicit include) and it works - thanks a lot!

This is, of course, completely non-obvious to the user. How about having VS always explicitly include a file for which a user has CopyToOutputDirectory to PreserveNewest or CopyAlways? I believe that, in projects before .NET Core, a build would fail if a file like this didn't exist and this is what I would expect. Right now the setting, as it turns out, means something more like "copy if the source file exists". I'm not sure that's really a useful setting, but if it is, maybe that can be another explicit value.

[github-actions]

Due to lack of recent activity, this issue has been labeled as 'stale'. It will be closed if no further activity occurs within 30 more days. Any new comment will remove the label.

[loop-evgeny]

I can no longer repro with the original project attached to this issue using SDK 8.0.204, so this seems to have been fixed at some point!