Caching issues with ReadyToRun images

ReadyToRun images from a previous build can currently be reused when they should not.

Here’s what contributes to the issue:

• The _CreateR2RImages target compares file timestamps: as long as the input file has an earlier timestamp than the R2R file, the R2R file will not be regenerated.
• NuGet uses the timestamps from the nupkg when restoring packages, which means files from a newly restored package will have an earlier timestamp. But changing that wouldn’t help much, as a given package can already be present in the package cache.
• The Clean target does not clean the R2R images

This means that you will end up with an outdated R2R image if you update a NuGet package and then republish the project, unless you delete the obj directory manually first.

Here’s how to reproduce this:

dotnet new console
dotnet add package Newtonsoft.Json -v 11.0.2
dotnet publish -r win-x64 -p:PublishReadyToRun=true
dotnet add package Newtonsoft.Json -v 12.0.3
dotnet publish -r win-x64 -p:PublishReadyToRun=true

The Newtonsoft.Json.dll in the publish output will be the v11.0.2 version instead of v12.0.3. Inserting dotnet clean -r win-x64 after the first publish does not help.

To recap, I see two issues:

• R2R images should be invalidated when the source assembly is modified, using something stronger than just the file timestamp
• The Clean target should delete the R2R images

[ltrzesniewski]

Here’s a workaround I’m using, maybe it can help you too:

<!-- Work around https://github.com/dotnet/sdk/issues/12379 -->
<Target Name="DeleteR2RImages" BeforeTargets="_PrepareForReadyToRunCompilation" Condition="'$(PublishReadyToRun)' == 'true'">
  <PropertyGroup>
    <_R2RDirToRemove>$(IntermediateOutputPath)R2R</_R2RDirToRemove>
  </PropertyGroup>
  <RemoveDir Directories="$(_R2RDirToRemove)" />
</Target>

This basically clears the R2R cache before each publish, so it’s not great, but it’s still better than getting a broken build.

It works on the 3.1 SDK. I haven’t tested it on .NET 5 yet but from a quick glance at the source, it should still work.

[kostazol]

The same problem was and exists in the old .Net Framework when I enable PrecompileBeforePublish - it publishes not a max version of NuGet packages, but these versions were used in another branch, and in VS I see the project used the previous versions of packages.