[8.0-preview2] error MSB4012: The expression "CompileListCount=@(_ReadyToRunCompileList->Count())" cannot be used in this context

[MichaelSimons]

The bootstrap leg of source-build is failing in 8.0 preview2 with the following error:

/repos/dotnet2/src/runtime/artifacts/source-build/self/src/artifacts/bin/Crossgen2Tasks/Debug/net8.0/Microsoft.NET.CrossGen.targets(349,49): error MSB4012: The expression "CompileListCount=@(_ReadyToRunCompileList->Count())" cannot be used in this context. Item lists cannot be concatenated with other strings where an item list is expected. Use a semicolon to separate multiple item lists. [/repos/dotnet2/src/runtime/artifacts/source-build/self/src/src/installer/pkg/sfx/Microsoft.NETCore.App/Microsoft.NETCore.App.Runtime.Composite.sfxproj]

Binlog

This is a blocker for the preview2 release. Any help in diagnosing would be appreciated. TIA

cc @dotnet/crossgen-contrib

[trylek]

Hmm, it looks like @davidwrighton was the last person touching this project in

#52579

but it's not clear to me from the PR whether the problematic line

runtime/src/tasks/Crossgen2Tasks/Microsoft.NET.CrossGen.targets

Line 349 in 5e3dd8d

<AllowEmptyTelemetry EventName="ReadyToRun" EventData="PublishReadyToRunUseCrossgen2=$(PublishReadyToRunUseCrossgen2);Crossgen2PackVersion=%(ResolvedCrossgen2Pack.NuGetPackageVersion);CompileListCount=@(_ReadyToRunCompileList->Count());FailedCount=@(_ReadyToRunCompilationFailures->Count())" />

was authored by him or not. If I understand the error message properly, MSBuild has a valid point that such a compound argument cannot be unambiguously parsed as the semicolon separator is used in two different contexts - to separate key=value pairs and multiple values. I have no idea how that was supposed to work.

[trylek]

/cc @hoyosjs who might be familiar with telemetry implementation

[MichaelSimons]

For clarity in the bootstrap build, we are using a source-built preview 2 sdk/toolset to rebuild source-build with. It is possible this is a new msbuild check.

[trylek]

/cc @rainersigwald for additional feedback regarding MSBuild functionality in the presence of the above clause

[rainersigwald]

This is not a new check and I don't think we've touched it recently.

[rainersigwald]

It's firing now because of dotnet/sdk#30269. @baronfel, that puts MSBuild in "you must want a list of items" mode, so an item transform complains when there's stuff around it. In this specific case preamble_@(Foo->Count())_suffix the concatenation is completely fine and wouldn't result in problems but our analysis isn't deep enough to see that.

[MichaelSimons]

@rainersigwald - is there a workaround we can apply in source-build to unblock us while a long term solution is discussed/implemented?

[trylek]

I'm glad to hear that, while I apparently completely misdiagnosed the issue, I have managed to pull in the right people :-).

[trylek]

@rainersigwald / @baronfel - the PR dotnet/sdk#30269 is apparently against a .NET 7 servicing branch unless I'm mistaken, do you know whether the equivalent fix has been merged into SDK main?

[MichaelSimons]

@rainersigwald / @baronfel - the PR dotnet/sdk#30269 is apparently against a .NET 7 servicing branch unless I'm mistaken, do you know whether the equivalent fix has been merged into SDK main?

Yes, changes made in the sdk servicing branches automatically flow into main. It flowed into main with dotnet/sdk#30645.

[trylek]

For a possible workaround, if I understand Rainer's explanation correctly, it should be possible to split the construction of the AllowEmptyTelemetry property into several parts, in particular we should be able to isolate the Count() computation by using it to populate an auxiliary property we would subsequently merge with the rest.

[baronfel]

So I believe the fix here is for runtime to use this factoring of the new item-based pattern:

	<ItemGroup>
       <_R2RCrossgenTelemetry Include="PublishReadyToRunUseCrossgen2" Value="$(PublishReadyToRunUseCrossgen2)" />
       <_R2RCrossgenTelemetry Include="Crossgen2PackVersion" Value="%(ResolvedCrossgen2Pack.NuGetPackageVersion)" />
       <_R2RCrossgenTelemetry Include="CompileListCount" Value="@(_ReadyToRunCompileList->Count())" />
       <_R2RCrossgenTelemetry Include="FailedCount" Value="@(_ReadyToRunCompilationFailures->Count())" />
    </ItemGroup>
    <AllowEmptyTelemetry EventName="ReadyToRun" EventData="@(_R2RCrossgenTelemetry)" />

Apologies for this - I fixed all the callsites in the SDK itself, but I must have missed this one and/or it changed after the fix flowed forwards.

[trylek]

@baronfel - just to satisfy my curiosity, do you happen to know who is consuming the AllowEmptyTelemetry property? I mean, I can imagine a parser that can do A=B;C;D;E=F;G but it must be a pretty sophisticated parser so I'm wondering whether we might be just dropping some of these key-value items on the floor unless it's specifically aware of this peculiar detail.