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Probably fine, need to merge the other first. |
This was referenced Jun 26, 2026
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nkolev92
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Jun 30, 2026
MSBuild 18.6 can run tasks in-process during parallel builds (dotnet build -mt / dotnet restore). Tasks opt in by carrying the [MSBuildMultiThreadableTask] marker attribute (Microsoft.Build.Framework). This applies the marker to the 12 NuGet restore tasks that are already thread-safe: they only read MSBuild item inputs and produce outputs, with no current-working-directory, environment-variable, ProcessStartInfo, or mutable-static usage. Tasks that resolve relative paths (e.g. GetRestoreProjectReferencesTask, GetRestoreSolutionProjectsTask) are intentionally left out; they need the TaskEnvironment migration first. To avoid conditional compilation at every task, a self-defined compatibility shim of the attribute is added for the .NET Framework build only (Common/MSBuildMultiThreadableTaskAttribute.cs, guarded by #if NETFRAMEWORK). The .NET (SDK) build uses the real attribute from the Microsoft.Build.Framework 18.6.3 package. MSBuild detects this attribute by namespace and name only (ignoring the defining assembly), so the shim is recognized by 18.6+ hosts and ignored by older ones. The shim is also compiled into NuGet.Build.Tasks.Pack because it shares GetProjectTargetFrameworksTask. Multithreaded mode is currently experimental and CLI-only; Visual Studio still runs tasks out of process, so the marker is a safe no-op there today. Tasks marked: GetRestoreDotnetCliToolsTask, GetProjectTargetFrameworksTask, GetRestorePackageReferencesTask, GetCentralPackageVersionsTask, GetRestorePackageDownloadsTask, GetRestoreFrameworkReferencesTask, GetRestoreNuGetAuditSuppressionsTask, GetRestorePrunePackageReferencesTask, CheckForDuplicateNuGetItemsTask, NuGetMessageTask, GetGlobalPropertyValueTask, GetReferenceNearestTargetFrameworkTask. Reference: https://learn.microsoft.com/visualstudio/msbuild/update-task-multithreaded Part of NuGet/Home#14958. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Bug
Fixes: addresses the trivial case of part 3 NuGet/Home#14958
Description
These tasks are stateless so they can be used in multithreaded msbuild execution without changes.
polyfill the attribute to net472 where we're not consuming the new MSBuild API
on top of #7508
PR Checklist
Added testsLink to an issue or pull request to update docs if this PR changes settings, environment variables, new feature, etc.