Try MSBuild's /Isolate

[Youssef1313]

No description provided.

[Copilot]

Pull request overview

Adds an MSBuild auto-response file to enable MSBuild’s /Isolate behavior for builds in this repository.

Changes:

• Introduce Directory.Build.rsp with /Isolate so the flag is applied automatically to MSBuild invocations.

[Copilot]

The PR description is still the template/empty, but this change globally alters build behavior for the whole repo. Please update the PR description to include (1) why /Isolate is needed, (2) the expected user-facing impact (CLI build, VS build, CI), and (3) any measured improvement/regression you observed.

[Copilot]

Adding /Isolate via Directory.Build.rsp applies it to all MSBuild executions (including local dev builds and IDE-driven builds), and may fail on environments where the MSBuild version doesn’t recognize the switch. If the intent is CI-only or limited-scope usage, consider moving this flag into the CI/build scripts instead of Directory.Build.rsp; otherwise, pin/standardize the build toolchain (e.g., via global.json and CI image/tooling updates) so all supported environments use an MSBuild version that supports /Isolate.

Suggested change

	/Isolate
	# /Isolate flag removed from global response file.
	# If isolation is required, pass /Isolate explicitly from CI or build scripts
	# instead of applying it to all MSBuild invocations via Directory.Build.rsp.

[Youssef1313]

@ViktorHofer We wanted to test if this can give us some perf improvement during build, but looks like we cannot do that today when using Arcade?

.packages/microsoft.dotnet.arcade.sdk/11.0.0-beta.26173.2/tools/Build.proj(176,5): error : MSB4254: The MSBuild task is building project(s) ""/mnt/vss/_work/1/s/.packages/microsoft.dotnet.arcade.sdk/11.0.0-beta.26173.2/tools/Tools.proj"" which are not specified in the ProjectReference item. In isolated builds this probably means that the references are not explicitly specified as a ProjectReference item in "/mnt/vss/_work/1/s/.packages/microsoft.dotnet.arcade.sdk/11.0.0-beta.26173.2/tools/Build.proj" /mnt/vss/_work/1/s/.packages/microsoft.dotnet.arcade.sdk/11.0.0-beta.26173.2/tools/Build.proj

Any recommendation? Or should we simply abandon this idea?

[ViktorHofer]

Yeah Arcade seems to be in-compatible with /graph or /isolate. You could try to change that though. Additionally, you could also always experiment with just building the repo with dotnet build directly instead of going through eng/common/build.cmd/sh.

[Youssef1313]

Closing for now. Not planned to be investigated soon-ish.