Add workaround for SDK root drive casing issue by ViktorHofer · Pull Request #17002 · dotnet/arcade

ViktorHofer · 2026-06-11T09:50:02Z

To double check:

The right tests are in and the right validation has happened. Guidance: https://github.com/dotnet/arcade/blob/main/Documentation/Validation.md

Copilot

Pull request overview

Adds a Windows-specific workaround in Arcade SDK MSBuild targets to normalize $(NetCoreSdkRoot) drive-letter casing early in the build, mitigating task-host handshake failures caused by casing-sensitive salt computation.

Changes:

Adds InitialTargets="NormalizeNetCoreSdkRootCasing" to ensure normalization runs at the start of each project build.
Introduces an inline RoslynCodeTaskFactory task that probes canonical drive-letter casing via LoadLibraryExW + GetModuleFileNameW and rewrites only the drive letter.
Adds a NormalizeNetCoreSdkRootCasing target that updates the NetCoreSdkRoot property on Windows.

Show a summary per file

File	Description
src/Microsoft.DotNet.Arcade.Sdk/tools/Workarounds.targets	Adds a new Windows-only target + inline task to normalize `NetCoreSdkRoot` drive casing and wires it via `InitialTargets`.

Copilot's findings

Tip

Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

Files reviewed: 1/1 changed files
Comments generated: 3

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

Copilot

Copilot's findings

Files reviewed: 1/1 changed files
Comments generated: 1

Copilot

Copilot's findings

Files reviewed: 1/1 changed files
Comments generated: 2

The previous LoadLibraryEx(LOAD_LIBRARY_AS_DATAFILE)+GetModuleFileName(hModule) technique was a silent no-op: GetModuleFileName returns ERROR_MOD_NOT_FOUND for an image loaded only as a data file (the SDK's MSBuild.exe/MSBuild.dll are not otherwise loaded in the VS MSBuild process), so the casing was never fixed and MSB4216 persisted (verified in build 2998220). Open the SDK root directory with CreateFileW(FILE_FLAG_BACKUP_SEMANTICS) and ask the OS for its canonical path via GetFinalPathNameByHandleW. This is load- and bitness-independent. Splice only the canonical drive letter, and only when the rest of the path is otherwise case-insensitively identical, so symlink/junction resolution (which GetFinalPathNameByHandle performs but the child's Environment.ProcessPath does not) cannot desync the two salts. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Make the temporary #14026 workaround leave visible evidence in CI console logs (it only fires when the drive casing actually differs, so this is not noisy on healthy machines). Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Copilot's findings

Files reviewed: 1/1 changed files
Comments generated: 2

NetCoreSdkRoot carries a trailing directory separator, but GetFinalPathNameByHandle returns the canonical path without one. The strict full-path equality guard therefore always failed, making the drive-casing normalization a silent no-op and leaving MSB4216 (#14026) unfixed. Compare with trailing separators trimmed from both sides. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

JanProvaznik

please avoid RoslynCodeTaskFactory. that'll make it difficult to get to the "0 nonmigrated tasks" for -mt testing on arcade-built repos

…builds on #17002) (#17039) Co-authored-by: Viktor Hofer <7412651+ViktorHofer@users.noreply.github.com> Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com> Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

ViktorHofer · 2026-06-29T08:14:55Z

Closing as #17039 got merged.

please avoid RoslynCodeTaskFactory.

@JanProvaznik we do depend on using RoslynCodeTaskFactory for applying workarounds quickly in Arcade. Rainer did the same when we had an msbuild regression around loading System.Text.Json in the past.

…ing (#14027) ### Context A .NET Framework MSBuild host (e.g. VS) launching the .NET SDK task host can fail the handshake with: ``` error MSB4216: Could not run the "..." task because MSBuild could not create or connect to a task host with runtime "NET" and architecture "x86". ``` The handshake **salt** is a case-sensitive hash of the SDK tools directory. For the **.NET task host** the two sides derive that directory string differently: - **Host** (.NET Framework MSBuild) passes the tools directory derived from the `$(NetCoreSdkRoot)` property, whose drive-letter casing is propagated verbatim from the environment (e.g. an Azure DevOps `D:\a\_work\1\s` sources path) and is never canonicalized. - **Child** (.NET task host) resolves its own path via `Environment.ProcessPath` (`GetModuleFileNameW`), which on these agents reports a **lowercase** drive letter. When those casings differ (proven from the failing build''s comm traces: host `D:\...\sdk\11.0.100-preview.5...` vs child `d:\...\sdk\11.0.100-preview.5...`, salts `-1569896665` vs `-930293759`) the salts differ and the handshake fails. Because the NET task host uses a sentinel version (`99.99.99.99`), host and child can be different MSBuild builds, so both must agree on the salt input. ### Approach (child-side salt widening) The child validates the salt, so the fix **widens what the child accepts**: when the received salt does not match, the .NET task host child also accepts the salt computed from its tools directory with the **opposite drive-letter casing**. Both spellings denote the same directory on Windows, so this only **adds** an accepted value. This is the only approach that is provably **non-regressing**: - It is **monotonic** — the child accepts a superset of salts, so no host that connects successfully today can ever be rejected. There is no salt **value** change, hence no version-skew flag-day. - The added value denotes the **same** SDK directory, so node-reuse isolation is preserved (a genuinely different tools directory is still rejected — covered by a unit test). - It needs **no Arcade workaround** and **no VS change**: it fixes any VS-host / updated-SDK-child pairing as soon as the SDK carries this change. Scope is limited to the `Runtime="NET"` task host path (`IsNetTaskHost`); other node types and the CLR2 task host are untouched. The only pairing this cannot fix is an **already-shipped old SDK** child — no host change can alter how an old child hashes its own path. Customers get the fix by moving to an SDK that contains it. ### Why the previous host-side approach was abandoned The earlier revision normalized the launch path on the host with `GetFinalPathNameByHandle`, which **always returns an uppercase drive letter**. That matched neither direction reliably: it was a no-op for an already-uppercase host path (exactly the failing build), could not match a child whose loader-resolved path used a lowercase drive, and risked regressing configurations whose working casing was lowercase. The same uppercasing is also why the Arcade workaround (dotnet/arcade#17002) silently no-op''d. ### Changes Made - `src/Framework/BackEnd/Handshake.cs`: for the .NET task host, precompute the salt for the tools directory with the opposite drive-letter casing (`_netTaskHostSaltDriveCaseVariant`) and expose `IsNetTaskHostSaltMatch`. Helper `TryGetDriveLetterCaseVariant` returns false off-Windows and for driveless/UNC paths, so non-Windows and non-drive cases are unchanged. - `src/Shared/NodeEndpointOutOfProcBase.cs`: in the child''s `IsHandshakePartValid`, add a `Salt` case inside the existing `#if NET` NET-task-host allowance block that accepts the drive-case variant. - `src/Build.UnitTests/BackEnd/AppHostSupport_Tests.cs`: three Windows-only tests — accepts the drive-casing variant, rejects an unrelated SDK directory (isolation preserved), and confirms non-NET-task-host nodes do not widen acceptance. - The previous host-side canonicalization in `NodeProviderOutOfProcTaskHost.cs` and the `GetFinalPathNameByHandle` entry in `NativeMethods.txt` are **reverted**. ### Testing - `Handshake_NetTaskHost_AcceptsDriveLetterCasingDifference`, `Handshake_NetTaskHost_RejectsUnrelatedToolsDirectory`, `Handshake_NonNetTaskHost_DoesNotWidenSaltAcceptance` — pass (net10.0). - Existing `Handshake_ExternalPathCanMismatch_DefaultAlwaysMatches` — still passes (no regression). - Engine, MSBuild, MSBuildTaskHost and the test project build clean (0 warnings). ### Notes - See #14026 for the full root-cause analysis and the comm-trace / binlog evidence. - No new warnings or errors are introduced, so this is safe under `/WarnAsError`; no Change Wave is needed (pure compatibility widening). --------- Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com> Co-authored-by: Jan Provazník <janprovaznik@microsoft.com>

Add workaround for SDK root drive casing issue

a00475d

Copilot AI review requested due to automatic review settings June 11, 2026 09:50

Copilot started reviewing on behalf of ViktorHofer June 11, 2026 09:50 View session

Copilot AI reviewed Jun 11, 2026

View reviewed changes

Comment thread src/Microsoft.DotNet.Arcade.Sdk/tools/Workarounds.targets Outdated

Comment thread src/Microsoft.DotNet.Arcade.Sdk/tools/Workarounds.targets

Comment thread src/Microsoft.DotNet.Arcade.Sdk/tools/Workarounds.targets Outdated

Potential fix for pull request finding

c7e87d6

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

Copilot AI review requested due to automatic review settings June 11, 2026 10:02

Potential fix for pull request finding

d42487d

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

Copilot started reviewing on behalf of ViktorHofer June 11, 2026 10:02 View session

ViktorHofer and others added 3 commits June 11, 2026 12:02

Potential fix for pull request finding

1870324

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

Update conditions for NormalizeSdkRootDriveCasing task

7fd82d0

Fix condition syntax in Workarounds.targets

ae6747d

Copilot AI reviewed Jun 11, 2026

View reviewed changes

Comment thread src/Microsoft.DotNet.Arcade.Sdk/tools/Workarounds.targets

ViktorHofer mentioned this pull request Jun 11, 2026

MSB4216: .NET task host handshake fails due to case-sensitive drive-letter casing in salt (VS 18.6 + .NET 11 SDK) dotnet/msbuild#14026

Open

Update Workarounds.targets

57ae827

Copilot AI review requested due to automatic review settings June 11, 2026 10:04

Copilot started reviewing on behalf of ViktorHofer June 11, 2026 10:04 View session

ViktorHofer mentioned this pull request Jun 11, 2026

Fix NET task host MSB4216 handshake failure via child-side salt widening dotnet/msbuild#14027

Merged

Copilot AI reviewed Jun 11, 2026

View reviewed changes

Comment thread src/Microsoft.DotNet.Arcade.Sdk/tools/Workarounds.targets

Comment thread src/Microsoft.DotNet.Arcade.Sdk/tools/Workarounds.targets

ViktorHofer and others added 2 commits June 12, 2026 09:41

Copilot AI review requested due to automatic review settings June 12, 2026 09:21

Copilot started reviewing on behalf of ViktorHofer June 12, 2026 09:21 View session

Copilot AI reviewed Jun 12, 2026

View reviewed changes

Comment thread src/Microsoft.DotNet.Arcade.Sdk/tools/Workarounds.targets

Comment thread src/Microsoft.DotNet.Arcade.Sdk/tools/Workarounds.targets

This was referenced Jun 23, 2026

Fix #14026 NET task host MSB4216 via dotnet-host drive-casing probe (builds on #17002) #17039

Merged

Work around MSB4216 NET task host drive-casing failure in CodeQL build microsoft/testfx#9371

Closed

JanProvaznik requested changes Jun 23, 2026

View reviewed changes

AlesProkop mentioned this pull request Jun 25, 2026

Remove the temporary NetCoreSdkRoot drive-casing MSB4216 workaround once the msbuild fix reaches the supported VS + SDK floor (#17039) #17052

Open

ViktorHofer closed this Jun 29, 2026

ViktorHofer deleted the ViktorHofer-patch-2 branch June 29, 2026 08:15

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

Add workaround for SDK root drive casing issue#17002

Add workaround for SDK root drive casing issue#17002
ViktorHofer wants to merge 10 commits into
mainfrom
ViktorHofer-patch-2

ViktorHofer commented Jun 11, 2026

Uh oh!

Copilot AI left a comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Copilot AI left a comment

Uh oh!

Uh oh!

Copilot AI left a comment

Uh oh!

Uh oh!

Uh oh!

Copilot AI left a comment

Uh oh!

Uh oh!

Uh oh!

JanProvaznik left a comment •

edited

Loading

Uh oh!

ViktorHofer commented Jun 29, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

Uh oh!

Conversation

ViktorHofer commented Jun 11, 2026

To double check:

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Copilot's findings

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Copilot's findings

Uh oh!

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Copilot's findings

Uh oh!

Uh oh!

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Copilot's findings

Uh oh!

Uh oh!

Uh oh!

JanProvaznik left a comment • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

ViktorHofer commented Jun 29, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

JanProvaznik left a comment •

edited

Loading