From 5e969452c6453a60ed4f818e7b4a2ff5ffc8963a Mon Sep 17 00:00:00 2001
From: Benjamin Michaelis <git@relay.benjamin.michaelis.net>
Date: Thu, 14 May 2026 08:37:42 -0700
Subject: [PATCH] Fix MSB3491 race condition in WriteLaunchers parallel builds

Write build variables to \ (per-project output directory)
instead of a shared global temp path. Multiple projects building in
parallel each get their own unique output directory, eliminating the
delete-then-create race on the shared temp file.

Update the RepositoryPaths.BuildVariables reader to use
AppContext.BaseDirectory instead of Path.GetTempPath(), since the
.tmp file now lives alongside the built assembly. AppContext.BaseDirectory
is AOT-safe and correctly resolves in Live Unit Testing scenarios.

Remove the now-unnecessary TempStagingPath property and collapse the
two conditional WriteLinesToFile calls into one unconditional write.
---
 IntelliTect.Multitool.AotTest/Program.cs                  | 2 +-
 IntelliTect.Multitool/Build/IntelliTect.Multitool.targets | 4 +---
 IntelliTect.Multitool/RepositoryPaths.cs                  | 2 +-
 3 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/IntelliTect.Multitool.AotTest/Program.cs b/IntelliTect.Multitool.AotTest/Program.cs
index 0d040c2..e8ed701 100644
--- a/IntelliTect.Multitool.AotTest/Program.cs
+++ b/IntelliTect.Multitool.AotTest/Program.cs
@@ -20,7 +20,7 @@
     return 1;
 }
 
-// RepositoryPaths is excluded: its static initializer reads a build-time temp file
+// RepositoryPaths is excluded: its static initializer reads a build-time file from the output directory
 // that doesn't exist at AOT runtime. The class is AOT-compatible (file I/O + LINQ only).
 
 Console.WriteLine("AOT test passed.");
diff --git a/IntelliTect.Multitool/Build/IntelliTect.Multitool.targets b/IntelliTect.Multitool/Build/IntelliTect.Multitool.targets
index d366ba6..2ca85d3 100644
--- a/IntelliTect.Multitool/Build/IntelliTect.Multitool.targets
+++ b/IntelliTect.Multitool/Build/IntelliTect.Multitool.targets
@@ -24,7 +24,6 @@
 
     <Target Name="WriteLaunchers" AfterTargets="CopyFilesToOutputDirectory">
         <PropertyGroup>
-            <TempStagingPath Condition="'$(TempStagingPath)' == ''">$([System.IO.Path]::GetTempPath())</TempStagingPath>
             <LUTInformation>
                 BuildingForLiveUnitTesting::$(BuildingForLiveUnitTesting)
                 SolutionDir::$(SolutionDir)
@@ -32,7 +31,6 @@
             </LUTInformation>
         </PropertyGroup>
 
-        <WriteLinesToFile File="$(TempStagingPath)\IntelliTect.MultiTool.BuildVariables.tmp" Overwrite="true" Lines="$(LUTInformation)" Condition="'$(SolutionDir)' != ''" />
-        <WriteLinesToFile File="$(TempStagingPath)\IntelliTect.MultiTool.BuildVariables.tmp" Overwrite="true" Lines="$(LUTInformation)" Condition="'$(SolutionDir)' == '' AND !Exists('$(TempStagingPath)\IntelliTect.MultiTool.BuildVariables.tmp')" />
+        <WriteLinesToFile File="$(OutDir)IntelliTect.MultiTool.BuildVariables.tmp" Overwrite="true" Lines="$(LUTInformation)" />
     </Target>
 </Project>
diff --git a/IntelliTect.Multitool/RepositoryPaths.cs b/IntelliTect.Multitool/RepositoryPaths.cs
index 35db6a5..9327cec 100644
--- a/IntelliTect.Multitool/RepositoryPaths.cs
+++ b/IntelliTect.Multitool/RepositoryPaths.cs
@@ -15,7 +15,7 @@ public static class RepositoryPaths
     /// <summary>
     /// Holds the key value pairs of the build variables that this class can use.
     /// </summary>
-    public static ReadOnlyDictionary<string, string?> BuildVariables { get; } = new(File.ReadAllLines(Path.Combine(Path.GetTempPath(), BuildVariableFileName))
+    public static ReadOnlyDictionary<string, string?> BuildVariables { get; } = new(File.ReadAllLines(Path.Combine(AppContext.BaseDirectory, BuildVariableFileName))
         .Select(line => line.Split("::"))
         .ToDictionary(split => split[0].Trim(),
         split => !string.IsNullOrEmpty(split[1]) ? split[1].Trim() : null));