Fix SQL polyglot AppHost test restore environment

tests/CommunityToolkit.Aspire.Hosting.SqlDatabaseProjects.Tests/GoAppHostTests.cs

@@ -7,11 +7,11 @@ public class GoAppHostTests
     [Fact]
     public async Task GoAppHostCompiles()
     {
-        await GoAppHostTest.Run(
+        await SqlPolyglotAppHostTest.Run(() => GoAppHostTest.Run(
             appHostProject: "CommunityToolkit.Aspire.Hosting.SqlDatabaseProjects.AppHost.Go",
             exampleName: "sql-database-projects",
             // The prebuilt Windows AppHost server fails to load hostfxr for MSBuildLocator.
             validatePublish: !OperatingSystem.IsWindows(),
-            cancellationToken: TestContext.Current.CancellationToken);
+            cancellationToken: TestContext.Current.CancellationToken));
     }
 }

tests/CommunityToolkit.Aspire.Hosting.SqlDatabaseProjects.Tests/SqlPolyglotAppHostTest.cs

@@ -0,0 +1,35 @@
+namespace CommunityToolkit.Aspire.Hosting.SqlDatabaseProjects.Tests;
+
+internal static class SqlPolyglotAppHostTest
+{
+    private static readonly string[] s_msbuildEnvironmentVariables =
+    [
+        "MSBUILD_EXE_PATH",
+        "MSBuildExtensionsPath",
+        "MSBuildSDKsPath"
+    ];
+
+    public static async Task Run(Func<Task> test)
+    {
+        // MSBuildLocator in other SQL tests configures in-process MSBuild; child dotnet builds
+        // must select their own SDK instead of inheriting those paths.
+        Dictionary<string, string?> originalValues = s_msbuildEnvironmentVariables.ToDictionary(
+            name => name, Environment.GetEnvironmentVariable);
+        try
+        {
+            foreach (string name in s_msbuildEnvironmentVariables)
+            {
+                Environment.SetEnvironmentVariable(name, null);
+            }
+
+            await test();
+        }
+        finally
+        {
+            foreach ((string name, string? value) in originalValues)
+            {
+                Environment.SetEnvironmentVariable(name, value);
+            }
+        }
+    }
+}

tests/CommunityToolkit.Aspire.Hosting.SqlDatabaseProjects.Tests/SqlPolyglotAppHostTestTests.cs

@@ -0,0 +1,40 @@
+namespace CommunityToolkit.Aspire.Hosting.SqlDatabaseProjects.Tests;
+
+public class SqlPolyglotAppHostTestTests
+{
+    [Fact]
+    public async Task RestoresMSBuildEnvironmentAfterFailure()
+    {
+        string[] variables = ["MSBUILD_EXE_PATH", "MSBuildExtensionsPath", "MSBuildSDKsPath"];
+        Dictionary<string, string?> originalValues = variables.ToDictionary(name => name, Environment.GetEnvironmentVariable);
+        try
+        {
+            foreach (string variable in variables)
+            {
+                Environment.SetEnvironmentVariable(variable, "test-sdk-path");
+            }
+
+            await Assert.ThrowsAsync<InvalidOperationException>(() => SqlPolyglotAppHostTest.Run(() =>
+            {
+                foreach (string variable in variables)
+                {
+                    Assert.Null(Environment.GetEnvironmentVariable(variable));
+                }
+
+                throw new InvalidOperationException();
+            }));
+
+            foreach (string variable in variables)
+            {
+                Assert.Equal("test-sdk-path", Environment.GetEnvironmentVariable(variable));
+            }
+        }
+        finally
+        {
+            foreach ((string variable, string? value) in originalValues)
+            {
+                Environment.SetEnvironmentVariable(variable, value);
+            }
+        }
+    }
+}

tests/CommunityToolkit.Aspire.Hosting.SqlDatabaseProjects.Tests/TypeScriptAppHostTests.cs

@@ -9,11 +9,11 @@ public class TypeScriptAppHostTests
     [Fact]
     public async Task TypeScriptAppHostCompilesAndStarts()
     {
-        await TypeScriptAppHostTest.Run(
+        await SqlPolyglotAppHostTest.Run(() => TypeScriptAppHostTest.Run(
             appHostProject: "CommunityToolkit.Aspire.Hosting.SqlDatabaseProjects.AppHost.TypeScript",
             packageName: "CommunityToolkit.Aspire.Hosting.SqlDatabaseProjects",
             exampleName: "sql-database-projects",
             waitForResources: [],
-            cancellationToken: TestContext.Current.CancellationToken);
+            cancellationToken: TestContext.Current.CancellationToken));
     }
 }