Fix connector cross-platform dotnet-host lookup and win-x64-hardcoded packaging

src/LSP/Reqnroll.IdeSupport.LSP.Connector/Connector/Connector.csproj

@@ -17,8 +17,13 @@
          connectors are automatically included in the VSIX without any Extension-side changes.
          AppContext.BaseDirectory at runtime is {vsix-install}\LSPServer\, and
          OutProcReqnrollConnector.GetConnectorsFolder() appends "Connectors\", so the
-         expected runtime path is LSPServer\Connectors\Reqnroll-Generic-{tfm}\. -->
-    <_OutputCopyLocation>$([System.IO.Path]::GetFullPath('$(MSBuildThisFileDirectory)..\..\Reqnroll.IdeSupport.LSP.Server\bin\$(Configuration)\net10.0\win-x64\Connectors\Reqnroll-Generic-$(TargetFramework)'))</_OutputCopyLocation>
+         expected runtime path is LSPServer\Connectors\Reqnroll-Generic-{tfm}\.
+         _ConnectorServerRid is passed in by Reqnroll.IdeSupport.LSP.Server.csproj's
+         BuildConnector target so the staged output lands next to whichever RID the
+         server itself is being built/published for (win-x64/linux-x64/osx-x64/osx-arm64);
+         it defaults to win-x64 for plain VS/VSIX builds that don't set it. -->
+    <_ConnectorServerRid Condition="'$(_ConnectorServerRid)' == ''">win-x64</_ConnectorServerRid>
+    <_OutputCopyLocation>$([System.IO.Path]::GetFullPath('$(MSBuildThisFileDirectory)..\..\Reqnroll.IdeSupport.LSP.Server\bin\$(Configuration)\net10.0\$(_ConnectorServerRid)\Connectors\Reqnroll-Generic-$(TargetFramework)'))</_OutputCopyLocation>
     <NoWarn>NETSDK1138;NETSDK1233;MSB3277</NoWarn>
     <SuppressTfmSupportBuildWarnings>true</SuppressTfmSupportBuildWarnings>
     <!--

src/LSP/Reqnroll.IdeSupport.LSP.Server/Discovery/AssemblyReflection/OutProcReqnrollConnector.cs

@@ -187,7 +187,21 @@ protected string GetDotNetExecCommand(List<string> arguments, string executableF
         return GetDotNetCommand();
     }
 
-    private string GetDotNetCommand() => Path.Combine(GetDotNetInstallLocation(), "dotnet.exe");
+    private string GetDotNetCommand()
+    {
+        if (!OperatingSystem.IsWindows())
+            return ResolveNonWindowsDotNetCommand(Environment.GetEnvironmentVariable("DOTNET_ROOT"));
+
+        return Path.Combine(GetDotNetInstallLocation(), "dotnet.exe");
+    }
+
+    // No Windows-style Program Files layout on Linux/macOS. Prefer an explicit DOTNET_ROOT
+    // (set by the .NET install scripts / CI images); otherwise rely on "dotnet" being
+    // resolvable via PATH, which is the standard install on Linux/macOS.
+    // Extracted as a pure function (taking the env var value as a parameter) so it can be
+    // unit-tested without depending on the host OS actually being non-Windows.
+    internal static string ResolveNonWindowsDotNetCommand(string dotNetRoot) =>
+        string.IsNullOrEmpty(dotNetRoot) ? "dotnet" : Path.Combine(dotNetRoot, "dotnet");
 
     protected string GetConnectorsFolder()
     {

src/LSP/Reqnroll.IdeSupport.LSP.Server/Reqnroll.IdeSupport.LSP.Server.csproj

@@ -44,10 +44,17 @@
        pattern: it triggers the connector's outer build, which dispatches each TFM inner
        build and runs CustomAfterBuild (which stages the connector outputs into this
        project's Connectors\ output folder) before this project begins compiling. -->
+  <!-- RuntimeIdentifier/SelfContained are global properties: when the server itself is
+       published self-contained for a specific RID, MSBuild would otherwise leak those
+       into the connector's nested build below. The connector is always a
+       framework-dependent, per-TFM build regardless of which RID the server targets
+       (see docs on _ConnectorServerRid in Connector.csproj), so they're cleared here
+       and the RID is instead threaded through via _ConnectorServerRid, which only
+       affects where the build output is staged. -->
   <Target Name="BuildConnector" BeforeTargets="Build">
     <MSBuild Projects="$(MSBuildThisFileDirectory)..\Reqnroll.IdeSupport.LSP.Connector\Connector\Connector.csproj"
              Targets="Build"
-             Properties="Configuration=$(Configuration)" />
+             Properties="Configuration=$(Configuration);_ConnectorServerRid=$(RuntimeIdentifier);RuntimeIdentifier=;SelfContained=false" />
   </Target>
 
   <!-- Copy Connector binaries into the publish output so reflection-based binding

tests/LSP/Reqnroll.IdeSupport.LSP.Server.Tests/Discovery/GenericOutProcReqnrollConnectorTests.cs

@@ -67,7 +67,9 @@ public void GetConnectorPath_for_netcore_uses_dotnet_exec_with_the_matching_dll(
         var (path, args) = Resolve(tfm);
 
         // Launcher is the dotnet host; the connector dll is passed as an "exec" argument.
-        path.Should().EndWith("dotnet.exe");
+        // The host binary name is OS-dependent ("dotnet.exe" on Windows, "dotnet" elsewhere) -
+        // see OutProcReqnrollConnector.GetDotNetCommand / ResolveNonWindowsDotNetCommand.
+        path.Should().EndWith(OperatingSystem.IsWindows() ? "dotnet.exe" : "dotnet");
         args.Should().HaveCount(2);
         args[0].Should().Be("exec");
         args[1].Should().Be(Path.Combine(_extensionFolder, expectedRelative));
@@ -80,7 +82,7 @@ public void GetConnectorPath_defaults_to_net8_when_target_framework_has_no_versi
         // net8.0 default seeded at the top of GetConnectorPath.
         var (path, args) = Resolve(".NETCoreApp");
 
-        path.Should().EndWith("dotnet.exe");
+        path.Should().EndWith(OperatingSystem.IsWindows() ? "dotnet.exe" : "dotnet");
         args[1].Should().Be(Path.Combine(_extensionFolder, @"Reqnroll-Generic-net8.0\reqnroll-ide-connector.dll"));
     }
 }

tests/LSP/Reqnroll.IdeSupport.LSP.Server.Tests/Discovery/OutProcReqnrollConnectorTests.cs

@@ -64,4 +64,34 @@ public void RunDiscovery_stamps_the_connector_type_on_the_result()
         // GetConnectorType() strips the "OutProcReqnrollConnector" suffix from the type name.
         result.ConnectorType.Should().Be("Fake");
     }
+
+    // ── Non-Windows dotnet-host resolution (see GetDotNetCommand) ──────────────
+    // Exercised directly against the extracted pure function so both branches are
+    // covered regardless of which OS actually runs the test.
+
+    [Fact]
+    public void ResolveNonWindowsDotNetCommand_falls_back_to_bare_dotnet_when_DOTNET_ROOT_is_null()
+    {
+        var command = OutProcReqnrollConnector.ResolveNonWindowsDotNetCommand(null);
+
+        command.Should().Be("dotnet", "PATH resolution is the standard install on Linux/macOS");
+    }
+
+    [Fact]
+    public void ResolveNonWindowsDotNetCommand_falls_back_to_bare_dotnet_when_DOTNET_ROOT_is_empty()
+    {
+        var command = OutProcReqnrollConnector.ResolveNonWindowsDotNetCommand("");
+
+        command.Should().Be("dotnet", "PATH resolution is the standard install on Linux/macOS");
+    }
+
+    [Fact]
+    public void ResolveNonWindowsDotNetCommand_prefers_DOTNET_ROOT_when_set()
+    {
+        var dotNetRoot = Path.Combine(Path.GetTempPath(), "dotnet-root");
+
+        var command = OutProcReqnrollConnector.ResolveNonWindowsDotNetCommand(dotNetRoot);
+
+        command.Should().Be(Path.Combine(dotNetRoot, "dotnet"));
+    }
 }