Add dotnetcli.host.json for slnf template and normalize path separators

Co-authored-by: baronfel <[email protected]>

Author: Copilot

src/Cli/dotnet/Commands/Solution/Add/SolutionAddCommand.cs

@@ -248,7 +248,7 @@ private async Task AddProjectsToSolutionFilterAsync(IEnumerable<string> projectP
         // Load the parent solution to validate projects exist in it
         SolutionModel parentSolution = SlnFileFactory.CreateFromFileOrDirectory(parentSolutionPath);
 
-        // Get existing projects in the filter
+        // Get existing projects in the filter (already normalized to OS separator by CreateFromFilteredSolutionFile)
         var existingProjects = filteredSolution.SolutionProjects.Select(p => p.FilePath).ToHashSet();
 
         // Get solution-relative paths for new projects
@@ -258,6 +258,9 @@ private async Task AddProjectsToSolutionFilterAsync(IEnumerable<string> projectP
         {
             string parentSolutionRelativePath = Path.GetRelativePath(parentSolutionDirectory, projectPath);
 
+            // Normalize to OS separator for consistent comparison
+            parentSolutionRelativePath = parentSolutionRelativePath.Replace('\\', Path.DirectorySeparatorChar).Replace('/', Path.DirectorySeparatorChar);
+
             // Check if project exists in parent solution
             var projectInParent = parentSolution.FindProject(parentSolutionRelativePath);
             if (projectInParent is null)

src/Cli/dotnet/SlnFileFactory.cs

@@ -91,6 +91,8 @@ public static SolutionModel CreateFromFilteredSolutionFile(string filteredSoluti
         {
             JsonElement root = JsonDocument.Parse(File.ReadAllText(filteredSolutionPath)).RootElement;
             originalSolutionPath = Uri.UnescapeDataString(root.GetProperty("solution").GetProperty("path").GetString());
+            // Normalize path separators to OS-specific for cross-platform compatibility
+            originalSolutionPath = originalSolutionPath.Replace('\\', Path.DirectorySeparatorChar).Replace('/', Path.DirectorySeparatorChar);
             filteredSolutionProjectPaths = [.. root.GetProperty("solution").GetProperty("projects").EnumerateArray().Select(p => p.GetString())];
             originalSolutionPathAbsolute = Path.GetFullPath(originalSolutionPath, Path.GetDirectoryName(filteredSolutionPath));
         }

template_feed/Microsoft.DotNet.Common.ItemTemplates/content/SolutionFilter/.template.config/dotnetcli.host.json

@@ -0,0 +1,9 @@
+{
+  "$schema": "http://json.schemastore.org/dotnetcli.host",
+  "symbolInfo": {
+    "ParentSolution": {
+      "longName": "parent-solution",
+      "shortName": "s"
+    }
+  }
+}