realpath in c#

src/Resolvers/Microsoft.DotNet.NativeWrapper/EnvironmentProvider.cs

@@ -59,7 +59,7 @@ private IEnumerable<string> SearchPaths
             }
 
             string? dotnetExe;
-#if NETCOREAPP
+#if NET
             // The dotnet executable is loading only the .NET version of this code so there is no point checking
             // the current process path on .NET Framework. We are expected to find dotnet on PATH.
             dotnetExe = _getCurrentProcessPath();
@@ -70,12 +70,41 @@ private IEnumerable<string> SearchPaths
             {
                 string? dotnetExeFromPath = GetCommandPath(Constants.DotNet);
 
-                if (dotnetExeFromPath != null && !Interop.RunningOnWindows)
+#if NET
+                if (dotnetExeFromPath != null && !OperatingSystem.IsWindows())
                 {
                     // e.g. on Linux the 'dotnet' command from PATH is a symlink so we need to
                     // resolve it to get the actual path to the binary
-                    dotnetExeFromPath = Interop.Unix.realpath(dotnetExeFromPath) ?? dotnetExeFromPath;
+                    dotnetExeFromPath = GetRealPath(dotnetExeFromPath);
+
+                    static string GetRealPath(string path)
+                    {
+                        FileInfo fileInfo = new FileInfo(path);
+                        if (fileInfo.LinkTarget != null)
+                        {
+                            var resolved = fileInfo.ResolveLinkTarget(true);
+                            return resolved?.Exists is true ? resolved.FullName : path;
+                        }
+
+                        string invariantPart = string.Empty;
+                        DirectoryInfo? parentDirectory = fileInfo.Directory;
+                        while (parentDirectory is not null)
+                        {
+                            invariantPart = path[parentDirectory.FullName.Length..];
+                            if (parentDirectory.LinkTarget != null)
+                            {
+                                var resolved = parentDirectory.ResolveLinkTarget(true);
+                                if (resolved?.Exists is true)
+                                    return Path.Join(resolved.FullName, invariantPart);
+                            }
+
+                            parentDirectory = parentDirectory.Parent;
+                        }
+
+                        return path;
+                    }
                 }
+#endif
 
                 if (!string.IsNullOrWhiteSpace(dotnetExeFromPath))
                 {
@@ -86,7 +115,7 @@ private IEnumerable<string> SearchPaths
                     log?.Invoke($"GetDotnetExeDirectory: dotnet command path not found.  Using current process");
                     log?.Invoke($"GetDotnetExeDirectory: Path variable: {_getEnvironmentVariable(Constants.PATH)}");
 
-#if !NETCOREAPP
+#if !NET
                     // If we failed to find dotnet on PATH, we revert to the old behavior of returning the current process
                     // path. This is really an error state but we're keeping the contract of always returning a non-empty
                     // path for backward compatibility.
@@ -123,7 +152,7 @@ private IEnumerable<string> SearchPaths
         private static string? GetCurrentProcessPath()
         {
             string? currentProcessPath;
-#if NET6_0_OR_GREATER
+#if NET
             currentProcessPath = Environment.ProcessPath;
 #else
             currentProcessPath = Process.GetCurrentProcess().MainModule.FileName;

src/Resolvers/Microsoft.DotNet.NativeWrapper/Interop.cs

@@ -28,7 +28,7 @@ static Interop()
         }
 
         // MSBuild SDK resolvers are required to be AnyCPU, but we have a native dependency and .NETFramework does not
-        // have a built-in facility for dynamically loading user native dlls for the appropriate platform. We therefore 
+        // have a built-in facility for dynamically loading user native dlls for the appropriate platform. We therefore
         // preload the version with the correct architecture (from a corresponding sub-folder relative to us) on static
         // construction so that subsequent P/Invokes can find it.
         private static void PreloadWindowsLibrary(string dllFileName)
@@ -179,20 +179,6 @@ internal delegate void hostfxr_get_available_sdks_result_fn(
             internal static extern int hostfxr_get_available_sdks(
                 string? exe_dir,
                 hostfxr_get_available_sdks_result_fn result);
-
-            [DllImport("libc", CharSet = UTF8, ExactSpelling = true, CallingConvention = CallingConvention.Cdecl)]
-            private static extern IntPtr realpath(string path, IntPtr buffer);
-
-            [DllImport("libc", ExactSpelling = true, CallingConvention = CallingConvention.Cdecl)]
-            private static extern void free(IntPtr ptr);
-
-            public static string? realpath(string path)
-            {
-                var ptr = realpath(path, IntPtr.Zero);
-                var result = PtrToStringUTF8(ptr);
-                free(ptr);
-                return result;
-            }
         }
     }
 }