Use absolute file name for stat (#1713)

Author: BCSharp

Src/IronPython.Modules/nt.cs

@@ -439,20 +439,20 @@ public static object fstat(CodeContext/*!*/ context, int fd) {
             PythonContext pythonContext = context.LanguageContext;
             pythonContext.FileManager.TryGetObjectFromId(pythonContext, fd, out object obj);
             if (obj is PythonIOModule.FileIO file) {
-                if (file.IsConsole) return new stat_result(8192);
+                if (file.IsConsole) return new stat_result(0x2000);
                 if (StatStream(file._readStream) is not null and var res) return res;
-                if (file.name is string strName) return lstat(strName, new Dictionary<string, object>(1));
             } else if (obj is Stream stream && StatStream(stream) is not null and var res) {
                 return res;
             }
             return LightExceptions.Throw(PythonOps.OSError(9, "Bad file descriptor"));
 
-            static stat_result? StatStream(Stream stream) {
-                if (stream is PipeStream) return new stat_result(4096);
+            static object? StatStream(Stream stream) {
+                if (stream is FileStream fs) return lstat(fs.Name, new Dictionary<string, object>(1));
+                if (stream is PipeStream) return new stat_result(0x1000);
                 if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows)) {
-                    if (ReferenceEquals(stream, Stream.Null)) return new stat_result(8192);
+                    if (ReferenceEquals(stream, Stream.Null)) return new stat_result(0x2000);
                 } else if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux) || RuntimeInformation.IsOSPlatform(OSPlatform.OSX)) {
-                    if (IsUnixStream(stream)) return new stat_result(4096);
+                    if (IsUnixStream(stream)) return new stat_result(0x1000);
                 }
                 return null;
             }

Tests/modules/io_related/test_fd.py

@@ -216,4 +216,17 @@ def test_pipe_fds(self):
         for i in range(1, 3):
             os.unlink(test_filename + str(i))
 
+    def test_stat_chdir(self):
+        test_filename = "tmp_%d.stat.test" % os.getpid()
+        fd = os.open(test_filename, os.O_CREAT | os.O_RDWR)
+        self.assertIsNotNone(os.fstat(fd))
+        cwd = os.getcwd()
+        os.chdir(os.sep)
+        try:
+            self.assertIsNotNone(os.fstat(fd))
+        finally:
+            os.chdir(cwd)
+        os.close(fd)
+        os.unlink(test_filename)
+
 run_test(__name__)