update docstring, fix error msg

Author: fangchenli

pandas/io/common.py

@@ -1356,8 +1356,9 @@ def iterdir(
 
     Returns
     ------
-    pathlib.Path or pathlib.PurePosixPath
-        File paths within the directory.
+    list of str or Path, BaseBuffer
+        If `path` is a file-like object, returns it directly.
+        Otherwise, returns list of file paths in the directory.
 
     Raises
     ------

pandas/tests/io/parser/common/test_file_buffer_url.py

@@ -314,21 +314,21 @@ class InvalidBuffer:
         pass
 
     parser = all_parsers
-    msg = "Invalid file path or buffer object type"
+    msg = "Expected file path name or file-like object"
 
-    with pytest.raises(ValueError, match=msg):
+    with pytest.raises(TypeError, match=msg):
         parser.read_csv(InvalidBuffer())
 
 
 def test_invalid_file_buffer_mock(all_parsers):
     # see gh-15337
     parser = all_parsers
-    msg = "Invalid file path or buffer object type"
+    msg = "Expected file path name or file-like object"
 
     class Foo:
         pass
 
-    with pytest.raises(ValueError, match=msg):
+    with pytest.raises(TypeError, match=msg):
         parser.read_csv(Foo())