Fix truncating file handle (#38425)

Author: shunping

sdks/python/apache_beam/dataframe/io.py

@@ -515,7 +515,7 @@ def seekable(self):
 
   @property
   def closed(self):
-    return False
+    return getattr(self._underlying, 'closed', False)
 
   def __iter__(self):
     # For pandas is_file_like.
@@ -584,7 +584,18 @@ def _read(self, size=-1):
     return res
 
   def flush(self):
-    self._underlying.flush()
+    if not self.closed:
+      try:
+        self._underlying.flush()
+      except ValueError:
+        pass
+
+  def close(self):
+    if not self.closed and hasattr(self._underlying, 'close'):
+      try:
+        self._underlying.close()
+      except (OSError, ValueError):
+        pass
 
 
 class _ReadFromPandasDoFn(beam.DoFn, beam.RestrictionProvider):

sdks/python/apache_beam/dataframe/io_test.py

@@ -296,6 +296,51 @@ def test_truncating_filehandle_iter(self):
     self._run_truncating_file_handle_iter_test('aaa b cccccccccccccccccccc')
     self._run_truncating_file_handle_iter_test('aaa b ccccccccccccccccc ')
 
+  def test_truncating_filehandle_flush_on_closed_stream(self):
+    class ClosedFlushingStream(StringIO):
+      def flush(self):
+        if self.closed:
+          raise ValueError("I/O operation on closed file.")
+        super().flush()
+
+    s = 'a b c'
+    tracker = restriction_trackers.OffsetRestrictionTracker(
+        restriction_trackers.OffsetRange(0, len(s)))
+    underlying = ClosedFlushingStream(s)
+    handle = io._TruncatingFileHandle(
+        underlying, tracker, splitter=io._DelimSplitter(' ', 10))
+
+    # Verify that calling flush() when the underlying stream is closed
+    # succeeds without raising ValueError.
+    underlying.close()
+    handle.flush()
+    handle.close()
+
+  def test_truncating_filehandle_exception_suppression(self):
+    class FaultyStream(StringIO):
+      @property
+      def closed(self):
+        return False
+
+      def flush(self):
+        raise ValueError("Simulated flush error")
+
+      def close(self):
+        raise OSError("Simulated close error")
+
+    s = 'a b c'
+    tracker = restriction_trackers.OffsetRestrictionTracker(
+        restriction_trackers.OffsetRange(0, len(s)))
+    underlying = FaultyStream(s)
+    handle = io._TruncatingFileHandle(
+        underlying, tracker, splitter=io._DelimSplitter(' ', 10))
+
+    # Verify that ValueError raised during flush() is safely suppressed.
+    handle.flush()
+
+    # Verify that OSError raised during close() is safely suppressed.
+    handle.close()
+
   @parameterized.expand([
       ('defaults', {}),
       ('header', dict(header=1)),