refactor: expect writer to be closed when creating manifest files

pyiceberg/manifest.py

@@ -806,7 +806,7 @@ def __exit__(
         traceback: Optional[TracebackType],
     ) -> None:
         self._close_current_writer()
-        self.closed = True
+        self._closed = True
 
     def _get_current_writer(self) -> ManifestWriter:
         if self._should_roll_to_new_file():
@@ -833,8 +833,8 @@ def _close_current_writer(self):
             self._current_file_rows = 0
 
     def to_manifest_files(self) -> list[ManifestFile]:
-        self._close_current_writer()
-        self._closed = True
+        if not self._closed:
+            raise RuntimeError("Cannot create manifest files from unclosed writer")
         return self._manifest_files
 
     def add_entry(self, entry: ManifestEntry) -> RollingManifestWriter:

tests/utils/test_manifest.py

@@ -539,11 +539,12 @@ def supplier() -> Generator[ManifestWriter, None, None]:
         ) as writer:
             for entry in manifest_entries:
                 writer.add_entry(entry)
-            manifest_files = writer.to_manifest_files()
-            assert len(manifest_files) == expected_number_of_files
-            with pytest.raises(RuntimeError):
-                # It is already closed
-                writer.add_entry(manifest_entries[0])
+
+        manifest_files = writer.to_manifest_files()
+        assert len(manifest_files) == expected_number_of_files
+        with pytest.raises(RuntimeError):
+            # It is already closed
+            writer.add_entry(manifest_entries[0])
 
 
 @pytest.mark.parametrize("format_version", [1, 2])
@@ -613,3 +614,5 @@ def test_write_manifest_list(
         assert entry.file_sequence_number == 0 if format_version == 1 else 3
         assert entry.snapshot_id == 8744736658442914487
         assert entry.status == ManifestEntryStatus.ADDED
+
+