fix(table-patch): keep the saved height of a table split across pages

CHANGELOG.md

@@ -18,6 +18,11 @@
 
 ### 고침
 
+- 표 행·열·칸 구조 편집(객체 경로와 `apply_table_ops`)이 쪽을 넘어 나뉜 표의 저장 높이(`hp:sz`)를 그대로 둔다. 한/글은
+  그런 표에 첫 쪽 조각의 높이만 저장하므로(같은 행의 표가 놓인 자리에 따라 30463·17551·5865로 저장됨) 행 높이 증감을
+  더할 근거가 없다. 전에는 증감을 그대로 더해, 평가계획 채우기가 13행 표(행 28762, 저장 13222)에서 9행을 지우면
+  높이가 0이 됐다(#539 후속). 행 높이만큼 저장된 표는 전처럼 증감만큼 움직인다.
+
 - 줄 캐시(`write_line_caches`)가 머리에 정의되지 않은 글머리표·번호를 가리키는 문단 모양(예: 글머리표 idRef 0)의
   문단에는 캐시를 쓰지 않는다. 한/글은 정의가 없어도 글머리 자리를 잡아 첫 줄에 글자를 덜 넣는데, 전에는 글머리 없이
   나눈 줄을 써서 한/글이 그 줄을 눌러 담을 수 있었다.

src/hwpx/oxml/table_structure.py

@@ -157,13 +157,20 @@ def _rows_height(self) -> int | None:
     def _grow_height(self, before: int | None) -> None:
         """Move the table's saved height (``hp:sz``) by what its rows gained or lost in the edit, as
         Hancom saves the height of the rows it lays out: the rows left as they were keep the height Hancom
-        gave them. With rows the estimate does not follow, the height stays as it was."""
+        gave them. With rows the estimate does not follow, the height stays as it was.
+
+        A table saved shorter than its rows is one Hancom split across pages: it saves the height of the
+        part on the table's first page (tables of the same rows save different heights by where they start),
+        and the rows' gain or loss does not say how that part changes. Its height also stays as it was, rather
+        than moving by the whole delta, which can take it to nothing."""
 
         after = self._rows_height()
         size = self.element.find(f"{_HP}sz")
         if before is None or after is None or size is None or after == before:
             return
         height = int(size.get("height", 0) or 0)
+        if height < before:
+            return
         size.set("height", str(max(0, height + after - before)))
 
 

tests/test_table_structure_edits.py

@@ -376,3 +376,41 @@ def test_a_table_holding_a_table_keeps_it_through_an_edit() -> None:
     assert [table.cell(row, 0).tables[0].cell(0, 0).text for row in (0, 1)] == ["inner", "inner"]
     with HwpxDocument.open(document.to_bytes()) as reopened:
         assert reopened.tables[0].row_count == 3
+
+
+BLANK_3HAK = Path(__file__).parent / "fixtures" / "m105_evalplan" / "blank_form_3hak.hwpx"
+
+
+def _saved_heights(data: bytes) -> list[int]:
+    with zipfile.ZipFile(io.BytesIO(data)) as archive:
+        section = etree.fromstring(archive.read("Contents/section0.xml"))
+    return [int(table.find(HP + "sz").get("height")) for table in section.iter(HP + "tbl")]
+
+
+def test_a_table_hancom_split_across_pages_keeps_its_saved_height_through_row_edits() -> None:
+    # In this Hancom-saved evaluation plan, tables 19-21 have the same 15 rows and save 30463, 17551 and 5865:
+    # a table split across pages saves the height of its part on the first page, not its rows' height. Table 8
+    # (13 rows of 28762 saved as 13222) is one of them. Moving that height by the rows' delta took it to 0
+    # when the evaluation-plan fill deleted nine of its rows.
+    source = BLANK_3HAK.read_bytes()
+    saved = _saved_heights(source)
+    assert saved[19:22] == [30463, 17551, 5865]
+    op = {"op": "delete_row", "table_index": 8, "rows": list(range(4, 13))}
+
+    by_bytes = apply_table_ops(source, [op])
+    assert by_bytes.ok, by_bytes.skipped
+    assert _saved_heights(by_bytes.data)[8] == saved[8] == 13222
+
+    document = HwpxDocument.open(source)
+    document.tables.all[8].delete_rows(list(range(4, 13)))
+    assert _saved_heights(document.to_bytes())[8] == 13222
+
+
+def test_a_table_saved_as_tall_as_its_rows_still_moves_by_their_delta() -> None:
+    # Table 9 of the same form fits its page: it saves its rows' 25961, so a deleted row takes its height.
+    source = BLANK_3HAK.read_bytes()
+    assert _saved_heights(source)[9] == 25961
+
+    result = apply_table_ops(source, [{"op": "delete_row", "table_index": 9, "rows": [9]}])
+    assert result.ok, result.skipped
+    assert 0 < _saved_heights(result.data)[9] < 25961