refactor(chart-engine): centralize chart metadata access helpers

clean_slides/chart_engine/builder.py

@@ -13,7 +13,7 @@
 from pptx.oxml.ns import qn
 from pptx.util import Emu, Inches, Pt
 
-from ..pptx_access import chart_series_names, shape_has_text_frame, slide_charts
+from ..pptx_access import chart_series_names, chart_xml_space, shape_has_text_frame, slide_charts
 from . import annotations as _annotations
 from . import payloads as _payloads
 from .colors import apply_color
@@ -162,7 +162,7 @@ def _chart_box(value: tuple[object, object, object, object]) -> ChartBox | None:
 
 
 def apply_chart_template_dlbls(
-    target_chart: Any,
+    target_chart: object,
     template_path: Path,
     slide_index: int = 0,
     chart_index: int = 0,
@@ -178,10 +178,13 @@ def apply_chart_template_dlbls(
         return
 
     template_chart = template_charts[chart_index]
+    template_chart_space = chart_xml_space(template_chart)
+    target_chart_space = chart_xml_space(target_chart)
+    if template_chart_space is None or target_chart_space is None:
+        return
 
-    template_chart_obj = cast(Any, template_chart)
-    template_series = get_chart_series(template_chart_obj._chartSpace)
-    target_series = get_chart_series(target_chart._chartSpace)
+    template_series = get_chart_series(template_chart_space)
+    target_series = get_chart_series(target_chart_space)
     if not template_series or not target_series:
         return
     if series_index < 0 or series_index >= len(template_series):

clean_slides/chart_engine/template_ops.py

@@ -8,11 +8,11 @@
 import zipfile
 from collections.abc import Sequence
 from pathlib import Path
-from typing import Any, NamedTuple, cast
+from typing import NamedTuple
 
 from pptx import Presentation
 
-from ..pptx_access import slide_charts
+from ..pptx_access import chart_part_name, slide_charts
 
 
 def read_pptx_part(path: Path, part_name: str) -> bytes:
@@ -69,8 +69,11 @@ def replace_chart_with_template(
         )
 
     template_chart = template_charts[template_chart_index]
-    template_chart_obj = cast(Any, template_chart)
-    template_chart_part = str(template_chart_obj.part.partname).lstrip("/")
+    template_chart_part_name = chart_part_name(template_chart)
+    if template_chart_part_name is None:
+        raise ValueError("Template chart is missing partname")
+
+    template_chart_part = template_chart_part_name.lstrip("/")
     template_chart_rels_part = f"ppt/charts/_rels/{Path(template_chart_part).name}.rels"
 
     template_chart_xml = read_pptx_part(template_path, template_chart_part)

clean_slides/pptx_access.py

@@ -168,6 +168,13 @@ def chart_xml_element(chart: object) -> object | None:
     return getattr(chart, "_element", None)
 
 
+def chart_part_name(chart: object) -> str | None:
+    """Return chart partname (e.g. '/ppt/charts/chart1.xml') when available."""
+    chart_part = getattr(chart, "part", None)
+    partname = getattr(chart_part, "partname", None)
+    return str(partname) if partname is not None else None
+
+
 class _AddChartCallable(Protocol):
     def __call__(
         self,

tests/test_pptx_access.py

@@ -4,6 +4,7 @@
 
 from clean_slides.pptx_access import (
     chart_first_plot,
+    chart_part_name,
     chart_plots,
     chart_series,
     chart_series_names,
@@ -61,10 +62,16 @@ class _Chart:
     series: list[object]
     _chartSpace: object | None = None
     _element: object | None = None
+    part: object | None = None
     plots: list[object] = field(default_factory=_object_list)
     has_legend: bool = True
 
 
+@dataclass
+class _ChartPart:
+    partname: str
+
+
 @dataclass
 class _TextFrame:
     text: str
@@ -229,7 +236,12 @@ def test_shape_and_text_frame_helpers_cover_text_placeholder_connector() -> None
     text_frame = _TextFrame(text="  Hello  ", paragraphs=[object()], _element={"tag": "txBody"})
     shape = _Shape(
         has_chart=True,
-        chart=_Chart(chart_type=57, series=[_Series(name="Revenue")], _chartSpace={"tag": "cs"}),
+        chart=_Chart(
+            chart_type=57,
+            series=[_Series(name="Revenue")],
+            _chartSpace={"tag": "cs"},
+            part=_ChartPart(partname="/ppt/charts/chart7.xml"),
+        ),
         has_text_frame=True,
         text_frame=text_frame,
         text="inline",
@@ -259,6 +271,7 @@ def test_shape_and_text_frame_helpers_cover_text_placeholder_connector() -> None
     assert shape_xml_element(shape) == {"tag": "shape"}
 
     assert chart_xml_space(chart) == {"tag": "cs"}
+    assert chart_part_name(chart) == "/ppt/charts/chart7.xml"
 
     paragraph = _Paragraph(_element={"tag": "p"})
     assert paragraph_xml_element(paragraph) == {"tag": "p"}