reports: BaseODS.currency_cell() sets default style.

It'll be rare we don't want this.

conservancy_beancount/reports/core.py

@@ -922,6 +922,8 @@ class BaseODS(BaseSpreadsheet[RT, ST], metaclass=abc.ABCMeta):
             return self.multiline_cell(lines, **attrs)
 
     def currency_cell(self, amount: data.Amount, **attrs: Any) -> odf.table.TableCell:
+        if 'stylename' not in attrs:
+            attrs['stylename'] = self.currency_style(amount.currency)
         number, currency = amount
         cell = odf.table.TableCell(valuetype='currency', value=number, **attrs)
         cell.addElement(odf.text.P(text=babel.numbers.format_currency(

tests/test_reports_spreadsheet.py

@@ -470,6 +470,19 @@ def test_ods_writer_currency_cell(ods_writer, cell_source, style_name):
     )
     assert get_text(cell) == expected
 
+@pytest.mark.parametrize('currency', [
+    'EUR',
+    'CHF',
+    'GBP',
+])
+def test_ods_writer_currency_cell_default_style(ods_writer, currency):
+    amount = testutil.Amount(1000, currency)
+    expected_stylename = ods_writer.currency_style(currency).getAttribute('name')
+    cell = ods_writer.currency_cell(amount)
+    assert cell.getAttribute('valuetype') == 'currency'
+    assert cell.getAttribute('value') == '1000'
+    assert cell.getAttribute('stylename') == expected_stylename
+
 @pytest.mark.parametrize('date,style_name', testutil.combine_values(
     [datetime.date(1980, 2, 5), datetime.date(2030, 10, 30)],
     XML_NAMES_LIST,