data: Add Account.keeps_balance() method.

conservancy_beancount/data.py

@@ -285,6 +285,12 @@ class Account(str):
                 return prefix
         return None
 
+    def keeps_balance(self) -> bool:
+        return self.is_under(
+            self._options_map['name_assets'],
+            self._options_map['name_liabilities'],
+        ) is not None
+
     def _find_part_slice(self, index: int) -> slice:
         if index < 0:
             raise ValueError(f"bad part index {index!r}")

tests/test_data_account.py

@@ -160,6 +160,30 @@ def test_is_credit_card(acct_name, expected):
 def test_is_opening_equity(acct_name, expected):
     assert data.Account(acct_name).is_opening_equity() == expected
 
+@pytest.mark.parametrize('acct_name', [
+    'Assets:Cash',
+    'Assets:Prepaid:Expenses',
+    'Assets:Receivable:Accounts',
+    'Expenses:Other',
+    'Equity:Funds:Restricted',
+    'Equity:OpeningBalance',
+    'Income:Other',
+    'Liabilities:CreditCard',
+    'Liabilities:Payable:Accounts',
+    'Liabilities:UnearnedIncome:Donations',
+])
+def test_keeps_balance(acct_name):
+    expected = acct_name.startswith(('Assets:', 'Liabilities:'))
+    assert data.Account(acct_name).keeps_balance() == expected
+
+def test_keeps_balance_uses_options(clean_account_meta):
+    config = bc_options.OPTIONS_DEFAULTS.copy()
+    config['name_liabilities'] = 'Debts'
+    data.Account.load_options_map(config)
+    assert not data.Account('Liabilities:CreditCard').keeps_balance()
+    assert data.Account('Debts:Payable').keeps_balance()
+    assert data.Account('Assets:Receivable').keeps_balance()
+
 @pytest.mark.parametrize('acct_name', [
     'Assets:Cash',
     'Assets:Receivable:Accounts',