ledger_entry: Only try to balance entry amounts when necessary.

This gives template authors the ability to write entries that
balance something other than the "main" amount.

import2ledger/hooks/ledger_entry.py

@@ -190,8 +190,9 @@ class AccountSplitter:
                 "{}: {}".format(type(error).__name__, error),
                 "template {!r}".format(self.template_name)
             ) from error
-        self._balance_amounts(amounts, template_vars['amount'])
-        self._balance_amounts(amounts, -template_vars['amount'])
+        if sum(amt for _, amt in amounts) != 0:
+            self._balance_amounts(amounts, template_vars['amount'])
+            self._balance_amounts(amounts, -template_vars['amount'])
         return amounts
 
     def _iter_splits(self, template_vars):

setup.py

@@ -30,7 +30,7 @@ REQUIREMENTS['tests_require'] = [
 setup(
     name='import2ledger',
     description="Import different sources of financial data to Ledger",
-    version='0.9.1',
+    version='0.9.2',
     author='Brett Smith',
     author_email='brettcsmith@brettcsmith.org',
     license='GNU AGPLv3+',

tests/data/templates.ini

@@ -60,6 +60,11 @@ template =
  Income:Sales  -3 if 'x' not in {false} else -{amount}
  Assets:Cash   {amount}
 
+[SelfBalanced]
+template =
+ Income:Sales  -5
+ Assets:Cash    5
+
 [NondecimalWord]
 template =
  Income:Sales  -5

tests/test_hook_ledger_entry.py

@@ -214,6 +214,17 @@ def test_string_conditionals():
         "  Assets:Cash  6.00 USD",
     ]
 
+def test_self_balanced():
+    # The amount needs to be different than what's in the template.
+    render_vars = template_vars('NN', '0')
+    lines = render_lines(render_vars, 'SelfBalanced')
+    assert lines == [
+        "",
+        "2015/03/14 NN",
+        "  Income:Sales  -5.00 USD",
+        "  Assets:Cash  5.00 USD",
+    ]
+
 @pytest.mark.parametrize('amount_expr', [
     '',
     'name',