template: Improve error detection and reporting in amount expressions.

import2ledger/template.py

@@ -52,7 +52,15 @@ class TokenTransformer:
 class AmountTokenTransformer(TokenTransformer):
     SUPPORTED_OPS = frozenset('+-*/()')
 
-    transform_NAME = TokenTransformer._noop_transformer
+    def __iter__(self):
+        tokens = super().__iter__()
+        for token in tokens:
+            yield token
+            if token[0] == tokenize.NAME:
+                break
+        else:
+            raise ValueError("no amount in expression")
+        yield from tokens
 
     def transform_NUMBER(self, ttype, tvalue):
         yield (tokenize.NAME, 'Decimal')
@@ -66,6 +74,7 @@ class AmountTokenTransformer(TokenTransformer):
                 name_type, name_value, _, _, _ = next(self.in_tokens)
                 close_type, close_value, _, _, _ = next(self.in_tokens)
                 if (name_type != tokenize.NAME
+                    or name_value != name_value.lower()
                     or close_type != tokenize.OP
                     or close_value != '}'):
                     raise ValueError()
@@ -91,9 +100,11 @@ class AccountSplitter:
     def add(self, account, amount_expr):
         try:
             clean_expr = AmountTokenTransformer.from_str(amount_expr).transform()
-        except ValueError as error:
+            compiled_expr = compile(clean_expr, self.template_name, 'eval')
+        except (SyntaxError, tokenize.TokenError, ValueError) as error:
             raise errors.UserInputConfigurationError(error.args[0], amount_expr)
-        self.splits[account] = compile(clean_expr, self.template_name, 'eval')
+        else:
+            self.splits[account] = compiled_expr
 
     def _currency_decimal(self, amount, currency):
         return decimal.Decimal(babel.numbers.format_currency(amount, currency, '###0.###'))

tests/test_templates.py

@@ -4,7 +4,7 @@ import decimal
 import pathlib
 
 import pytest
-from import2ledger import template
+from import2ledger import errors, template
 
 from . import DATA_DIR, normalize_whitespace
 
@@ -87,3 +87,25 @@ def test_multivalue():
         "  Income:RBI  -15.00 USD",
         "  Income:Donations  -135.00 USD",
     ]
+
+@pytest.mark.parametrize('amount_expr', [
+    '',
+    'name',
+    '-',
+    '()',
+    '+()',
+    '{}',
+    '{{}}',
+    '{()}',
+    '{name',
+    'name}',
+    '{42}',
+    '(5).real',
+    '{amount.real}',
+    '{amount.is_nan()}',
+    '{Decimal}',
+    '{FOO}',
+])
+def test_bad_amount_expression(amount_expr):
+    with pytest.raises(errors.UserInputError):
+        template.Template(" Income  " + amount_expr)