Added support for assert, check and expr directives

These can occur in many places:

  ; Within an automated transaction, the assert is evaluated every time
  ; a posting is matched, with the expression context set to the
  ; matching posting.
  = /Food/
    assert account("Expenses:Food").total >= $100

  2010-06-12 Sample
    Expenses:Food                $100
    Assets:Checking

  ; At file scope, the expression is evaluated with "global" scope.
  assert account("Expenses:Food").total == $100

  ; At the top of a transction, the assertion's scope is the
  ; transaction.  After a posting, the scope is that posting.  Note
  ; however that account totals are only adjusted after successful
  ; parsing of a transaction, which means that all the assertions below
  ; are true, even though it appears as though the middle posting should
  ; affect the total immediately (which is not the case).
  2010-06-12 Sample 2
    assert account("Expenses:Food").total == $100
    Expenses:Food                $50
    assert account("Expenses:Food").total == $100
    Assets:Checking
    assert account("Expenses:Food").total == $100

1 files changed, 15 insertions, 0 deletions

diff --git a/src/xact.cc b/src/xact.cc
index eeb487d9..0bf1fc2c 100644
--- a/src/xact.cc
+++ b/src/xact.cc
@@ -691,6 +691,21 @@ void auto_xact_t::extend_xact(xact_base_t&                xact,
                                      current_year);
         }
       }
+      if (check_exprs) {
+        foreach (check_expr_pair& pair, *check_exprs) {
+          if (pair.second == auto_xact_t::EXPR_GENERAL) {
+            pair.first.calc(bound_scope);
+          }
+          else if (! pair.first.calc(bound_scope).to_boolean()) {
+            if (pair.second == auto_xact_t::EXPR_ASSERTION) {
+              throw_(parse_error,
+                     _("Transaction assertion failed: %1" << pair.first));
+            } else {
+              warning_(_("Transaction check failed: %1" << pair.first));
+            }
+          }
+        }
+      }
 
       foreach (post_t * post, posts) {
         amount_t post_amount;