main: Set up a decimal context that safely handles currency.

import2ledger/__main__.py

@@ -1,5 +1,6 @@
 import collections
 import contextlib
+import decimal
 import logging
 import sys
 
@@ -87,6 +88,22 @@ def setup_logger(logger, main_config, stream):
     handler.setFormatter(formatter)
     logger.addHandler(handler)
 
+def decimal_context(base=decimal.BasicContext):
+    context = base.copy()
+    context.rounding = decimal.ROUND_HALF_EVEN
+    context.traps = {
+        decimal.Clamped: True,
+        decimal.DivisionByZero: True,
+        decimal.FloatOperation: True,
+        decimal.Inexact: False,
+        decimal.InvalidOperation: True,
+        decimal.Overflow: True,
+        decimal.Rounded: False,
+        decimal.Subnormal: True,
+        decimal.Underflow: True,
+    }
+    return context
+
 def main(arglist=None, stdout=sys.stdout, stderr=sys.stderr):
     try:
         my_config = config.Configuration(arglist)
@@ -94,14 +111,15 @@ def main(arglist=None, stdout=sys.stdout, stderr=sys.stderr):
         my_config.error("{}: {!r}".format(error.strerror, error.user_input))
         return 3
     setup_logger(logger, my_config, stderr)
-    importer = FileImporter(my_config, stdout)
-    failures = 0
-    for input_path, error in importer.import_paths(my_config.args.input_paths):
-        if error is None:
-            logger.info("%s: imported", input_path)
-        else:
-            logger.warning("%s: failed to import: %s", input_path or error.path, error)
-            failures += 1
+    with decimal.localcontext(decimal_context()):
+        importer = FileImporter(my_config, stdout)
+        failures = 0
+        for input_path, error in importer.import_paths(my_config.args.input_paths):
+            if error is None:
+                logger.info("%s: imported", input_path)
+            else:
+                logger.warning("%s: failed to import: %s", input_path or error.path, error)
+                failures += 1
     if failures == 0:
         return 0
     else:

tests/__init__.py

@@ -1,6 +1,11 @@
+import decimal
 import pathlib
 import re
 
+from import2ledger import __main__ as i2lmain
+
+decimal.setcontext(i2lmain.decimal_context())
+
 DATA_DIR = pathlib.Path(__file__).with_name('data')
 
 def normalize_whitespace(s):