Fix(split_income): Convert positions to weight before subtracting tax…

…es (#8)

Previously, the code assumed that income and taxes used the same
currency. If the postings had an additional associated cost or price,
this was not considered. Now, to obtain the correct amount, the
beancount.core.convert.get_weight function is used. It provides the
amount that will need to be balanced from a posting of a transaction.

Appropriate tests are included.

Fixes #7

fava_plugins/split_income.py

@@ -54,6 +54,7 @@
 import copy
 import re
 
+from beancount.core import convert
 from beancount.core import data
 from beancount.core import getters
 from beancount.core.inventory import Inventory
@@ -112,14 +113,15 @@ def split_income(entries, options_map, config_str):
         income = collections.defaultdict(Inventory)
         taxes = collections.defaultdict(Decimal)
         for posting in list(entry.postings):
+            weight = convert.get_weight(posting)
             if posting.account.startswith(config["income"]):
                 new_entry.postings.append(posting)
                 entry.postings.remove(posting)
-                income[posting.account].add_amount(posting.units)
+                income[posting.account].add_amount(weight)
             elif re.match(config["taxes"], posting.account):
                 new_entry.postings.append(posting)
                 entry.postings.remove(posting)
-                taxes[posting.units.currency] += posting.units.number
+                taxes[weight.currency] += weight.number
 
         for account, inv in income.items():
             net_account = account.replace(

tests/test_split_income.py

@@ -99,3 +99,77 @@ def test_split_income_config(load_doc):
 
     assert len(entries) == 9
     assert len([e for e in entries if isinstance(e, data.Open)]) == 7
+
+
+def test_split_income_mixed_currency_income(load_doc):
+    """
+    plugin "fava_plugins.split_income" ""
+    plugin "beancount.plugins.auto_accounts"
+
+    2025-01-01 * "Employer" "Income"
+        Income:Work                       -10 USD @@ 9 EUR
+        Expenses:Taxes                      1 EUR
+        Assets:Account                      8 EUR
+    """
+
+    entries, errors, __ = load_doc
+
+    entries_after, _, __ = load_string(
+        """
+    2025-01-01 * "Employer" "Income"
+        Assets:Account                      8 EUR
+        Income:Net:Work                    -8 EUR
+
+    2025-01-01 * "Employer" "Income" #pretax
+        Income:Work                       -10 USD @ 0.9 EUR
+        Expenses:Taxes                     1 EUR
+        Income:Net:Work                    8 EUR
+    """,
+        dedent=True,
+    )
+
+    assert not errors
+    assert "pretax" in entries[5].tags
+
+    _compare_postings(entries[5], entries_after[1])
+    _compare_postings(entries[4], entries_after[0])
+
+    assert len(entries) == 6
+    assert len([e for e in entries if isinstance(e, data.Open)]) == 4
+
+
+def test_split_income_mixed_currency_others(load_doc):
+    """
+    plugin "fava_plugins.split_income" ""
+    plugin "beancount.plugins.auto_accounts"
+
+    2025-01-01 * "Employer" "Income"
+        Income:Work                       -11 USD
+        Expenses:Taxes                      1 EUR @ 1.1 USD
+        Assets:Account                      9 EUR @ 1.1 USD
+    """
+
+    entries, errors, __ = load_doc
+
+    entries_after, _, __ = load_string(
+        """
+    2025-01-01 * "Employer" "Income"
+        Assets:Account                      9 EUR @ 1.1 USD
+        Income:Net:Work                  -9.9 USD
+
+    2025-01-01 * "Employer" "Income" #pretax
+        Income:Work                       -11 USD
+        Expenses:Taxes                     1 EUR @ 1.1 USD
+        Income:Net:Work                    9.9 USD
+    """,
+        dedent=True,
+    )
+
+    assert not errors
+    assert "pretax" in entries[5].tags
+
+    _compare_postings(entries[5], entries_after[1])
+    _compare_postings(entries[4], entries_after[0])
+
+    assert len(entries) == 6
+    assert len([e for e in entries if isinstance(e, data.Open)]) == 4