data: Start iter_postings function.

conservancy_beancount/data.py

@@ -68,3 +68,10 @@ class PostingMeta(collections.abc.MutableMapping):
             raise KeyError(key)
         else:
             del self.post.meta[key]
+
+
+def iter_postings(txn: Transaction) -> Iterator[Posting]:
+    for index, source in enumerate(txn.postings):
+        yield source._replace(
+            meta=PostingMeta(txn, index, source),
+        )

tests/test_data_iter_postings.py

@@ -0,0 +1,41 @@
+"""Test data.iter_postings function"""
+# Copyright © 2020  Brett Smith
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+import pytest
+
+from . import testutil
+
+from beancount.core import data as bc_data
+from conservancy_beancount import data
+
+@pytest.fixture
+def simple_txn(index=None, key=None):
+    return testutil.Transaction(note='txn note', postings=[
+        ('Assets:Cash', 5),
+        ('Income:Donations', -5, {'note': 'donation love', 'extra': 'Extra'}),
+    ])
+
+def test_iter_postings(simple_txn):
+    for source, post in zip(simple_txn.postings, data.iter_postings(simple_txn)):
+        assert all(source[x] == post[x] for x in range(len(source) - 1))
+        assert post.meta['note']  # Only works with PostingMeta
+
+def test_editing_metadata_edits_source(simple_txn):
+    for index, post in enumerate(data.iter_postings(simple_txn)):
+        post.meta['edited'] = str(index)
+    for index, post in enumerate(simple_txn.postings):
+        assert post.meta['edited'] == str(index)
+        assert not isinstance(post.meta, data.PostingMeta)