meta_entity: Set metadata when entity comes from payee. RT#12525

This makes it easier to write bean-queries, since you don't have to check
two places for the "real" entity.

conservancy_beancount/plugin/meta_entity.py

@@ -72,6 +72,8 @@ class MetaEntity(core.TransactionHook):
         txn_entity, txn_entity_ok = self._check_entity(txn.meta, txn.payee)
         if txn_entity_ok is False:
             yield errormod.InvalidMetadataError(txn, self.METADATA_KEY, txn_entity)
+        if txn_entity is txn.payee:
+            txn.meta[self.METADATA_KEY] = txn.payee
         for post in data.Posting.from_txn(txn):
             if not post.account.is_under(
                     'Assets:Receivable',

tests/test_meta_entity.py

@@ -118,11 +118,13 @@ def test_invalid_values_on_postings(hook, src_value):
 
 @pytest.mark.parametrize('src_value', VALID_VALUES)
 def test_valid_values_on_transactions(hook, src_value):
-    txn = testutil.Transaction(**{TEST_KEY: src_value}, postings=[
+    txn = testutil.Transaction(payee='Payee', **{TEST_KEY: src_value}, postings=[
         ('Assets:Cash', -25),
         ('Expenses:General', 25),
     ])
     assert not any(hook.run(txn))
+    # Make sure payee doesn't overwrite metadata. See payee test below.
+    assert txn.meta[TEST_KEY] == src_value
 
 @pytest.mark.parametrize('src_value', ANONYMOUS_VALUES)
 def test_anonymous_values_on_transactions(hook, src_value):
@@ -151,6 +153,9 @@ def test_valid_values_on_payee(hook, src_value):
         ('Expenses:General', 25),
     ])
     assert not any(hook.run(txn))
+    # In this case, we want the hook to set metadata to make it easier to
+    # write bean-queries.
+    assert txn.meta[TEST_KEY] == src_value
 
 @pytest.mark.parametrize('src_value', ANONYMOUS_VALUES)
 def test_anonymous_values_on_payee(hook, src_value):