python config access: fix style and KeyError bug

This fixes some minor style/pep8 things and adds tests for the new
config support.  Also fixes a bug where KeyError was never raised
on a missing key.

bindings/python-cffi/notmuch2/_config.py

@@ -4,9 +4,12 @@ import notmuch2._base as base
 import notmuch2._capi as capi
 import notmuch2._errors as errors
 
+
 __all__ = ['ConfigMapping']
 
+
 class ConfigIter(base.NotmuchIter):
+
     def __init__(self, parent, iter_p):
         super().__init__(
             parent, iter_p,
@@ -19,6 +22,7 @@ class ConfigIter(base.NotmuchIter):
         item = super().__next__()
         return base.BinString.from_cffi(item)
 
+
 class ConfigMapping(base.NotmuchObject, collections.abc.MutableMapping):
     """The config key/value pairs stored in the database.
 
@@ -50,11 +54,10 @@ class ConfigMapping(base.NotmuchObject, collections.abc.MutableMapping):
         ret = capi.lib.notmuch_database_get_config(self._ptr(), key, val_pp)
         if ret != capi.lib.NOTMUCH_STATUS_SUCCESS:
             raise errors.NotmuchError(ret)
-        if val_pp[0] == "":
-            capi.lib.free(val_pp[0])
-            raise KeyError
         val = base.BinString.from_cffi(val_pp[0])
         capi.lib.free(val_pp[0])
+        if val == '':
+            raise KeyError
         return val
 
     def __setitem__(self, key, val):

bindings/python-cffi/tests/test_config.py

@@ -0,0 +1,56 @@
+import collections.abc
+
+import pytest
+
+import notmuch2._database as dbmod
+
+import notmuch2._config as config
+
+
+class TestIter:
+
+    @pytest.fixture
+    def db(self, maildir):
+        with dbmod.Database.create(maildir.path) as db:
+            yield db
+
+    def test_type(self, db):
+        assert isinstance(db.config, collections.abc.MutableMapping)
+        assert isinstance(db.config, config.ConfigMapping)
+
+    def test_alive(self, db):
+        assert db.config.alive
+
+    def test_set_get(self, maildir):
+        # Ensure get-set works from different db objects
+        with dbmod.Database.create(maildir.path) as db0:
+            db0.config['spam'] = 'ham'
+        with dbmod.Database(maildir.path) as db1:
+            assert db1.config['spam'] == 'ham'
+
+    def test_get_keyerror(self, db):
+        with pytest.raises(KeyError):
+            val = db.config['not-a-key']
+            print(repr(val))
+
+    def test_iter(self, db):
+        assert list(db.config) == []
+        db.config['spam'] = 'ham'
+        db.config['eggs'] = 'bacon'
+        assert set(db.config) == {'spam', 'eggs'}
+        assert set(db.config.keys()) == {'spam', 'eggs'}
+        assert set(db.config.values()) == {'ham', 'bacon'}
+        assert set(db.config.items()) == {('spam', 'ham'), ('eggs', 'bacon')}
+
+    def test_len(self, db):
+        assert len(db.config) == 0
+        db.config['spam'] = 'ham'
+        assert len(db.config) == 1
+        db.config['eggs'] = 'bacon'
+        assert len(db.config) == 2
+
+    def test_del(self, db):
+        db.config['spam'] = 'ham'
+        assert db.config.get('spam') == 'ham'
+        del db.config['spam']
+        assert db.config.get('spam') is None