fix segfaults in Python cFFI API and add tests

Several iterators in the Python cFFI API destroyed the objects they iterated
over too early (when the iterator was exhausted), causing subsequent segfaults
in common cases like creating a list from the iterator. This patch fixes the
segfaults and add tests to ensure that they don't happen again.

bindings/python-cffi/notmuch2/_base.py

@@ -167,7 +167,7 @@ class NotmuchIter(NotmuchObject, collections.abc.Iterator):
     It is tempting to use a generator function instead, but this would
     not correctly respect the :class:`NotmuchObject` memory handling
     protocol and in some unsuspecting cornercases cause memory
-    trouble.  You probably want to sublcass this in order to wrap the
+    trouble.  You probably want to subclass this in order to wrap the
     value returned by :meth:`__next__`.
 
     :param parent: The parent object.
@@ -223,7 +223,6 @@ class NotmuchIter(NotmuchObject, collections.abc.Iterator):
 
     def __next__(self):
         if not self._fn_valid(self._iter_p):
-            self._destroy()
             raise StopIteration()
         obj_p = self._fn_get(self._iter_p)
         self._fn_next(self._iter_p)

bindings/python-cffi/notmuch2/_message.py

@@ -610,7 +610,7 @@ class PropertiesMap(base.NotmuchObject, collections.abc.MutableMapping):
     def getall(self, prefix='', *, exact=False):
         """Return an iterator yielding all properties for a given key prefix.
 
-        The returned iterator yields all peroperties which start with
+        The returned iterator yields all properties which start with
         a given key prefix as ``(key, value)`` namedtuples.  If called
         with ``exact=True`` then only properties which exactly match
         the prefix are returned, those a key longer than the prefix
@@ -655,7 +655,6 @@ class PropertiesIter(base.NotmuchIter):
 
     def __next__(self):
         if not self._fn_valid(self._iter_p):
-            self._destroy()
             raise StopIteration
         key = capi.lib.notmuch_message_properties_key(self._iter_p)
         value = capi.lib.notmuch_message_properties_value(self._iter_p)

bindings/python-cffi/notmuch2/_query.py

@@ -52,7 +52,7 @@ class Query(base.NotmuchObject):
         This executes the query and returns an iterator over the
         :class:`Message` objects found.
         """
-        msgs_pp = capi.ffi.new('notmuch_messages_t**')
+        msgs_pp = capi.ffi.new('notmuch_messages_t **')
         ret = capi.lib.notmuch_query_search_messages(self._query_p, msgs_pp)
         if ret != capi.lib.NOTMUCH_STATUS_SUCCESS:
             raise errors.NotmuchError(ret)

bindings/python-cffi/tests/test_database.py

@@ -303,6 +303,18 @@ class TestQuery:
         msgs = db.messages('*')
         assert isinstance(msgs, collections.abc.Iterator)
 
+    def test_messages_iterator(self, db):
+        for msg in db.messages('*'):
+            assert isinstance(msg, notmuch2.Message)
+            assert isinstance(msg.messageid, str)
+
+    def test_messages_iterator_list(self, db):
+        msgs = list(db.messages('*'))
+        assert len(msgs) == 3
+        for msg in msgs:
+            assert isinstance(msg, notmuch2.Message)
+            assert isinstance(msg.messageid, str)
+
     def test_message_no_results(self, db):
         msgs = db.messages('not_a_matching_query')
         with pytest.raises(StopIteration):
@@ -320,6 +332,25 @@ class TestQuery:
         threads = db.threads('*')
         assert isinstance(threads, collections.abc.Iterator)
 
+    def test_threads_iterator(self, db):
+        for t in db.threads('*'):
+            assert isinstance(t, notmuch2.Thread)
+            assert isinstance(t.threadid, str)
+            for msg in t:
+                assert isinstance(msg, notmuch2.Message)
+                assert isinstance(msg.messageid, str)
+
+    def test_threads_iterator_list(self, db):
+        threads = list(db.threads('*'))
+        assert len(threads) == 2
+        for t in threads:
+            assert isinstance(t, notmuch2.Thread)
+            assert isinstance(t.threadid, str)
+            msgs = list(t)
+            for msg in msgs:
+                assert isinstance(msg, notmuch2.Message)
+                assert isinstance(msg.messageid, str)
+
     def test_threads_no_match(self, db):
         threads = db.threads('not_a_matching_query')
         with pytest.raises(StopIteration):

bindings/python-cffi/tests/test_message.py

@@ -218,6 +218,20 @@ class TestProperties:
         props.add('foo', 'a')
         assert set(props.getall('foo')) == {('foo', 'a')}
 
+    def test_getall_iter(self, props):
+        props.add('foo', 'a')
+        props.add('foobar', 'b')
+        for prop in props.getall('foo'):
+            assert isinstance(prop.value, str)
+
+    def test_getall_iter_list(self, props):
+        props.add('foo', 'a')
+        props.add('foobar', 'b')
+        res = list(props.getall('foo'))
+        assert len(res) == 2
+        for prop in res:
+            assert isinstance(prop.value, str)
+
     def test_getall_prefix(self, props):
         props.add('foo', 'a')
         props.add('foobar', 'b')