_yaml: Never create base 'Node' directly

We shouldn't have to create normal nodes ever. Let's ensure we don't

2 files changed, 8 insertions, 5 deletions

diff --git a/src/buildstream/_yaml.pyx b/src/buildstream/_yaml.pyx
index e69ff8ee9..6a0080b37 100644
--- a/src/buildstream/_yaml.pyx
+++ b/src/buildstream/_yaml.pyx
@@ -521,13 +521,16 @@ cdef class Representer:
 
 
 cdef Node _create_node(object value, int file_index, int line, int column):
-    if type(value) in [bool, str, type(None), int]:
+    cdef type_value = type(value)
+
+    if type_value in [bool, str, type(None), int]:
         return ScalarNode(value, file_index, line, column)
-    elif type(value) is dict:
+    elif type_value is dict:
         return MappingNode(value, file_index, line, column)
-    elif type(value) is list:
+    elif type_value is list:
         return SequenceNode(value, file_index, line, column)
-    return Node(value, file_index, line, column)
+    raise ValueError(
+        "Node values can only be 'list', 'dict', 'bool', 'str', 'int' or None. Not {}".format(type_value))
 
 
 # Loads a dictionary from some YAML
diff --git a/src/buildstream/testing/_sourcetests/track.py b/src/buildstream/testing/_sourcetests/track.py
index 08173e79b..58679e9f1 100644
--- a/src/buildstream/testing/_sourcetests/track.py
+++ b/src/buildstream/testing/_sourcetests/track.py
@@ -327,7 +327,7 @@ def test_track_include(cli, tmpdir, datafiles, ref_storage, kind):
         # Get the first source from the sources list
         new_source = sources_list.mapping_at(0)
         assert 'ref' in new_source
-        assert ref == new_source.get_scalar('ref').as_str()
+        assert ref == new_source.get_str('ref')
 
 
 @pytest.mark.datafiles(DATA_DIR)