1 files changed, 18 insertions, 2 deletions
diff --git a/buildstream/_yaml.py b/buildstream/_yaml.py
index 85410caf2..7cf743521 100644
--- a/buildstream/_yaml.py
+++ b/buildstream/_yaml.py
@@ -305,6 +305,18 @@ def node_get_provenance(node, key=None, indices=None):
     return provenance
 
 
+# Helper to use utils.sentinel without unconditional utils import,
+# which causes issues for completion.
+#
+# Local private, but defined here because sphinx appears to break if
+# it's not defined before any functions calling it in default kwarg
+# values.
+#
+def _get_sentinel():
+    from .utils import _sentinel
+    return _sentinel
+
+
 # node_get()
 #
 # Fetches a value from a dictionary node and checks it for
@@ -326,10 +338,10 @@ def node_get_provenance(node, key=None, indices=None):
 # Note:
 #    Returned strings are stripped of leading and trailing whitespace
 #
-def node_get(node, expected_type, key, indices=None, default_value=None):
+def node_get(node, expected_type, key, indices=None, default_value=_get_sentinel()):
     value = node.get(key, default_value)
     provenance = node_get_provenance(node)
-    if value is None:
+    if value is _get_sentinel():
         raise LoadError(LoadErrorReason.INVALID_DATA,
                         "{}: Dictionary did not contain expected key '{}'".format(provenance, key))
 
@@ -341,6 +353,10 @@ def node_get(node, expected_type, key, indices=None, default_value=None):
             value = value[index]
             path += '[{:d}]'.format(index)
 
+    # We want to allow None as a valid value for any type
+    if value is None:
+        return None
+
     if not isinstance(value, expected_type):
         # Attempt basic conversions if possible, typically we want to
         # be able to specify numeric values and convert them to strings,