Handle case of zero inputs in pipeline connections.

Prerequisite inputs can have zero entries, and should pass checks in this case.
lsst · Dec 10, 2019 · 5a4e04a · 5a4e04a
1 parent 3dc8cbe
commit 5a4e04a
Showing 1 changed file with 3 additions and 1 deletion.
diff --git a/python/lsst/pipe/base/connections.py b/python/lsst/pipe/base/connections.py
@@ -424,8 +424,10 @@ def buildDatasetRefs(self, quantum: Quantum) -> typing.Tuple[InputQuantizedConne
                     # Unpack arguments that are not marked multiples (list of
                     # length one)
                     if not attribute.multiple:
-                        if len(quantumInputRefs) != 1:
+                        if len(quantumInputRefs) > 1:
                             raise ScalarError(attributeName, len(quantumInputRefs))
+                        if len(quantumInputRefs) == 0:
+                            continue
                         quantumInputRefs = quantumInputRefs[0]
                     # Add to the QuantizedConnection identifier
                     setattr(refs, attributeName, quantumInputRefs)