Add a test for transcoding loops of 1 or more nodes (#3810)

Signed-off-by: Ivan Danov <idanov@users.noreply.github.com>
Signed-off-by: Ahdra Merali <ahdra.merali@quantumblack.com>

kedro/pipeline/pipeline.py

@@ -171,7 +171,8 @@ def __init__(
  try:
  self._toposorter.prepare()
  except CycleError as exc:
- message = f"Circular dependencies exist among these items: {exc.args[1]}"
+ loop = list(set(exc.args[1]))
+ message = f"Circular dependencies exist among the following {len(loop)} item(s): {loop}"
  raise CircularDependencyError(message) from exc
 
  self._toposorted_nodes: list[Node] = []

tests/pipeline/test_pipeline_with_transcoding.py

@@ -5,7 +5,11 @@
 import kedro
 from kedro.pipeline import node
 from kedro.pipeline.modular_pipeline import pipeline as modular_pipeline
-from kedro.pipeline.pipeline import OutputNotUniqueError, _strip_transcoding
+from kedro.pipeline.pipeline import (
+ CircularDependencyError,
+ OutputNotUniqueError,
+ _strip_transcoding,
+)
 
 
 # Different dummy func based on the number of arguments
@@ -177,6 +181,24 @@ def test_duplicates_in_transcoded_outputs(self):
  ]
  )
 
+ def test_transcoding_loop(self):
+ with pytest.raises(CircularDependencyError, match="node1"):
+ modular_pipeline(
+ [
+ node(identity, "A@pandas", "B@pandas", name="node1"),
+ node(identity, "B@spark", "C@spark", name="node2"),
+ node(identity, "C@spark", "A@spark", name="node3"),
+ ]
+ )
+
+ def test_transcoding_self_reference(self):
+ with pytest.raises(CircularDependencyError, match="node1"):
+ modular_pipeline(
+ [
+ node(identity, "A@pandas", "A@spark", name="node1"),
+ ]
+ )
+
 
 class TestComplexPipelineWithTranscoding:
  """