Paul created TINKERPOP-3294:
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Summary: AddPropertyStep does not capture the old property for
EventStrategy when cardinality is not specified
Key: TINKERPOP-3294
URL: https://issues.apache.org/jira/browse/TINKERPOP-3294
Project: TinkerPop
Issue Type: Bug
Components: process
Affects Versions: 3.8.2, 3.7.7
Reporter: Paul
Fix For: 3.7.8, 3.8.3
When EventStrategy is configured, AddPropertyStep calls
captureRemovedProperty() to find the property being replaced, so it can be
passed to vertexPropertyChanged() as the old value.
captureRemovedProperty() checks the {{cardinality}} field of the step. That
field is only set when the cardinality is given explicitly in the traversal,
e.g. {{{}property(single, "name", "x"){}}}. With {{property("name", "x")}} it
is null, so neither the {{single}} nor the {{set}} branch is taken and the old
value is always reported as empty.
The step already falls back to
{{graph.features().vertex().getCardinality(key)}} when it writes the property
(see TINKERPOP-2159), but that fallback is not used by captureRemovedProperty().
To reproduce, with TinkerGraph (default cardinality {{{}single{}}}):
{code:java}
MutationListener listener = ...; // records oldValue in vertexPropertyChanged
GraphTraversalSource g = traversal().withEmbedded(graph)
.withStrategies(EventStrategy.build().addListener(listener).create());
g.addV().property("name", "a").iterate();
g.V().property("name", "b").iterate();
// oldValue received by the listener is vp[empty], expected vp[name->a]
{code}
With {{property(single, "name", "b")}} the old value is reported correctly.
The fix is to compute the effective cardinality once and pass it to
captureRemovedProperty(). On 3.8-dev the fallback is computed after the call to
captureRemovedProperty(), so it also needs to be moved up. The code differs
between the two branches, so I plan to open one PR for 3.7-dev and one for
3.8-dev.
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