Jason Plurad created TINKERPOP-1504:
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             Summary: MutationListener doesn't provide property key on property 
additions
                 Key: TINKERPOP-1504
                 URL: https://issues.apache.org/jira/browse/TINKERPOP-1504
             Project: TinkerPop
          Issue Type: Improvement
          Components: process
    Affects Versions: 3.2.2, 3.1.4
            Reporter: Jason Plurad


The signatures for 
[MutationListener|https://github.com/apache/tinkerpop/blob/3.1.4/gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/util/event/MutationListener.java#L58]
 property changes look like this:

* {{public void vertexPropertyChanged(final Vertex element, final Property 
oldValue, final Object setValue, final Object... vertexPropertyKeyValues);}}

* {{public void edgePropertyChanged(final Edge element, final Property 
oldValue, final Object setValue);}}

* {{public void vertexPropertyPropertyChanged(final VertexProperty element, 
final Property oldValue, final Object setValue);}}

These methods are used when a property is *added* and when a property is 
*changed*. See usage in 
[AddPropertyStep|https://github.com/apache/tinkerpop/blob/3.1.4/gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/sideEffect/AddPropertyStep.java#L93-L98].
 When a vertex property is added, the {{oldValue}} is {{null}}, so there is no 
way for the listener to get the {{String key}} of the added property.

I can think of a few options here, all of which would be breaking changes:
# Pass a non-null {{Property}} as the {{oldValue}} that has the property 
{{key}} but a {{null}} property value. The listener would get the property 
value from {{setValue}}.
# Add a {{final String key}} to the signatures above.
# Change the {{setValue}} to be {{final Property setValue}} so that the key can 
be gathered from the new value.
# Add new methods on {{MutationListener}} for {{vertexPropertyAdded()}}, 
{{edgePropertyAdded()}}, and {{vertexPropertyPropertyAdded()}}.



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