It sound like you just want the computed value just for the purpose of returning it calculated instead of the front-end doing the calculation. If this is true and you want to return all the properties as a map, instead of the entire node (the node includes the property map, list of labels, and id), then you could use the following type of query.
match (n)
with properties(n) as props, n.pA+n.pB as pC
return props{.*, pC}
This will return a map of all the node properties, with the addition of your calculated value. If you want a different key, then change it in the ‘with’ statement or change the return statement to
return props{.*, desiredKey: pC}
You can always add the node id and labels to the return statement if those are also desired.
If you really want to return a node, I think you can leverage the virtual nodes in the APOC library to create a virtual node with the properties you want plus your calculated property. This node can be returned in your query. Looks like you can pass the map above to this APOC method: props{.*, pC}.
I tested this. You could do the following:
match (n)
with properties(n) as props, n.pA+n.pB as pC
with props{.*, pC} as map
return apoc.create.vNode([‘label’], map) as node
