JSONata query with '?(expr)' ?? How to?

[maddinRZ]

Hi all,

after I have found out the issue with the JSONpath expression #343 I managed to get JSON data in Grafana. So far so good but sometimes the graphs was broken and after checking the root cause I found out the Web API of our photovoltaic management console is generating the JSON data not in a consistent way.

This means, the arrays are not on the same location on every GET request. For example, one time it is like...

{ "powerDetails": { "timeUnit": "QUARTER_OF_AN_HOUR", "unit": "W", "meters": [ { "type": "Purchased", "values": .....

And one minute later it is like:

{ "powerDetails": { "timeUnit": "QUARTER_OF_AN_HOUR", "unit": "W", "meters": [ { "type": "Consumed", "values": .....

So to fetch the right field into Grafana I used expressions like:

$.powerDetails.meters[?(@.type == "Purchased")].values[*].value

Unfortunately, by design or fault, if there is no current from the PV, the element "value" is not in the array. Here I could use the JSONata expression to fill '0' if the element is missing.

($exists($.powerDetails.meters[3].values[*]."value") ? $.powerDetails.meters[3].values[*]."value" : 0)

This only works if the array '[3]' is actually the current element (here it is named "Production").

How to add/change the JSONata expression to add the 'type' condition?