Problems with $lookup function in Telegraf json_transformation derived from jsonata-go

[iserranoe]

I recently had a problem with a json transformation using jsonata in Telegraf. The transformation is the following:

$each($merge([metrics.fields]), function($value, $key) {{
    "key": $key,
    "value": $value
  }}) ~> $reduce(function($acc, $entry) {(
    $contains($entry.key, "__")
      ? (
        $outerLevelKey := $split($entry.key, "__")[0];
        $innerLevelKey := $split($entry.key, "__")[1];        
        $merge([$acc, { 
          $outerLevelKey: $merge([
            $lookup($acc, $outerLevelKey), 
            { $innerLevelKey:$entry.value } 
          ])
        }])
      )
      : $merge([$acc, { $entry.key: $entry.value }])
  )}, {})

That works perfectly in the simulator https://try.jsonata.org/5aN2vrMY3, but when used in Telegraf it doesn't work and I found the problematic function is $lookup($acc, $outerLevelKey), since using $acc.PressSPM instead doesn't cause any problem.

I first asked in Telegraf but they say the issue seems to be in the upstream library they are using, i.e. jsonata-go.

influxdata/telegraf#14069

Also, if anyone knows an alternative way to do the transformation, I'd really appreciate it.

Thanks a lot

[tbal999]

$each($merge([metrics.fields]), function($value, $key) {{ "key": $key, "value": $value }}) ~> $reduce(function($acc, $entry) {( $contains($entry.key, "__") ? ( $outerLevelKey := $split($entry.key, "__")[0]; $innerLevelKey := $split($entry.key, "__")[1]; $merge([$acc, { $outerLevelKey: $merge([ {"key": $lookup($acc, $outerLevelKey)}.key, { $innerLevelKey: $entry.value } ]) }]) ) : $merge([$acc, { $entry.key: $entry.value }]) )}, {})

the above works for your requirement