How to select field with reserved characters?

[halmartin]

Hello, thank you for this useful project, I have been using it for many years to read sensor data from Tasmota and Espurna sensors.

I have the following problem: I have a tasmota device which sends a sensor reading with a field that contains the reserved character .:

2023-12-02 13:20:52,756 DEBUG: mqtt_on_message tele/tasmota/tasmota_16268C/SENSOR b'{"Time":"2023-12-02T14:20:52","VINDRIKTNING":{"PM2.5":5}}'
2023-12-02 13:20:52,757 WARNING: different number of fields
2023-12-02 13:20:52,758 WARNING: empty fields

I am interested in transporting the value of field PM2.5 to influxdb, my config.yaml is the following:

  - measurement: pmtwodotfive
    topic: tele/tasmota/+/SENSOR
    fields:
      value: $.payload.VINDRIKTNING.'PM2.5'
    tags:           
      id: $.topic[2]

How should I properly declare the path of .payload.VINDRIKTNING.PM2.5? The above configuration is not working for me.

If I am understanding the documentation of jsonpath-ng correctly, single or double quotes should be sufficient to select a field with special characters:

Syntax	Meaning
fieldname	the field fieldname (from the “current” object)
"fieldname"	same as above, for allowing special characters in the fieldname
'fieldname'	ditto