Template variable error: 'value_json' is undefined - mqtt

[TheLordVader (Anders)]

The sensor is correctly sending the JSON payload, and MQTT subscriptions running on my desktop are receiving the updates, but the value is never updated on the Home Assistant dashboard (the state remains as the literal “Unknown”). Value updates correct if I subscribe to the topic in Mosquitto.

Logger: homeassistant.helpers.template
Source: helpers/template.py:1834
First occurred: 12:31:50 (4933 occurrences)
Last logged: 13:51:06

Template variable error: 'value_json' is undefined when rendering '{{ value_json.wgust10 }}'
Template variable error: 'value_json' is undefined when rendering '{{ value_json.windavg10m }}'
Template variable error: 'value_json' is undefined when rendering '{{ value_json.avgbearing }}'
Template variable error: 'value_json' is undefined when rendering '{{ value_json.press }}'
Template variable error: 'value_json' is undefined when rendering '{{ value_json.windspeed }}'

these are example of my sensors, in sensors.yaml:

- platform: mqtt
  state_topic: "CumulusMX/Interval"
  name: "VP2 pressure"
  unique_id: 'a811af34-8d0a-4e49-ac49-5e16f17444ae'
  unit_of_measurement: "hPa"
  icon: mdi:arrow-up-down
  value_template: "{{ value_json.press }}"
- platform: mqtt
  state_topic: "CumulusMX/DataUpdate"
  name: "VP2 windspeed"
  unique_id: '4ddff28e-c36f-4528-aed4-f0dbe8382974'
  unit_of_measurement: "m/s"
  icon: mdi:weather-windy
  value_template: "{{ value_json.windspeed }}"

[tom_l]

@TheLordVader

The sensor is correctly sending the JSON payload

Can we see a copy of the payload(s)?

[TheLordVader (Anders)]

Sure:

{"topics": [
    {
        "topic": "CumulusMX/IntervalUpdate",
        "data": "{\"time\":\"<#timehhmmss>\",\"press\":<#press rc=y>,\"temp\":<#temp rc=y>,\"tempin\":<#intemp rc=y>,\"tempavg24\":<#avgtemp rc=y>,\"apptemp\":<#apptemp rc=y>,\"tempchangeh\":<#TempChangeLastHour rc=y>,\"raintoday\":<#rfall rc=y>,\"rainmonth\":<#rmonth rc=y>,\"rainratetoday\":<#rrate rc=y>,\"humidity\":<#hum>,\"humidityin\":<#inhum>,\"avgbearing\":<#avgbearing>,\"windavg10m\":<#wspeed rc=y>,\"wgust10\":<#wgust rc=y>}",
        "retain": true
    }
]}

[TheLordVader (Anders)]

Message received in Mosquitto broker:

[TheLordVader (Anders)]

Tried this without success:

How to purge the retained MQTT messages?

You purge a retained message by publishing an empty string to the topic as a retained message. It’s as simple as that. You can do it directly from Developer tools > Services. In the following screenshot, we are publishing an empty string (represented by two consecutive single quotes) to the topic your/topic/goes/here/ as a retained message (retain: true). [Screenshot from 2021-01-13 21-31-39]

[petro]

Your data is not valid json, that’s why value_json does not exist. All the values are invalid. They need to have quotes.

[petro]

to clarify, this is your data

{
	"time": "<#timehhmmss>",
	"press": < #press rc = y > ,
	"temp": < #temp rc = y > ,
	"tempin": < #intemp rc = y > ,
	"tempavg24": < #avgtemp rc = y > ,
	"apptemp": < #apptemp rc = y > ,
	"tempchangeh": < #TempChangeLastHour rc = y > ,
	"raintoday": < #rfall rc = y > ,
	"rainmonth": < #rmonth rc = y > ,
	"rainratetoday": < #rrate rc = y > ,
	"humidity": < #hum > ,
	"humidityin": < #inhum > ,
	"avgbearing": < #avgbearing > ,
	"windavg10m": < #wspeed rc = y > ,
	"wgust10": < #wgust rc = y >
}

This is what is invalid

Notice how the time’s value is in quotes? "<#timehhmmss>"

Every other value needs to be in quotes in order for that to be valid json.

[koying (Chris B)]

My guess it’s that is some metadata used to configure whatever tool.
The screenshot seems to show valid JSON, but ofc we don’t know unless the OP post a complete payload in text (not image) format.

EDIT: Actually, a random JSON validator tells me numbers like +0.3, with the “+”, is not valid JSON

[petro]

The way he posted the data is confusing. what he posted is valid json, however the topics contents is not. Just take what’s in the data field (remove the exterior quotes) and run it through a json checker. It’s littered with errors.

[petro]

@koying

with the “+”, is not valid JSON

Yep, I see that too. TIL. I guess it makes sense though.

[koying (Chris B)]

…and as HA cannot make up JSON from the payload, value_json is not created, leading to 'value_json' is undefined.
QED

[petro]

It’s interesting, the company I work for purposely outputs +'s on positive numbers. However we are doing that on human readable text files. (It’s a readability thing to reduce mistakes). I would have never thought that was invalid json. Then again, I always have json libraries handle the creation of the numerical format when serializing.

[koying (Chris B)]

I had already encountered that kind of semi-weird 'non valid" error on numbers with explicit “+” signs (not sure it was JSON), so that made me test it.

[petro]

Well, the good news is that if OP wraps all those values in strings, home assistant will convert them to numbers.

[TheLordVader (Anders)]

Thank you all for taking your time!
The sensors has worked for almost a year with “<#timehhmmss>” , but started to drop out recently, random more or less. Yesterday it worked overnight and stopped in the morning.
I use it for my my Davis Vantage Pro 2+ weather station, connected through Cumulus MX software. The template mqtt that shows an example on how to properly config Cumulus MX to send JSON looks like this:

{"topics":[
    {
        "topic": "CumulusMX/Interval",
        "data": "{\"time\":\"<#timehhmmss>\",\"temp\":<#temp rc=y>,\"humidity\":<#hum>,\"wgust\":<#wgust rc=y>}",
        "retain": false
    }
]}

I have set the retain flag to “false” for now, published some empty messages, and for the moment my sensors are receiving data from this below:

{"topics":[
    {
        "topic": "CumulusMX/IntervalUpdate",
        "data": "{\"time\":\"<#timehhmmss>\",\"press\":<#press rc=y>,\"temp\":<#temp rc=y>,\"tempavg24\":<#avgtemp rc=y>,\"apptemp\":<#apptemp rc=y>,\"tempin\":<#intemp rc=y>,\"humidity\":<#hum>,\"humidityin\":<#inhum>,\"raintoday\":<#rfall rc=y>,\"rainmonth\":<#rmonth rc=y>,\"avgbearing\":<#avgbearing>,\"wgust10\":<#wgust rc=y>,\"windavg10m\":<#wspeed rc=y>}",
        "retain": false
    }
]}

I’m not sure if I need the timestamp, because I am just interested in the weather data.

[koying (Chris B)]

@TheLordVader

Yesterday it worked overnight and stopped in the morning

See above. At least from the image of the payload you showed, the templates will only work as long as tempchangeh decreases. Wrap that one (you can do all actually) between double quotes.

[TermeHansen (Rasmus Lundsgaard)]

I’m having a similar issue I think, but I don’t understand from the comments here what the actual solution was in this case - and if I then can use that.

in my case I have simple dht22 sensor, that I have sending both

$ paho_c_sub -h 192.168.0.4 -t neo2/dht22
{"humidity":"26.420000","temperature":"21.300000"}

and

$ paho_c_sub -h 192.168.0.4 -t neo2/dht22
{"humidity":26.4,"temperature":21.3}

and still in both cases I get:
ERROR (MainThread) [homeassistant.helpers.template] Template variable error: 'value_json' is undefined when rendering '{{ value_json.temperature }}'

from my configuration.yaml

mqtt:
  sensor:
    - name: "DHT22 Temperature"
      state_topic: "neo2/dht22"
      unit_of_measurement: "°C"
      value_template: "{{ value_json.temperature }}"

looking at this: MQTT Sensor - Home Assistant

[Troon]

At least one of those should work, I would have thought — provided your MQTT setup is working. To check, please remove the value_template line altogether, and then share a screenshot of the Developer Tools / States page for the sensor once it has updated. Like this, but for your sensor:

[TermeHansen (Rasmus Lundsgaard)]

Right now on mobile, but in home assistant log I see:

2023-02-14 14:19:34.773 WARNING (MainThread) [homeassistant.components.sensor] Sensor sensor.dht22_temperature has device class None, state class None and unit °C thus indicating it has a numeric value; however, it has the non-numeric value: {"humidity":26.51,"temperature":21.24} (<class 'str'>); Please update your configuration if your entity is manually configured, otherwise create a bug report at https://github.com/home-assistant/core/issues?q=is%3Aopen+is%3Aissue+label%3A%22integration%3A+mqtt%22

And

[Troon]

It looks as though it may be having trouble interpreting the input as valid JSON. Try this:

value_template: "{{ (value|from_json)['temperature'] }}"