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Merged
merged 1 commit into from
Apr 12, 2025
Merged

Improve MQTT template docs on handling null values #38485

merged 1 commit into from
Apr 12, 2025

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jbouwh
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@jbouwh jbouwh commented Apr 11, 2025 •
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Proposed change

Improve MQTT template docs on handling null / None values. For MQTT sensor this was not correctly documented.

The current docs say null could be used to set the MQTT sensors state to unknown. That is only when a value in a JSON payload is rendered. In fact None is expected, either from a rendering template or as payload.

Type of change

  • Spelling, grammar or other readability improvements (current branch).
  • Adjusted missing or incorrect information in the current documentation (current branch).
  • Added documentation for a new integration I'm adding to Home Assistant (next branch).
  • Added documentation for a new feature I'm adding to Home Assistant (next branch).
  • Removed stale or deprecated documentation.

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  • This PR uses the correct branch, based on one of the following:
    • I made a change to the existing documentation and used the current branch.
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Summary by CodeRabbit

  • Documentation
    • Enhanced templating documentation by expanding the JSON payload example to include humidity data with a corresponding template snippet.
    • Clarified the MQTT sensor configuration description to accurately reflect how "None" values are rendered when processing JSON payloads.

@home-assistant home-assistant bot added the current This PR goes into the current branch label Apr 11, 2025
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📝 Walkthrough

Walkthrough

The pull request updates documentation examples and descriptions. In the templating configuration file, an additional JSON key ("humidity": null) is added to the payload example along with a corresponding template snippet ({{ value_json.humidity }}). In the MQTT sensor integration documentation, the description for the state_topic field is adjusted to indicate that a value of 'None' results in an unknown sensor state and to clarify the rendering behavior of null values when processed with a value_template.

Changes

File Change Summary
source/_docs/.../templating.markdown Added the "humidity": null key to the JSON payload and introduced a new template example ({{ value_json.humidity }}) for humidity data.
source/_integrations/.../sensor.mqtt.markdown Updated the state_topic field description to specify that a 'None' value sets the sensor to an unknown state and clarified JSON parsing behavior.

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Actionable comments posted: 0

🧹 Nitpick comments (1)
source/_integrations/sensor.mqtt.markdown (1)

204-205: Improve Description of Null/None Handling in State Topic

The updated description now correctly explains that:

  • An empty string ('') is ignored,
  • A 'None' value sets the sensor to an unknown state, and
  • When using a value_template for JSON payloads, a null value renders as 'None'.

One nitpick: the hyperlink syntax has double parentheses. Consider changing

- a null value in the JSON [will be rendered as]((/docs/configuration/templating/#using-value-templates-with-mqtt)) 'None'
+ a null value in the JSON [will be rendered as](/docs/configuration/templating/#using-value-templates-with-mqtt) 'None'

to improve consistency.

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📥 Commits

Reviewing files that changed from the base of the PR and between 4836394 and a5f9ad2.

📒 Files selected for processing (2)
  • source/_docs/configuration/templating.markdown (1 hunks)
  • source/_integrations/sensor.mqtt.markdown (1 hunks)
🔇 Additional comments (1)
source/_docs/configuration/templating.markdown (1)

1639-1645: Clarify JSON Null Handling in Templating Example

The added JSON payload now includes "humidity": null, and the accompanying note clearly explains that when processed by a value_template, the null value is rendered as None. This update improves clarity and helps users understand the template’s behavior with null values.

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Hey there @emontnemery, @bdraco, mind taking a look at this feedback as it has been labeled with an integration (mqtt) you are listed as a code owner for? Thanks!

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c0ffeeca7
c0ffeeca7 approved these changes Apr 12, 2025
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Thank you, @jbouwh 👍

@github-project-automation github-project-automation bot moved this from Todo to Approved in Documentation PRs Apr 12, 2025
@c0ffeeca7 c0ffeeca7 merged commit 4144b06 into current Apr 12, 2025
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@c0ffeeca7 c0ffeeca7 deleted the mqtt-improve-docs-template-null-handling branch April 12, 2025 04:44
@github-project-automation github-project-automation bot moved this from Approved to Done in Documentation PRs Apr 12, 2025
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MQTT sensor: undocumented special meaning of value 'None'
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