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Add default_entity_id to MQTT HA autodiscovery payload #3970

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Add default_entity_id to MQTT HA autodiscovery payload #3970

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17f11e4
HA MQTT autodiscovery topic update
mekaneck Nov 25, 2025
ad04c34
Fix whitespace
mekaneck Nov 25, 2025
ca91e14
Whitespace again
mekaneck Nov 25, 2025
f5b9582
Whitespace final
mekaneck Nov 25, 2025
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28 changes: 16 additions & 12 deletions code/components/jomjol_mqtt/server_mqtt.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -72,36 +72,40 @@ bool sendHomeAssistantDiscoveryTopic(std::string group, std::string field,
std::string topicFull;
std::string configTopic;
std::string payload;
std::string component;

configTopic = field;

if (group != "" && (*NUMBERS).size() > 1) { // There is more than one meter, prepend the group so we can differentiate them
configTopic = group + "_" + field;
name = group + " " + name;
}
}

/**
* homeassistant needs the MQTT discovery topic according to the following structure:
* <discovery_prefix>/<component>/[<node_id>/]<object_id>/config
* if the main topic is embedded in a nested structure, we just use the last part as node_id
* This means a maintopic "home/test/watermeter" is transformed to the discovery topic "homeassistant/sensor/watermeter/..."
*/
std::string node_id = createNodeId(maintopic);
if (field == "problem") { // Special case: Binary sensor which is based on error topic
topicFull = "homeassistant/binary_sensor/" + node_id + "/" + configTopic + "/config";
component = "binary_sensor";
}
else if (field == "flowstart") { // Special case: Button
topicFull = "homeassistant/button/" + node_id + "/" + configTopic + "/config";
component = "button";
}
else {
topicFull = "homeassistant/sensor/" + node_id + "/" + configTopic + "/config";
component = "sensor";
}

/**
* homeassistant needs the MQTT discovery topic according to the following structure:
* <discovery_prefix>/<component>/[<node_id>/]<object_id>/config
* if the main topic is embedded in a nested structure, we just use the last part as node_id
* This means a maintopic "home/test/watermeter" is transformed to the discovery topic "homeassistant/sensor/watermeter/..."
*/
std::string node_id = createNodeId(maintopic);
topicFull = "homeassistant/" + component + "/" + node_id + "/" + configTopic + "/config";

/* See https://www.home-assistant.io/docs/mqtt/discovery/ */
payload = string("{") +
"\"~\": \"" + maintopic + "\"," +
"\"unique_id\": \"" + maintopic + "-" + configTopic + "\"," +
"\"object_id\": \"" + maintopic + "_" + configTopic + "\"," + // This used to generate the Entity ID
"\"object_id\": \"" + maintopic + "_" + configTopic + "\"," + // Default entity ID; required for HA <= 2025.10
"\"default_entity_id\": \"" + component + "." + maintopic + "_" + configTopic + "\"," + // Default entity ID; required in HA >=2026.4
"\"name\": \"" + name + "\"," +
"\"icon\": \"mdi:" + icon + "\",";

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