Github user neykov commented on a diff in the pull request: https://github.com/apache/brooklyn-server/pull/141#discussion_r63916684 --- Diff: core/src/main/java/org/apache/brooklyn/enricher/stock/AbstractTransformer.java --- @@ -59,27 +72,55 @@ public void setEntity(EntityLocal entity) { super.setEntity(entity); this.producer = getConfig(PRODUCER) == null ? entity: getConfig(PRODUCER); - this.sourceSensor = (Sensor<T>) getRequiredConfig(SOURCE_SENSOR); + this.sourceSensor = (Sensor<T>) getConfig(SOURCE_SENSOR); Sensor<?> targetSensorSpecified = getConfig(TARGET_SENSOR); + List<? extends Sensor<?>> triggerSensorsSpecified = getConfig(TRIGGER_SENSORS); + List<? extends Sensor<?>> triggerSensors = triggerSensorsSpecified != null ? triggerSensorsSpecified : ImmutableList.<Sensor<?>>of(); this.targetSensor = targetSensorSpecified!=null ? (Sensor<U>) targetSensorSpecified : (Sensor<U>) this.sourceSensor; - if (producer.equals(entity) && targetSensorSpecified==null) { + if (targetSensor == null) { + throw new IllegalArgumentException("Enricher "+JavaClassNames.simpleClassName(this)+" has no "+TARGET_SENSOR.getName()+", and it cannot be inferred as "+SOURCE_SENSOR.getName()+" is also not set"); + } + if (sourceSensor == null && triggerSensors.isEmpty()) { + throw new IllegalArgumentException("Enricher "+JavaClassNames.simpleClassName(this)+" has no "+SOURCE_SENSOR.getName()+" and no "+TRIGGER_SENSORS.getName()); + } --- End diff -- Does it make sense to use `enricher.triggerSensors` with anything else than `targetValue`? Probably not, and as you comment would be dangerous to allow arbitrary transformers due to casting issues.
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