Derived data plugin doesn't always generate paths if the source data came from another plugin

[fabdrol]

Situation I have a plugin which generates SK paths. I use this to "inject" certain data into my SK setup (such as the distance between the keel and the depth transducer). I have set up signalk-derived-data to generate depth.belowKeel.

Expected behaviour I expect to see depth values on the path depth.belowKeel.

Actual behaviour depth.belowKeel is never generated

Notes If I restart (untick and tick active) signalk-derived-data, the plugin starts generating data for depth.belowKeel. The issue thus only occurs if both plugins are started during the startup procedure of Node server.

Versions Latest versions of signals-derived-data (1.24.3) and signalk-server-node (1.29) at the time of writing.

[fabdrol]

My guess is that the problem is caused by this line: https://github.com/SignalK/signalk-derived-data/blob/master/calcs/depthBelowKeel2.js#L4

The calculation takes the value for environment.depth.transducerToKeel.value only once; at start-up. This is problematic in my use case, and in situations where a vessel has a lifting keel with a sensor that informs environment.depth.transducerToKeel.value.

[fabdrol]

Just tested this, works for depth below keel