Gradually turn on lights.

[Crille]

Following the docs:
In expressions; dynamic groups can be referred to in the groups key of the matchEntities() function, or by passing the group's canonical ID to getEntity(). The former is probably preferable, as it's much easier to read and understand what is going on.
Example in docs:

each e in matchEntities({group:'groups>low_battery_entities'}): e.name
each id in getEntity('groups>low_battery_entities').attributes.sys_group.members: getEntity( id ).name

I set up a Dynamic group:

  - id: groups
    name: Dynamic Group Controller
    enable: true
    implementation: DynamicGroupController
    config:
      groups:
        "EzloDevicesNotResponding2":
          name: Ezlo Devices Not Responding
          select:
            - include_controller: ezlo
            - include_capability: x_ezlo_device
          filter_expression: entity.attributes.x_ezlo_device.reachable != true

But when I try the Expression I get a compilation error

Log:

[latest-22004]2022-01-09T12:24:35.420Z <Engine:NOTICE> [Engine]Engine#1 expression testing has changed; recomputing dependencies
[latest-22004]2022-01-09T12:24:35.421Z <Engine:ERR> [Engine]Engine#1: error evaluating expression testing: [ReferenceError]ReferenceError: Invalid reference to member name of ezlo>device_61baf610129e0725bd9f80f3
[latest-22004]2022-01-09T12:24:35.422Z <Engine:ERR> [Engine]Engine#1: expression: each e in matchEntities({group:'groups>EzloDevicesNotResponding2'}): e.name
[latest-22004]2022-01-09T12:24:35.422Z <Engine:5:Engine.js:960> [Engine]Engine#1: path testing->testing
[latest-22004]2022-01-09T12:24:35.422Z <Engine:CRIT> ReferenceError: Invalid reference to member name of ezlo>device_61baf610129e0725bd9f80f3
ReferenceError: Invalid reference to member name of ezlo>device_61baf610129e0725bd9f80f3
    at _run (/home/homebridge/reactor/common/lexp.js:1411:31)
    at _run (/home/homebridge/reactor/common/lexp.js:1514:41)
    at /home/homebridge/reactor/common/lexp.js:1246:29
    at Array.forEach (<anonymous>)
    at _run (/home/homebridge/reactor/common/lexp.js:1245:28)
    at run (/home/homebridge/reactor/common/lexp.js:1609:22)
    at Object.evaluate (/home/homebridge/reactor/common/lexp.js:1645:20)
    at Engine._eval_expr (/home/homebridge/reactor/server/lib/Engine.js:958:280)
    at Engine.notify (/home/homebridge/reactor/server/lib/Engine.js:644:142)
    at /home/homebridge/reactor/server/lib/MessageBus.js:106:223
[latest-22004]2022-01-09T12:24:35.424Z <Engine:5:Engine.js:1000> [Engine]Engine#1 set global testing; value=(object)(null)

When not referring to e.name It's an array with three members

latest-22004-6d6c6b7 bare metal installation.

What I'm I doing wrong?

[toggledbits]

matchEntities() returns a list (array) of canonical IDs, not entity objects. You need:

each id in matchEntities({group:'groups>low_battery_entities'}): getEntity( id ).name

[Crille]

I suspected that, then consider this post a PR to change the example in the docs. Thank you!

[toggledbits]

This is the example in the docs. I'm not seeing any issue here:

        sensors = matchEntities( { controller: 'vera',
          capability: [ 'binary_sensor', 'value_sensor' ] } )

        low_battery = each e in sensors:
                        getEntity( e ).attributes.battery_power?.level < 0.5 ? e : null

sensors is handled as an array of canonical IDs by the second expression. Is there another place in the docs you are referring to that I'm not thinking of?

[Crille]

Yes, at the bottom of the page under "Using Dynamic Groups".
Also referred to at the beginning of my first post.

[toggledbits]

OK. I was looking at the Expressions docs.

Edit: changes will make their way into the next release, along with strong messaging that dynamic groups should be used in preference to matchEntities() for group filtering (you can still use it to get the group members, but let DynamicGroupController do the hard work). DGC is much more efficient (and flexible) in its filtering, by design.

[Crille]

So to get the names in an Expression for a notification, is it still preferred to use do..done or just getEntity(id).name?

[toggledbits]

Confusing. The only way to get the name (currently) is through getEntity(). The do...done statement doesn't enter into it; it's just a language construction that may or may not be needed in the expression as written. I think you're thinking of each...in, which is how you iterate over an array, so yes, if you have an array of entity IDs, you'll need each...in and getEntity() together to make a list of them.

[Crille]

Sorry for assuming you remember every post you ever made
I was referring to this excellent advice
I guess it’s not necessary when I only do one getEntity for the name.

[toggledbits]

Ah, yes... if you need to reuse the fetched entity several times, it's definitely better to use a do...done block as the loop body and keep the result of getEntity() in a local variable, so you're only doing that fetch one time. You can then use the local variable as many times as needed... a cache of sorts. I'm with you...