Clarification on EWW expressions

[DarkSamus9000]

The documentation for EWW expressions is a little sparse, so I had some questions for you here if this is the place to ask them.

I have a widget with an optional attribute. Based on whether or not the attirubute is defined, I'd like the widget to include one of two different other widgets. But code speaks louder than words, so here's a relevant snippet of my eww.yuck:

(defwidget main [?second_monitor]
    (box :orientation "horizontal"
        :space-evenly "true"
        (group_left :second_monitor second_monitor)
        (group_center)
        (group_right)
    )
)

(defwidget group_left [?second_monitor]
    (box :orientation "horizontal"
        :class "group_left"
        :space-evenly "false"
        :halign "left"
        (dashboard)
        {second_monitor ? (workspaces_alt) : (workspaces)}
    )
)

EWW doesn't throw any errors, but this code doesn't produce what I'm expecting.
The widget main is produced, and I can see the group_left widget with its nested dashboard widget, but group_left is not including workspaces_alt or workspaces. It doesn't matter whether I define the attribute second_monitor or not when I create the main widget.

I suppose my primary question regards this line:

        {second_monitor ? (workspaces_alt) : (workspaces)}

Is this the correct way to do what I want? I want to check whether an attribute is defined or not, and depending on that, I want to include a different widget.

[elkowar]

optional arguments default to the value "" IIRC, so the proper way to check if the default value is used is to do second_monitor == "".
Next part: Eww expressions can't "return" other widgets, sadly.
What you want to do for this is do to something along the lines of this

(defwidget group_left [?second_monitor]
    (box :orientation "horizontal"
        :class "group_left"
        :space-evenly "false"
        :halign "left"
        (dashboard)
        (box :visible {second_monitor != ""} (workspaces_alt))
        (box :visible {second_monitor} (workspaces))
    )
)

then you can call it with

(group_left)

or

(group_left :second_monitor true)

[MartyMcFlyInTheSky]

What if I were to call it with (group_left : second_monitor false), wouldn't this also take the {second_monitor != ""} branch?

[ItsTerm1n4l]

how would I write an if statement in eww then?

[Eclextic]

Create a variable and add a ternary operator (in the docs its called a conditional) to dynamically adjust the widgets accordingly!

[ItsTerm1n4l]

Ok, thank you!

[ItsTerm1n4l]

I didn't realise it had to be done in a variable - probably why it didn't work for me.