Builder with nested Linear Layout?

[michalfita]

I load this example YML code of my own making:

LinearLayout:
  orientation: horizontal
  children:
    - SelectView:
        with:
          - panel
        items:
          - "Lorem ipsum"
          - "Dolor sit amet"
          - "Consectetur adipiscing elit"
    - DummyView:
    - LinearLayout:
      orientation: vertical
      with:
        - panel
      children:
        - Button:
            label: Foobar
        - Button:
            label: Quit
            callback: $Cursive.quit

via the builder pattern from examples (v0.21.1 with builder feature enabled).

The second inner layout doesn't appear at all. With simpler example with just a button in the root layout, the button appears. There are no errors.

Note

Use of builder could be better documented, especially sections in docs.rs for views module would help a lot.

[gyscos]

Hi, and thanks for the report!

I suspect the issue here is the ambiguity with yaml regarding list of objects. The child must have a single LinearLayout key, with the config for that view. Your example code instead has a large dict with everything, including a LinearLayout key associated to a null value.

Here's what you should probably do instead:

LinearLayout:
  orientation: horizontal
  children:
    - SelectView:
        with:
          - panel
        items:
          - "Lorem ipsum"
          - "Dolor sit amet"
          - "Consectetur adipiscing elit"
    - DummyView:
    - LinearLayout:
        orientation: vertical
        with:
          - panel
        children:
          - Button:
              label: Foobar
          - Button:
              label: Quit
              callback: $Cursive.quit

I agree yaml can be very confusing for this specific case. In your example, it sees a Linear layout with an empty config, and ignores the rest of the keys. We should be able to error or warn when there's extra keys like this.

[michalfita]

Thanks for quick reply. I think I realized that in the mean time as well.

However, with this code I get the error:

Error: View build failure: BlueprintFailed("LinearLayout", ResolveFailed { var_failure: InvalidConfig { message: "Expected variable as $key; but found LinearLayout.", config: Object {"LinearLayout": Object {"children": Array [Object {"Button": Object {"label": String("Foobar")}}, Object {"Button": Object {"callback": String("$Cursive.quit"), "label": String("Quit")}}], "orientation": String("vertical"), "with": Array [String("panel")]}} }, config_failure: BlueprintFailed("LinearLayout", ResolveFailed { var_failure: InvalidConfig { message: "Expected variable as $key; but found Button.", config: Object {"Button": Object {"label": String("Foobar")}} }, config_failure: BlueprintFailed("Button", ResolveFailed { var_failure: CouldNotLoad { expected_type: "alloc::sync::Arc<dyn core::ops::function::Fn(&mut cursive_core::cursive_root::Cursive) + core::marker::Send + core::marker::Sync>", config: Null }, config_failure: CouldNotLoad { expected_type: "alloc::sync::Arc<dyn core::ops::function::Fn(&mut cursive_core::cursive_root::Cursive) + core::marker::Send + core::marker::Sync>", config: Null } }) }) })

What worries me is that crate::blueprint in linear_layout.rs is commented out.

[gyscos]

I also absolutely agree with the need for better doc. The builder module started as an experiment to see what was possible, and now that it's looking like it could actually be useful, having first-class support for it, including better docs, would be great.

[gyscos]

It looks like it's not happy about the button lacking a callback. Will check if it's optional, and if we can make it optional if not.

[gyscos]

Yes I'm pretty sure the problem is that the callback for buttons is currently non optional. I think there's a noop callback we can use here, will check. Edit: looks like there's none yet.

I'll add one ; in the meantime, you should also be able to register new functions from your code (though it isn't very ergonomic yet):

// Registers the `$Cursive.noop` function
crate::fn_blueprint!("Cursive.noop", |_config, _context| {
    let cb: std::sync::Arc<dyn Fn(&mut Cursive) + Send + Sync> = std::sync::Arc::new(|s| s.noop());
    Ok(cb)
});

I hope I'll be able to bring a similar declarative definition of functions, but for now it's the very manual way.

What worries me is that crate::blueprint in linear_layout.rs is commented out.

The declarative blueprint is commented out, but the manual_blueprint underneath should be working.

[michalfita]

Any way to improve error messages to point at actual root cause?

[gyscos]

The error is currently very hard to read, it's not something I've spent enough time on yet (I really should!).

In particular, while it currently mentions that it failed while running the Button blueprint, it's not currently indicating which field actually failed (the callback).

I'll see if I can improve the Debug implementation to properly show the chain of errors with indentation, it should also help a bit. Especially to focus on the tail of the chain.