Using rust-attr with feature="serde" not working

[SKittan]

I'm trying to test saving and loading a Slint struct by serde in Rust. I found a pull request about this topic and tested the code for my self.

The Slint file has only a small test struct and a window to display it:

@rust-attr(cfg_attr(feature="serde", derive(Serialize, Deserialize)))
export struct winData {
    number: int,
    text: string
}

export component mainWindow inherits Window {
    in-out property <winData> data;

    VerticalLayout {
        padding: 10px;
        Text {text: data.number;}
        Text {text: data.text;}
    }
}

The rust code is creating the window and loading a sample file:

use std::fs;

slint::slint!(import { mainWindow } from "./src/main.slint";);

fn main() {
    let main_window = mainWindow::new().unwrap();

    let fname = "../../data.json";
    match fs::read_to_string(&fname) {
        Err(_) => println!("Error open TMx devices file: {:?}",
                           &fname),
        Ok(data) => {
            match serde_json::from_str::<winData>(&data) {
                Ok(res) => {
                    main_window.set_data(res);
                },
                Err(e) => {
                    println!("Error reading TMx devices config: \
                             {:?}", e);
                }
        }}};

    main_window.run();
}

The compilation of this project fails with the following error:

error[E0277]: the trait bound winData: serde::de::Deserialize<'_> is not satisfied
--> src\main.rs:13:19
|
13 | match serde_json::from_str::(&data) {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait serde::de::Deserialize<'_> is not implemented for winData

[ogoffart]

Since your crate probably doesn't have a serde feature, you can try something like
@rust-attr(derive(Serialize, Deserialize)) (without the cfg_attr)

[SKittan]

This is the point I started from and leads to the following compiler error:

error[E0277]: the trait bound slint::SharedString: Deserialize<'_> is not satisfied
--> src\main.rs:3:1
|
3 | slint::slint!(import { mainWindow } from "./src/main.slint"...
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait Deserialize<'_> is not implemented for slint::SharedString

[ogoffart]

ah, you need to enable the serde feature of the slint crate.

[SKittan]

Can you please provide a small example how to do this?

Edit:
To clarify my question: I can find the following feature flags in the Slint rust docs:

• compat-1-0
• std
• gettext
• libm
• log
• software-renderer-systemfonts
• unsafe-single-threaded
• accessibility

When I try slint = { version = "1", features = ["serde"] } in my cargo.toml file, I get an error. Do I understand something wrong or is the serde feature not available yet?

[SKittan]

In case someone else has the same challenge:

The serde feature of Slint can be activated with the following dependency entry in the Cargo.toml file:
i-slint-core = { version = "1.1", features = ["serde"] }

Afterwards the serde derive macros can be used in Slint files, as described in the documentation:
@rust-attr(derive(serde::Serialize, serde::Deserialize))

The activation of the serde feature will enable Serialization / Deserialization of the SharedString data type.

[ogoffart]

You don't want to add i-slint-core in your Cargo.toml because thats's private API and it can break

I thought we had a serde feature exposed in the slint crate, but apparently we did not add that.
So i'm adding it in #3326