[docs] Splashscreen example doesn't work out of the box

[jacobq]

Disclaimer: I'm brand new to Rust and to Tauri; just spun up my first app with the beta today.

The docs provide some example code to illustrate how to make a "splash screen" (separate window / webview) and display it while the main application loads. However, when I tried it I encountered errors.

Error messages during compilation

   Compiling app v0.1.0 (/home/jquant/tmp/tauri-app-hello/src-tauri)
error: only a single item `async` is currently allowed
  --> src/main.rs:10:18
   |
10 | #[tauri::command(with_window)]
   |                  ^^^^^^^^^^^
...
23 |     .invoke_handler(tauri::generate_handler![close_splashscreen])
   |                     -------------------------------------------- in this macro invocation
   |
   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0405]: cannot find trait `Params` in this scope
  --> src/main.rs:11:26
   |
11 | fn close_splashscreen<M: Params>(window: tauri::Window<M>) {
   |                          ^^^^^^ not found in this scope
   |
help: consider importing this trait
   |
11 | use tauri::Params;
   |

error: aborting due to 2 previous errors

Then I tried adding use tauri::Params; (at the top of main.rs)

Second round of error messages

   Compiling app v0.1.0 (/home/jquant/tmp/tauri-app-hello/src-tauri)
error: only a single item `async` is currently allowed
  --> src/main.rs:11:18
   |
11 | #[tauri::command(with_window)]
   |                  ^^^^^^^^^^^
...
24 |     .invoke_handler(tauri::generate_handler![close_splashscreen])
   |                     -------------------------------------------- in this macro invocation
   |
   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0599]: no method named `get_webview` found for struct `Window<M>` in the current scope
  --> src/main.rs:14:36
   |
14 |   if let Ok(splashscreen) = window.get_webview("splash") {
   |                                    ^^^^^^^^^^^ method not found in `Window<M>`

error[E0599]: no method named `get_webview` found for struct `Window<M>` in the current scope
  --> src/main.rs:18:10
   |
18 |   window.get_webview("main").unwrap().show().unwrap();
   |          ^^^^^^^^^^^ method not found in `Window<M>`

error: aborting due to 3 previous errors

For more information about this error, try `rustc --explain E0599`.
error: could not compile `app`

Looking at the API docs, I see window.struct, but it has no get_webview method, so I'm not sure where this functionality is. In fact, doing a GitHub search for get_webview produced exactly 1 result, which was the splash screen example where I obtained the code that doesn't seem to work. Digging a little more, I found a method of the same name in WRY's webview2 source.

yarn tauri info

Operating System - Debian, version 11 X64

Node.js environment
  Node.js - 14.17.3
  @tauri-apps/cli - 1.0.0-beta.5
  @tauri-apps/api - 1.0.0-beta.4

Global packages
  npm - 6.14.13
  yarn - 1.22.5

Rust environment
  rustc - 1.53.0
  cargo - 1.53.0

App directory structure
/front-end
/.idea
/node_modules
/src-tauri
/.git

App
  tauri.rs - 1.0.0-beta.4
  build-type - bundle
  CSP - default-src blob: data: filesystem: ws: wss: http: https: tauri: 'unsafe-eval' 'unsafe-inline' 'self' img-src: 'self'
  distDir - front-end/dist
  devPath - http://localhost:4200/

Done in 3.49s.

FWIW, my code is available at jacobq/tauri-hello-world/tree/broken-splash