feat(core): implement `CommandArg` for `AppHandle` (#2037)

.changes/command-app-handle.md

@@ -0,0 +1,5 @@
+---
+"tauri": patch
+---
+
+Allow accessing an `AppHandle` instance on a command through dependency injection.

core/tauri/src/app.rs

@@ -9,6 +9,7 @@ pub(crate) mod tray;
 use crate::{
   api::assets::Assets,
   api::config::{Config, WindowUrl},
+  command::{CommandArg, CommandItem},
   hooks::{InvokeHandler, OnPageLoad, PageLoadPayload, SetupHook},
   manager::{Args, WindowManager},
   plugin::{Plugin, PluginStore},
@@ -19,7 +20,7 @@ use crate::{
     Dispatch, MenuId, Params, RunEvent, Runtime,
   },
   sealed::{ManagerBase, RuntimeOrDispatch},
-  Context, Invoke, Manager, StateManager, Window,
+  Context, Invoke, InvokeError, Manager, StateManager, Window,
 };
 
 use tauri_utils::PackageInfo;
@@ -133,6 +134,13 @@ impl<P: Params> Clone for AppHandle<P> {
   }
 }
 
+impl<'de, P: Params> CommandArg<'de, P> for AppHandle<P> {
+  /// Grabs the [`Window`] from the [`CommandItem`] and returns the associated [`AppHandle`]. This will never fail.
+  fn from_command(command: CommandItem<'de, P>) -> Result<Self, InvokeError> {
+    Ok(command.message.window().app_handle)
+  }
+}
+
 impl<P: Params> AppHandle<P> {
   /// Removes the system tray.
   #[cfg(all(windows, feature = "system-tray"))]

docs/usage/guides/command.md

@@ -137,6 +137,19 @@ async fn my_custom_command(window: tauri::Window) {
 }
 ```
 
+## Accessing an AppHandle in Commands
+
+Commands can access an `AppHandle` instance:
+
+```rust
+#[tauri::command]
+async fn my_custom_command(app_handle: tauri::AppHandle) {
+  let app_dir = app_handle.path_resolver().app_dir();
+  use tauri::GlobalShortcutManager;
+  app_handle.global_shortcut_manager().register("CTRL + U", move || {});
+}
+```
+
 ## Accessing managed state
 
 Tauri can manage state using the `manage` function on `tauri::Builder`.