perf(terminal): spawn the shell off the main thread (#295)

term_spawn was a synchronous Tauri command, so it ran on the main thread; starting the shell forks the IDE process, which takes tens of milliseconds with a large resident set and froze the UI each time a terminal opened. It is now async like term_is_busy, so the fork runs off the main thread. The frontend already awaited it.

Co-authored-by: brandondurandpro <[email protected]>

src-tauri/src/commands/term.rs

@@ -4,9 +4,11 @@ use ide_terminal::{TerminalInfo, TerminalOptions};
 use tauri::ipc::Channel;
 use tauri::{State, Window};
 
+/// Async to stay off the main thread: forking the IDE (its whole address space)
+/// to start the shell takes tens of milliseconds, a frozen UI if run there.
 #[tauri::command]
 #[specta::specta]
-pub fn term_spawn(
+pub async fn term_spawn(
     window: Window,
     state: State<'_, AppState>,
     options: TerminalOptions,

src/bindings.ts

@@ -504,6 +504,10 @@ export const commands = {
 	vcsChangelistsSave: (changelists: ChangelistState) => typedError<null, IdeError>(__TAURI_INVOKE("vcs_changelists_save", { changelists })),
 	/**  Create Patch › Save to file. */
 	vcsWritePatch: (path: string, patch: string) => typedError<null, IdeError>(__TAURI_INVOKE("vcs_write_patch", { path, patch })),
+	/**
+	 *  Async to stay off the main thread: forking the IDE (its whole address space)
+	 *  to start the shell takes tens of milliseconds, a frozen UI if run there.
+	 */
 	termSpawn: (options: TerminalOptions, onOutput: Channel<string>) => typedError<TerminalInfo, IdeError>(__TAURI_INVOKE("term_spawn", { options, onOutput })),
 	termWrite: (id: TerminalId, data: string) => typedError<null, IdeError>(__TAURI_INVOKE("term_write", { id, data })),
 	termResize: (id: TerminalId, cols: number, rows: number) => typedError<null, IdeError>(__TAURI_INVOKE("term_resize", { id, cols, rows })),