From 9847c03d0b7d30e22b9fb88948594a1b6496c229 Mon Sep 17 00:00:00 2001
From: orange-bot <bot@orange.local>
Date: Wed, 14 Oct 2026 21:45:02 +0800
Subject: [PATCH] fix(everest): refuse to install Everest while Celeste is
 running

The Everest install path downloads the package, extracts it over the game
directory and then runs MiniInstaller, but it never checked whether the game
was running. MiniInstaller's own guard (WaitForGameExit) is a no-op when it is
launched this way and EnsureGameIsWriteable only probes Celeste.exe and
Celeste.dll, so a process still holding a native library fails the install
half-way through with a raw IOException on lib64-win-x64\fmod64.dll, leaving
the game with a new Celeste.Mod.mm.dll but the old patched Celeste.dll.

Refuse early like the local package install path does, and append an
actionable hint to that file-in-use error.
---
 src-tauri/src/backend.rs | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/src-tauri/src/backend.rs b/src-tauri/src/backend.rs
index 6dd4097..24a1165 100644
--- a/src-tauri/src/backend.rs
+++ b/src-tauri/src/backend.rs
@@ -5471,6 +5471,21 @@ fn remove_new_keyboard_input(game_path: String) -> Result<(), String> {
     fs::write(path, without_new_keyboard_input_enabled(&content)).map_err(|error| error.to_string())
 }
 
+/// A file the install has to replace was still open in another process. The raw
+/// OS error ("being used by another process") does not tell the user what to do,
+/// and MiniInstaller stops in the middle of the update: tell them that closing
+/// everything that uses the game files and re-running the install is the fix.
+fn with_file_in_use_hint(message: String) -> String {
+    const IN_USE_MARKERS: [&str; 2] = ["being used by another process", "另一个程序正在使用此文件"];
+    if !IN_USE_MARKERS.iter().any(|marker| message.contains(marker)) {
+        return message;
+    }
+    format!(
+        "{message}\n\n请确认游戏已经完全退出（任务管理器里没有 Celeste.exe），然后重新安装一次 Everest。\
+         上一次中断留下的半成品文件会被这次安装覆盖掉。"
+    )
+}
+
 #[tauri::command]
 fn download_and_install_everest(game_path: String, url: String, on_event: Channel<IpcEvent>) {
     std::thread::spawn(move || {
@@ -5482,6 +5497,21 @@ fn download_and_install_everest(game_path: String, url: String, on_event: Channe
             return;
         }
         let game_path = normalize_game_path_impl(&game_path);
+        // The install replaces the native libraries the running game has loaded,
+        // and MiniInstaller only checks Celeste.exe / Celeste.dll for that, so it
+        // dies halfway through on lib64-win-x64\fmod64.dll and leaves the game
+        // behind in a half-updated state. Refuse early, like the local package
+        // install path does.
+        if is_celeste_running(Path::new(&game_path)) {
+            let error = logged_error(
+                "请先退出 Celeste 再安装 Everest：更新会替换游戏正在使用的 dll（如 lib64-win-x64 里的音频库）。".to_string(),
+            );
+            send_event(
+                &on_event,
+                vec![serde_json::json!("Failed"), serde_json::json!(error)],
+            );
+            return;
+        }
         let result =
             everest::download_and_install_everest(&game_path, &url, &mut |message, progress| {
                 send_event(
@@ -5496,6 +5526,7 @@ fn download_and_install_everest(game_path: String, url: String, on_event: Channe
             ),
             Err(error) => {
                 let error = logged_error(format!("Failed to install Everest: {error:#}"));
+                let error = with_file_in_use_hint(error);
                 send_event(
                     &on_event,
                     vec![serde_json::json!("Failed"), serde_json::json!(error)],