env: Force a separate Firefox profile

Otherwise Firefox launched in the guest will concurrently access the
host profile, corrupting it. We can make it not do that by implementing
locks, which would fix the corruption but would still break the browser
in the guest. So let's explicitly set a muvm-private Firefox profile.

Signed-off-by: Asahi Lina <lina@asahilina.net>

Author: asahilina

crates/muvm/src/env.rs

@@ -90,6 +90,27 @@ pub fn prepare_env_vars(env: Vec<(String, Option<String>)>) -> Result<HashMap<St
     env_map.insert("GTK_IM_MODULE".to_owned(), "xim".to_owned());
     env_map.insert("QT_IM_MODULE".to_owned(), "xim".to_owned());
 
+    // Force a separate Firefox profile, since Firefox in muvm cannot see
+    // the lock from outside the VM and will concurrently launch on the same
+    // profile, corrupting it. This makes Firefox safely work in the VM
+    // (for browser launches).
+    if let Ok(home) = env::var("HOME") {
+        let mut path = PathBuf::new();
+        path.push(home);
+        path.push(".mozilla");
+        path.push("firefox");
+        if path.exists() {
+            path.push("muvm-profile");
+            if !path.exists() {
+                std::fs::create_dir(&path)?;
+            }
+            env_map.insert(
+                "XRE_PROFILE_PATH".to_owned(),
+                path.to_str().unwrap().to_owned(),
+            );
+        }
+    }
+
     for (key, value) in env {
         let value = value.map_or_else(
             || env::var(&key).with_context(|| format!("Failed to get `{key}` env var")),