fix(macos): Prevent NSExceptions when dropping a webview with registered protocols

.changes/macos-drop-panic.md

@@ -0,0 +1,5 @@
+---
+"wry": patch
+---
+
+On macOS, prevent NSExceptions and invalid memory access panics when dropping the WebView while custom protocols handlers may still be running.

src/wkwebview/mod.rs

@@ -18,6 +18,7 @@ use cocoa::{
   foundation::{NSDictionary, NSFastEnumeration, NSInteger},
 };
 use dpi::{LogicalPosition, LogicalSize};
+use once_cell::sync::Lazy;
 use raw_window_handle::{HasWindowHandle, RawWindowHandle};
 
 use std::{
@@ -71,6 +72,8 @@ const ACCEPT_FIRST_MOUSE: &str = "accept_first_mouse";
 
 const NS_JSON_WRITING_FRAGMENTS_ALLOWED: u64 = 4;
 
+static WEBVIEW_IDS: Lazy<Mutex<Vec<usize>>> = Lazy::new(Default::default);
+
 pub(crate) struct InnerWebView {
   pub webview: id,
   pub manager: id,
@@ -86,6 +89,7 @@ pub(crate) struct InnerWebView {
   drag_drop_ptr: *mut Box<dyn Fn(crate::DragDropEvent) -> bool>,
   download_delegate: id,
   protocol_ptrs: Vec<*mut Box<dyn Fn(Request<Vec<u8>>, RequestAsyncResponder)>>,
+  webview_id: usize,
 }
 
 impl InnerWebView {
@@ -172,6 +176,8 @@ impl InnerWebView {
         #[cfg(feature = "tracing")]
         let span = tracing::info_span!("wry::custom_protocol::handle", uri = tracing::field::Empty)
           .entered();
+        let webview_id = *this.get_ivar::<usize>("webview_id");
+
         let function = this.get_ivar::<*mut c_void>("function");
         if !function.is_null() {
           let function =
@@ -271,14 +277,25 @@ impl InnerWebView {
 
                   let urlresponse: id = msg_send![class!(NSHTTPURLResponse), alloc];
                   let response: id = msg_send![urlresponse, initWithURL:url statusCode: wanted_status_code HTTPVersion:NSString::new(&wanted_version) headerFields:headers];
+                  if !WEBVIEW_IDS.lock().unwrap().contains(&webview_id) {
+                    return;
+                  }
                   let () = msg_send![task, didReceiveResponse: response];
 
                   // Send data
                   let bytes = content.as_ptr() as *mut c_void;
                   let data: id = msg_send![class!(NSData), alloc];
                   let data: id = msg_send![data, initWithBytesNoCopy:bytes length:content.len() freeWhenDone: if content.len() == 0 { NO } else { YES }];
+
+                  if !WEBVIEW_IDS.lock().unwrap().contains(&webview_id) {
+                    return;
+                  }
                   let () = msg_send![task, didReceiveData: data];
+
                   // Finish
+                  if !WEBVIEW_IDS.lock().unwrap().contains(&webview_id) {
+                    return;
+                  }
                   let () = msg_send![task, didFinish];
                 },
               );
@@ -299,6 +316,11 @@ impl InnerWebView {
     }
     extern "C" fn stop_task(_: &Object, _: Sel, _webview: id, _task: id) {}
 
+    let mut wv_ids = WEBVIEW_IDS.lock().unwrap();
+    let webview_id = wv_ids.last().unwrap_or(&0) + 1;
+    wv_ids.push(webview_id);
+    drop(wv_ids);
+
     // Safety: objc runtime calls are unsafe
     unsafe {
       // Config and custom protocol
@@ -318,6 +340,7 @@ impl InnerWebView {
         let cls = match cls {
           Some(mut cls) => {
             cls.add_ivar::<*mut c_void>("function");
+            cls.add_ivar::<usize>("webview_id");
             cls.add_method(
               sel!(webView:startURLSchemeTask:),
               start_task as extern "C" fn(&Object, Sel, id, id),
@@ -335,6 +358,7 @@ impl InnerWebView {
         protocol_ptrs.push(function);
 
         (*handler).set_ivar("function", function as *mut _ as *mut c_void);
+        (*handler).set_ivar("webview_id", webview_id);
         let () = msg_send![config, setURLSchemeHandler:handler forURLScheme:NSString::new(&name)];
       }
 
@@ -878,6 +902,7 @@ impl InnerWebView {
         download_delegate,
         protocol_ptrs,
         is_child,
+        webview_id,
       };
 
       // Initialize scripts
@@ -1245,6 +1270,11 @@ pub fn platform_webview_version() -> Result<String> {
 
 impl Drop for InnerWebView {
   fn drop(&mut self) {
+    WEBVIEW_IDS
+      .lock()
+      .unwrap()
+      .retain(|i| i != &self.webview_id);
+
     // We need to drop handler closures here
     unsafe {
       if !self.ipc_handler_ptr.is_null() {