script: Handle null contexts better during JS runtime shutdown. (#34769)

* script: Handle null contexts better during JS runtime shutdown.

Signed-off-by: Josh Matthews <josh@joshmatthews.net>

* lock file

Signed-off-by: sagudev <16504129+sagudev@users.noreply.github.com>

---------

Signed-off-by: Josh Matthews <josh@joshmatthews.net>
Signed-off-by: sagudev <16504129+sagudev@users.noreply.github.com>
Co-authored-by: sagudev <16504129+sagudev@users.noreply.github.com>

components/script/dom/bindings/callback.rs

@@ -93,8 +93,9 @@ impl Drop for CallbackObject {
     #[allow(unsafe_code)]
     fn drop(&mut self) {
         unsafe {
-            let cx = Runtime::get();
-            RemoveRawValueRoot(cx, self.permanent_js_root.get_unsafe());
+            if let Some(cx) = Runtime::get() {
+                RemoveRawValueRoot(cx.as_ptr(), self.permanent_js_root.get_unsafe());
+            }
         }
     }
 }

components/script/dom/bindings/principals.rs

@@ -70,7 +70,9 @@ impl Clone for ServoJSPrincipals {
 impl Drop for ServoJSPrincipals {
     #[inline]
     fn drop(&mut self) {
-        unsafe { JS_DropPrincipals(Runtime::get(), self.as_raw()) };
+        if let Some(cx) = Runtime::get() {
+            unsafe { JS_DropPrincipals(cx.as_ptr(), self.as_raw()) };
+        }
     }
 }
 

components/script/dom/bindings/settings_stack.rs

@@ -117,9 +117,9 @@ impl AutoIncumbentScript {
     pub fn new(global: &GlobalScope) -> Self {
         // Step 2-3.
         unsafe {
-            let cx = Runtime::get();
-            assert!(!cx.is_null());
-            HideScriptedCaller(cx);
+            let cx =
+                Runtime::get().expect("Creating a new incumbent script after runtime shutdown");
+            HideScriptedCaller(cx.as_ptr());
         }
         STACK.with(|stack| {
             trace!("Prepare to run a callback with {:p}", global);
@@ -156,9 +156,9 @@ impl Drop for AutoIncumbentScript {
         });
         unsafe {
             // Step 1-2.
-            let cx = Runtime::get();
-            assert!(!cx.is_null());
-            UnhideScriptedCaller(cx);
+            if let Some(cx) = Runtime::get() {
+                UnhideScriptedCaller(cx.as_ptr());
+            }
         }
     }
 }
@@ -174,9 +174,12 @@ pub fn incumbent_global() -> Option<DomRoot<GlobalScope>> {
     // there's nothing on the JS stack, which will cause us to check the
     // incumbent script stack below.
     unsafe {
-        let cx = Runtime::get();
-        assert!(!cx.is_null());
-        let global = GetScriptedCallerGlobal(cx);
+        let Some(cx) = Runtime::get() else {
+            // It's not meaningful to return a global object if the runtime
+            // no longer exists.
+            return None;
+        };
+        let global = GetScriptedCallerGlobal(cx.as_ptr());
         if !global.is_null() {
             return Some(GlobalScope::from_object(global));
         }

components/script/dom/globalscope.rs

@@ -2253,7 +2253,10 @@ impl GlobalScope {
 
     #[allow(unsafe_code)]
     pub fn get_cx() -> SafeJSContext {
-        unsafe { SafeJSContext::from_ptr(Runtime::get()) }
+        let cx = Runtime::get()
+            .expect("Can't obtain context after runtime shutdown")
+            .as_ptr();
+        unsafe { SafeJSContext::from_ptr(cx) }
     }
 
     pub fn crypto(&self) -> DomRoot<Crypto> {
@@ -3058,14 +3061,13 @@ impl GlobalScope {
     /// ["current"]: https://html.spec.whatwg.org/multipage/#current
     #[allow(unsafe_code)]
     pub fn current() -> Option<DomRoot<Self>> {
+        let cx = Runtime::get()?;
         unsafe {
-            let cx = Runtime::get();
-            assert!(!cx.is_null());
-            let global = CurrentGlobalOrNull(cx);
+            let global = CurrentGlobalOrNull(cx.as_ptr());
             if global.is_null() {
                 None
             } else {
-                Some(global_scope_from_global(global, cx))
+                Some(global_scope_from_global(global, cx.as_ptr()))
             }
         }
     }

components/script/dom/promise.rs

@@ -78,9 +78,9 @@ impl Drop for Promise {
         unsafe {
             let object = self.permanent_js_root.get().to_object();
             assert!(!object.is_null());
-            let cx = Runtime::get();
-            assert!(!cx.is_null());
-            RemoveRawValueRoot(cx, self.permanent_js_root.get_unsafe());
+            if let Some(cx) = Runtime::get() {
+                RemoveRawValueRoot(cx.as_ptr(), self.permanent_js_root.get_unsafe());
+            }
         }
     }
 }

components/script/script_runtime.rs

@@ -621,7 +621,9 @@ impl Runtime {
                 &*(closure as *mut NetworkingTaskSource);
             let runnable = Runnable(dispatchable);
             let task = task!(dispatch_to_event_loop_message: move || {
-                runnable.run(RustRuntime::get(), Dispatchable_MaybeShuttingDown::NotShuttingDown);
+                if let Some(cx) = RustRuntime::get() {
+                    runnable.run(cx.as_ptr(), Dispatchable_MaybeShuttingDown::NotShuttingDown);
+                }
             });
 
             networking_task_src.queue_unconditionally(task).is_ok()
@@ -801,6 +803,8 @@ impl Runtime {
 impl Drop for Runtime {
     #[allow(unsafe_code)]
     fn drop(&mut self) {
+        self.microtask_queue.clear();
+
         unsafe {
             DeleteJobQueue(self.job_queue);
         }