Add finalizer mode

When a type is finalized by V8, it's because it's fallen out of scope. When a
type is finalized by Zig, it's because the Context is being shutdown.

Those are two different environments and might require distinct cleanup logic.
Specifically, a zig-initiated finalization needs to consider that the page and
context are being shutdown. It isn't necessarily safe to execute JavaScript at
this point, and thus, not safe to execute a callback (on_error, on_abort,
ready_state_change, ...).

src/browser/js/bridge.zig

@@ -92,11 +92,11 @@ pub fn Builder(comptime T: type) type {
             return entries;
         }
 
-        pub fn finalizer(comptime func: *const fn (self: *T) void) Finalizer {
+        pub fn finalizer(comptime func: *const fn (self: *T, comptime shutdown: bool) void) Finalizer {
             return .{
                 .from_zig = struct {
                     fn wrap(ptr: *anyopaque) void {
-                        func(@ptrCast(@alignCast(ptr)));
+                        func(@ptrCast(@alignCast(ptr)), true);
                     }
                 }.wrap,
 
@@ -115,7 +115,7 @@ pub fn Builder(comptime T: type) type {
                         if (!ctx.identity_map.contains(@intFromPtr(ptr))) {
                             return;
                         }
-                        func(self);
+                        func(self, false);
                         ctx.release(ptr);
                     }
                 }.wrap,

src/browser/webapi/net/XMLHttpRequest.zig

@@ -90,9 +90,13 @@ pub fn init(page: *Page) !*XMLHttpRequest {
     });
 }
 
-pub fn deinit(self: *XMLHttpRequest) void {
+pub fn deinit(self: *XMLHttpRequest, comptime shutdown: bool) void {
     if (self._transfer) |transfer| {
+        if (shutdown) {
             transfer.terminate();
+        } else {
+            transfer.abort(error.Abort);
+        }
         self._transfer = null;
     }
     self._page.releaseArena(self._arena);

src/http/Client.zig

@@ -371,7 +371,7 @@ fn makeTransfer(self: *Client, req: Request) !*Transfer {
     return transfer;
 }
 
-fn requestFailed(self: *Client, transfer: *Transfer, err: anyerror) void {
+fn requestFailed(self: *Client, transfer: *Transfer, err: anyerror, comptime execute_callback: bool) void {
     // this shouldn't happen, we'll crash in debug mode. But in release, we'll
     // just noop this state.
     if (comptime IS_DEBUG) {
@@ -390,7 +390,9 @@ fn requestFailed(self: *Client, transfer: *Transfer, err: anyerror) void {
         });
     }
 
+    if (execute_callback) {
         transfer.req.error_callback(transfer.ctx, err);
+    }
 }
 
 // Restrictive since it'll only work if there are no inflight requests. In some
@@ -600,7 +602,7 @@ fn processMessages(self: *Client) !bool {
             if (!transfer._header_done_called) {
                 const proceed = transfer.headerDoneCallback(easy) catch |err| {
                     log.err(.http, "header_done_callback", .{ .err = err });
-                    self.requestFailed(transfer, err);
+                    self.requestFailed(transfer, err, true);
                     continue;
                 };
                 if (!proceed) {
@@ -611,7 +613,7 @@ fn processMessages(self: *Client) !bool {
             transfer.req.done_callback(transfer.ctx) catch |err| {
                 // transfer isn't valid at this point, don't use it.
                 log.err(.http, "done_callback", .{ .err = err });
-                self.requestFailed(transfer, err);
+                self.requestFailed(transfer, err, true);
                 continue;
             };
 
@@ -622,7 +624,7 @@ fn processMessages(self: *Client) !bool {
             }
             processed = true;
         } else |err| {
-            self.requestFailed(transfer, err);
+            self.requestFailed(transfer, err, true);
         }
     }
     return processed;
@@ -972,7 +974,7 @@ pub const Transfer = struct {
     }
 
     pub fn abort(self: *Transfer, err: anyerror) void {
-        self.client.requestFailed(self, err);
+        self.client.requestFailed(self, err, true);
         if (self._handle != null) {
             self.client.endTransfer(self);
         }
@@ -980,6 +982,7 @@ pub const Transfer = struct {
     }
 
     pub fn terminate(self: *Transfer) void {
+        self.client.requestFailed(self, error.Shutdown, false);
         if (self._handle != null) {
             self.client.endTransfer(self);
         }