Implement XMLHttpRequest.upload

Return an XMLHttpRequestUpload (inheriting XMLHttpRequestEventTarget) from
the lazily-cached `upload` attribute. Fixes htmx login flows that called
`xhr.upload.addEventListener(...)`.

src/browser/js/bridge.zig

@@ -949,6 +949,7 @@ pub const PageJsApis = flattenTypes(&.{
     @import("../webapi/net/URLSearchParams.zig"),
     @import("../webapi/net/XMLHttpRequest.zig"),
     @import("../webapi/net/XMLHttpRequestEventTarget.zig"),
+    @import("../webapi/net/XMLHttpRequestUpload.zig"),
     @import("../webapi/net/WebSocket.zig"),
     @import("../webapi/event/CloseEvent.zig"),
     @import("../webapi/streams/ReadableStream.zig"),
@@ -1036,6 +1037,7 @@ pub const WorkerJsApis = flattenTypes(&.{
     @import("../webapi/canvas/OffscreenCanvasRenderingContext2D.zig"),
     @import("../webapi/net/XMLHttpRequest.zig"),
     @import("../webapi/net/XMLHttpRequestEventTarget.zig"),
+    @import("../webapi/net/XMLHttpRequestUpload.zig"),
     @import("../webapi/net/WebSocket.zig"),
     @import("../webapi/FileReader.zig"),
     @import("../webapi/ImageData.zig"),

src/browser/tests/net/xhr.html

@@ -329,3 +329,22 @@
     });
   }
 </script>
+
+<script id=xhr_upload type=module>
+  {
+    // upload is an XMLHttpRequestUpload (an XMLHttpRequestEventTarget) and
+    // exposes addEventListener; htmx relies on this not throwing.
+    const req = new XMLHttpRequest();
+    testing.expectEqual('XMLHttpRequestUpload', req.upload.constructor.name);
+    testing.expectEqual(true, req.upload instanceof XMLHttpRequestEventTarget);
+    testing.expectEqual(true, req.upload instanceof EventTarget);
+    testing.expectEqual('function', typeof req.upload.addEventListener);
+
+    // The same instance is returned on every access so listeners stick.
+    testing.expectEqual(req.upload, req.upload);
+
+    let registered = false;
+    req.upload.addEventListener('progress', () => { registered = true; });
+    testing.expectEqual(false, registered);
+  }
+</script>

src/browser/webapi/net/XMLHttpRequest.zig

@@ -34,6 +34,7 @@ const EventTarget = @import("../EventTarget.zig");
 const Headers = @import("Headers.zig");
 const BodyInit = @import("body_init.zig").BodyInit;
 const XMLHttpRequestEventTarget = @import("XMLHttpRequestEventTarget.zig");
+const XMLHttpRequestUpload = @import("XMLHttpRequestUpload.zig");
 
 const log = lp.log;
 const Execution = js.Execution;
@@ -44,6 +45,7 @@ const XMLHttpRequest = @This();
 _rc: lp.RC(u8) = .{},
 _exec: *const Execution,
 _proto: *XMLHttpRequestEventTarget,
+_upload: ?*XMLHttpRequestUpload = null,
 _arena: Allocator,
 _http_response: ?HttpClient.Response = null,
 _active_request: bool = false,
@@ -112,29 +114,9 @@ pub fn deinit(self: *XMLHttpRequest, page: *Page) void {
         func.release();
     }
 
-    {
-        const proto = self._proto;
-        if (proto._on_abort) |func| {
-            func.release();
-        }
-        if (proto._on_error) |func| {
-            func.release();
-        }
-        if (proto._on_load) |func| {
-            func.release();
-        }
-        if (proto._on_load_end) |func| {
-            func.release();
-        }
-        if (proto._on_load_start) |func| {
-            func.release();
-        }
-        if (proto._on_progress) |func| {
-            func.release();
-        }
-        if (proto._on_timeout) |func| {
-            func.release();
-        }
+    self._proto.releaseListeners();
+    if (self._upload) |upload| {
+        upload._proto.releaseListeners();
     }
 
     page.releaseArena(self._arena);
@@ -289,6 +271,18 @@ pub fn send(self: *XMLHttpRequest, body_: ?BodyInit, exec_: *const Execution) !v
     };
 }
 
+// https://xhr.spec.whatwg.org/#the-upload-attribute
+// The XMLHttpRequestUpload object is created lazily and cached: scripts expect
+// the same instance on every access so their event listeners stick.
+pub fn getUpload(self: *XMLHttpRequest) !*XMLHttpRequestUpload {
+    if (self._upload) |upload| {
+        return upload;
+    }
+    const upload = try self._exec._factory.xhrEventTarget(self._arena, XMLHttpRequestUpload{ ._proto = undefined });
+    self._upload = upload;
+    return upload;
+}
+
 pub fn getReadyState(self: *const XMLHttpRequest) u32 {
     return @intFromEnum(self._ready_state);
 }
@@ -611,6 +605,7 @@ pub const JsApi = struct {
     pub const DONE = bridge.property(@intFromEnum(XMLHttpRequest.ReadyState.done), .{ .template = true });
 
     pub const onreadystatechange = bridge.accessor(XMLHttpRequest.getOnReadyStateChange, XMLHttpRequest.setOnReadyStateChange, .{});
+    pub const upload = bridge.accessor(XMLHttpRequest.getUpload, null, .{});
     pub const timeout = bridge.accessor(XMLHttpRequest.getTimeout, XMLHttpRequest.setTimeout, .{});
     pub const withCredentials = bridge.accessor(XMLHttpRequest.getWithCredentials, XMLHttpRequest.setWithCredentials, .{ .dom_exception = true });
     pub const open = bridge.function(XMLHttpRequest.open, .{});

src/browser/webapi/net/XMLHttpRequestEventTarget.zig

@@ -37,13 +37,24 @@ _on_timeout: ?js.Function.Temp = null,
 
 pub const Type = union(enum) {
     request: *@import("XMLHttpRequest.zig"),
-    // TODO: xml_http_request_upload
+    upload: *@import("XMLHttpRequestUpload.zig"),
 };
 
 pub fn asEventTarget(self: *XMLHttpRequestEventTarget) *EventTarget {
     return self._proto;
 }
 
+pub fn releaseListeners(self: *XMLHttpRequestEventTarget) void {
+    inline for (.{
+        "_on_abort",      "_on_error",    "_on_load",    "_on_load_end",
+        "_on_load_start", "_on_progress", "_on_timeout",
+    }) |field| {
+        if (@field(self, field)) |func| {
+            func.release();
+        }
+    }
+}
+
 pub fn dispatch(self: *XMLHttpRequestEventTarget, comptime event_type: DispatchType, progress_: ?Progress, exec: *const Execution) !void {
     const field, const typ = comptime blk: {
         break :blk switch (event_type) {

src/browser/webapi/net/XMLHttpRequestUpload.zig

@@ -0,0 +1,46 @@
+// Copyright (C) 2023-2026  Lightpanda (Selecy SAS)
+//
+// Francis Bouvier <francis@lightpanda.io>
+// Pierre Tachoire <pierre@lightpanda.io>
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as
+// published by the Free Software Foundation, either version 3 of the
+// License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+const js = @import("../../js/js.zig");
+
+const EventTarget = @import("../EventTarget.zig");
+const XMLHttpRequestEventTarget = @import("XMLHttpRequestEventTarget.zig");
+
+// https://xhr.spec.whatwg.org/#xmlhttprequestupload
+//
+// Returned by XMLHttpRequest.upload. It only inherits from
+// XMLHttpRequestEventTarget; it has no members of its own. We don't yet emit
+// upload progress events, but the object still needs to exist so scripts (e.g.
+// htmx) can call addEventListener on it without throwing.
+const XMLHttpRequestUpload = @This();
+
+_proto: *XMLHttpRequestEventTarget,
+
+pub fn asEventTarget(self: *XMLHttpRequestUpload) *EventTarget {
+    return self._proto.asEventTarget();
+}
+
+pub const JsApi = struct {
+    pub const bridge = js.Bridge(XMLHttpRequestUpload);
+
+    pub const Meta = struct {
+        pub const name = "XMLHttpRequestUpload";
+        pub const prototype_chain = bridge.prototypeChain();
+        pub var class_id: bridge.ClassId = undefined;
+    };
+};