document.applets should always return an empty collection

Add a new .empty mode to HTMLCollection.

Fixes WPT /shadow-dom/leaktests/html-collection.html

src/browser/tests/legacy/html/document.html

@@ -6,6 +6,7 @@
 </html>
 
 <script src="../testing.js"></script>
+<applet></applet>
 
 <script id=document>
   testing.expectEqual('HTMLDocument', document.__proto__.constructor.name);
@@ -23,7 +24,7 @@
   testing.expectEqual(2, document.scripts.length);
   testing.expectEqual(0, document.forms.length);
   testing.expectEqual(1, document.links.length);
-  testing.expectEqual(0, document.applets.length);
+  testing.expectEqual(0, document.applets.length); // deprecated, always returns 0
   testing.expectEqual(0, document.anchors.length);
   testing.expectEqual(7, document.all.length);
   testing.expectEqual('document', document.currentScript.id);

src/browser/webapi/HTMLDocument.zig

@@ -167,9 +167,8 @@ pub fn getEmbeds(self: *HTMLDocument, page: *Page) !collections.NodeLive(.tag) {
     return collections.NodeLive(.tag).init(self.asNode(), .embed, page);
 }
 
-const applet_string = String.init(undefined, "applet", .{}) catch unreachable;
-pub fn getApplets(self: *HTMLDocument, page: *Page) !collections.NodeLive(.tag_name) {
-    return collections.NodeLive(.tag_name).init(self.asNode(), applet_string, page);
+pub fn getApplets(_: *const HTMLDocument) collections.HTMLCollection {
+    return .{ ._data = .empty };
 }
 
 pub fn getCurrentScript(self: *const HTMLDocument) ?*Element.Html.Script {

src/browser/webapi/collections.zig

@@ -20,14 +20,15 @@ pub const NodeLive = @import("collections/node_live.zig").NodeLive;
 pub const ChildNodes = @import("collections/ChildNodes.zig");
 pub const DOMTokenList = @import("collections/DOMTokenList.zig");
 pub const RadioNodeList = @import("collections/RadioNodeList.zig");
+pub const HTMLCollection = @import("collections/HTMLCollection.zig");
 pub const HTMLAllCollection = @import("collections/HTMLAllCollection.zig");
 pub const HTMLOptionsCollection = @import("collections/HTMLOptionsCollection.zig");
 pub const HTMLFormControlsCollection = @import("collections/HTMLFormControlsCollection.zig");
 
 pub fn registerTypes() []const type {
     return &.{
-        @import("collections/HTMLCollection.zig"),
-        @import("collections/HTMLCollection.zig").Iterator,
+        HTMLCollection,
+        HTMLCollection.Iterator,
         @import("collections/NodeList.zig"),
         @import("collections/NodeList.zig").KeyIterator,
         @import("collections/NodeList.zig").ValueIterator,

src/browser/webapi/collections/HTMLCollection.zig

@@ -36,6 +36,7 @@ const Mode = enum {
     links,
     anchors,
     form,
+    empty,
 };
 
 const HTMLCollection = @This();
@@ -52,22 +53,26 @@ _data: union(Mode) {
     links: NodeLive(.links),
     anchors: NodeLive(.anchors),
     form: NodeLive(.form),
+    empty: void,
 },
 
 pub fn length(self: *HTMLCollection, page: *const Page) u32 {
     return switch (self._data) {
+        .empty => 0,
         inline else => |*impl| impl.length(page),
     };
 }
 
 pub fn getAtIndex(self: *HTMLCollection, index: usize, page: *const Page) ?*Element {
     return switch (self._data) {
+        .empty => null,
         inline else => |*impl| impl.getAtIndex(index, page),
     };
 }
 
 pub fn getByName(self: *HTMLCollection, name: []const u8, page: *Page) ?*Element {
     return switch (self._data) {
+        .empty => null,
         inline else => |*impl| impl.getByName(name, page),
     };
 }
@@ -87,6 +92,7 @@ pub fn iterator(self: *HTMLCollection, page: *Page) !*Iterator {
             .links => |*impl| .{ .links = impl._tw.clone() },
             .anchors => |*impl| .{ .anchors = impl._tw.clone() },
             .form => |*impl| .{ .form = impl._tw.clone() },
+            .empty => .empty,
         },
     }, page);
 }
@@ -106,6 +112,7 @@ pub const Iterator = GenericIterator(struct {
         links: TreeWalker.FullExcludeSelf,
         anchors: TreeWalker.FullExcludeSelf,
         form: TreeWalker.FullExcludeSelf,
+        empty: void,
     },
 
     pub fn next(self: *@This(), _: *Page) ?*Element {
@@ -121,6 +128,7 @@ pub const Iterator = GenericIterator(struct {
             .links => |*impl| impl.nextTw(&self.tw.links),
             .anchors => |*impl| impl.nextTw(&self.tw.anchors),
             .form => |*impl| impl.nextTw(&self.tw.form),
+            .empty => return null,
         };
     }
 }, null);