Replace HTMLCollection postAttach's with indexed/named getter

This solves two issues. First, it's more correct, the indexers should be live.
Second, it makes sure that anything with an HTMLCollection prototype, like
HTMLOptionsCollection, also gets access to the index getters.

We could solve the 2nd issue by making `postAttach` work up the prototype
chain, but since postAttach is wrong (not live), I prefer this solution.

src/browser/dom/html_collection.zig

@@ -429,24 +429,23 @@ pub const HTMLCollection = struct {
         return null;
     }
 
-    pub fn postAttach(self: *HTMLCollection, js_this: JsThis) !void {
-        const len = try self.get_length();
-        for (0..len) |i| {
-            const node = try self.item(@intCast(i)) orelse unreachable;
-            const e = @as(*parser.Element, @ptrCast(node));
-            const as_interface = try Element.toInterface(e);
-            try js_this.setIndex(@intCast(i), as_interface, .{});
+    pub fn indexed_get(self: *HTMLCollection, index: u32, has_value: *bool) !?Union {
+        return (try _item(self, index)) orelse {
+            has_value.* = false;
+            return undefined;
+        };
+    }
 
-            if (try item_name(e)) |name| {
+    pub fn named_get(self: *const HTMLCollection, name: []const u8, has_value: *bool) !?Union {
         // Even though an entry might have an empty id, the spec says
         // that namedItem("") should always return null
-                if (name.len > 0) {
-                    // Named fields should not be enumerable (it is defined with
-                    // the LegacyUnenumerableNamedProperties flag.)
-                    try js_this.set(name, as_interface, .{ .DONT_ENUM = true });
-                }
-            }
+        if (name.len == 0) {
+            return null;
         }
+        return (try _namedItem(self, name)) orelse {
+            has_value.* = false;
+            return undefined;
+        };
     }
 };
 

src/tests/html/select.html

@@ -55,6 +55,7 @@
   o3.value = 'o3';
   options.add(o3)
   testing.expectEqual(3, options.length);
+  testing.expectEqual('o3', options[2].value);
   testing.expectEqual('o3', options.item(2).value);
 
   let o4 = document.createElement('option');
@@ -71,5 +72,9 @@
 
   options.remove(3)
   testing.expectEqual(4, options.length);
+  testing.expectEqual('o3', options[3].value);
   testing.expectEqual('o3', options.item(3).value);
+
+  testing.expectEqual(undefined, options[10]);
+  testing.expectEqual(null, options.item(10));
 </script>