Log on lack of Reaction scope in debug

Flag Range.cloneContents as CEReactions

setAttributeNode triggers single reaction, rather than a remove + add.

Author: karlseguin

src/browser/CustomElementReactions.zig

@@ -97,7 +97,7 @@ fn route(self: *Self, frame: *Frame, reaction: Reaction) !void {
         return;
     }
     if (comptime IS_DEBUG) {
-        lp.log.err(.bug, "custom element scope", .{.note = "Missing explicit reaction scope, using fallback. This log is only generated in debug builds."});
+        lp.log.err(.bug, "custom element scope", .{ .note = "Missing explicit reaction scope, using fallback. This log is only generated in debug builds." });
     }
     try self.backup_queue.append(self.allocator, reaction);
     if (!self.backup_scheduled) {

src/browser/webapi/Range.zig

@@ -720,7 +720,7 @@ pub const JsApi = struct {
     pub const cloneRange = bridge.function(Range.cloneRange, .{ .dom_exception = true });
     pub const insertNode = bridge.function(Range.insertNode, .{ .dom_exception = true, .ce_reactions = true });
     pub const deleteContents = bridge.function(Range.deleteContents, .{ .dom_exception = true, .ce_reactions = true });
-    pub const cloneContents = bridge.function(Range.cloneContents, .{ .dom_exception = true });
+    pub const cloneContents = bridge.function(Range.cloneContents, .{ .dom_exception = true, .ce_reactions = true });
     pub const extractContents = bridge.function(Range.extractContents, .{ .dom_exception = true, .ce_reactions = true });
     pub const surroundContents = bridge.function(Range.surroundContents, .{ .dom_exception = true, .ce_reactions = true });
     pub const createContextualFragment = bridge.function(Range.createContextualFragment, .{ .dom_exception = true, .ce_reactions = true });

src/browser/webapi/element/Attribute.zig

@@ -255,7 +255,11 @@ pub const List = struct {
 
         const existing_attribute = try self.getAttribute(attribute._name, element, frame);
         if (existing_attribute) |ea| {
-            try self.delete(ea._name, element, frame);
+            // Per DOM "replace an attribute": one handle-attribute-changes call
+            // with (old, new), not a remove-then-add that would fire two
+            // attributeChanged reactions. Detach the old wrapper; put() updates
+            // the entry in place and fires the single reaction.
+            ea._element = null;
         }
 
         const entry = try self.put(attribute._name, attribute._value, element, frame);