Engine: Keep <Fragment> fallbacks in the tree while other visitors run

lib/herb/engine/slots/visitor.rb

@@ -206,6 +206,7 @@ def initialize(markers: Markers.new, mode: :server, identifier: :path, mark: tru
 
           @fragment_nodes = fragment_nodes.compare_by_identity
           @fragment_fallbacks = fragment_fallbacks.compare_by_identity
+          @exposed_fallbacks = [] #: Array[untyped]
           @deferred_nodes = deferred_nodes.compare_by_identity
           @assignment_nodes = assignment_nodes.compare_by_identity
         end
@@ -661,6 +662,7 @@ def visit_document_node(node)
           @states.apply_states
 
           wrap_bound_renders
+          expose_fallbacks(node)
         end
 
         #: () -> Hash[String, String]?
@@ -670,6 +672,7 @@ def statics
 
         #: (untyped) -> void
         def finish(node)
+          withdraw_fallbacks(node)
           follow_replacements
 
           return unless @mark
@@ -1982,6 +1985,29 @@ def append_statics(document_node)
           document_node.children.concat(nodes)
         end
 
+        #: (Herb::AST::DocumentNode) -> void
+        def expose_fallbacks(document_node)
+          return if @fragment_fallbacks.empty?
+
+          @exposed_fallbacks = @fragment_fallbacks.each_value.flat_map { |body| body } #: Array[untyped]
+
+          document_node.children.concat(@exposed_fallbacks)
+
+          nil
+        end
+
+        #: (Herb::AST::DocumentNode) -> void
+        def withdraw_fallbacks(document_node)
+          exposed = @exposed_fallbacks
+
+          return if exposed.empty?
+
+          document_node.children.reject! { |child| exposed.any? { |node| node.equal?(child) } }
+          @exposed_fallbacks = [] #: Array[untyped]
+
+          nil
+        end
+
         #: () -> Array[[String, Array[untyped]]]
         def fallback_statics_entries
           @fragment_fallbacks.filter_map { |node, body|

test/engine/scoped_style/visitor_test.rb

@@ -394,5 +394,14 @@ def hoisted(source, filename: TEMPLATE)
       refute_nil diagnostic
       assert_equal "app/views/posts/_dynamic.html.erb", diagnostic.template
     end
+
+    test "carries the scope into the fallback a client stands in while content is stale" do
+      source = %(<%# herb:slots client %><%# herb:state (album: "") %><style scoped>.g { color: red; }</style><Fragment on="album"><b>Loaded</b><Fallback><i class="g">Loading</i></Fallback></Fragment>)
+
+      assert_compiled_snapshot(
+        source,
+        options(visitors: [Herb::Engine::Slots::Visitor.new(mode: :client)], project_path: PROJECT_PATH)
+      )
+    end
   end
 end