fix(node): drop cached node id when the document is updated

CHANGELOG.md

@@ -12,6 +12,9 @@
 ### Fixed
 - Headers can be added on a remote browser whose `/json/version` has no `User-Agent`, such as browserless v2, instead of
   failing with `Invalid parameters` [rubycdp/cuprite#300]
+- A `Ferrum::Node` found before a navigation or reload kept its cached CDP node id, which Chrome reuses for the new
+  document, so `focus`, `click`, `scroll_into_view` and friends silently hit another element. Node ids are now dropped
+  on `DOM.documentUpdated` and such nodes raise `Ferrum::NodeNotFoundError` [#86]
 
 ### Removed
 - `Browser::Process#default_user_agent`, `#browser_version`, `#protocol_version`, `#v8_version` and `#webkit_version`,

lib/ferrum/node.rb

@@ -23,20 +23,26 @@ def initialize(frame, target_id, description, object_id: nil, node_id: nil)
       @tag_name = description["nodeName"].downcase
       @object_id = object_id
       @node_id = node_id
+      @document_version = @page.document_version
     end
 
     # Frontend node id is resolved lazily, on first actual need (focus, click, scroll_into_view, etc.)
     # We can try to subscribe to `DOM.childNodeRemoved` and `DOM.childNodeInserted` in the future
     # to keep track of nodes.
     def node_id
-      @node_id ||= begin
+      return @node_id if @node_id && @document_version == page.document_version
+
+      document_version = page.document_version
+      @node_id = begin
         id = page.command("DOM.requestNode", objectId: @object_id)["nodeId"]
-        raise NodeNotFoundError, "node is not trackable" if id.zero?
+        raise NodeNotFoundError, { "message" => "node is not trackable" } if id.zero?
 
         id
       rescue NoExecutionContextError
-        raise NodeNotFoundError, "node is not trackable"
+        raise NodeNotFoundError, { "message" => "node is not trackable" }
       end
+      @document_version = document_version
+      @node_id
     end
 
     # Whether this is an element node, as opposed to e.g. a text node.

lib/ferrum/page.rb

@@ -87,6 +87,12 @@ class Page
     # @return [Downloads]
     attr_reader :downloads
 
+    # Bumped every time Chrome reports `DOM.documentUpdated`, which
+    # invalidates every node id handed out before it.
+    #
+    # @return [Integer]
+    attr_reader :document_version
+
     def initialize(client, context_id:, target_id:, proxy: nil)
       @client = client
       @context_id = context_id
@@ -96,6 +102,7 @@ def initialize(client, context_id:, target_id:, proxy: nil)
       @frames = Concurrent::Map.new
       @main_frame = Frame.new(nil, self)
       @event = Utils::Event.new.tap(&:set)
+      @document_version = 0
       self.proxy = proxy
 
       @mouse = Mouse.new(self)
@@ -526,6 +533,8 @@ def subscribe
       network.subscribe
       downloads.subscribe
 
+      on("DOM.documentUpdated") { @document_version += 1 }
+
       if @options.logger
         on("Runtime.consoleAPICalled") do |params|
           log_console_api(params)

sig/ferrum/node.rbs

@@ -6,6 +6,7 @@ module Ferrum
 
     @node_id: untyped
     @object_id: untyped
+    @document_version: ::Integer
 
     attr_reader page: untyped
 

sig/ferrum/page.rbs

@@ -23,6 +23,7 @@ module Ferrum
     attr_reader headers: Headers
     attr_reader cookies: Cookies
     attr_reader downloads: Downloads
+    attr_reader document_version: ::Integer
     attr_reader client: (Client | SessionClient)
 
     @client: (Client | SessionClient)
@@ -40,6 +41,7 @@ module Ferrum
     @tracing: Page::Tracing
     @downloads: Downloads
     @referrer: String?
+    @document_version: ::Integer
 
     def initialize: ((Client | SessionClient) client, context_id: String?, target_id: String, ?proxy: { host: String, port: ::Integer, user: String?, password: String? }?) -> void
 

spec/node_spec.rb

@@ -47,6 +47,20 @@
       expect { node.text }.to raise_error(Ferrum::NodeNotFoundError)
     end
 
+    it "raises an error instead of focusing a node from the new document after reload" do
+      browser.go_to("/form")
+      node = browser.at_css("#customer_email")
+      node.focus
+
+      browser.refresh
+      browser.at_css("#customer_email").focus
+      browser.at_css("#customer_email").blur
+
+      expect { node.focus }.to raise_error(Ferrum::NodeNotFoundError, "node is not trackable")
+      expect { node.focus }.to raise_error(Ferrum::NodeNotFoundError, "node is not trackable")
+      expect(browser.evaluate("document.activeElement.id")).not_to eq("customer_email")
+    end
+
     it "raises an error if the element is not visible" do
       browser.go_to("/index")