fix(client): release in-flight commands when the connection dies

CHANGELOG.md

@@ -23,6 +23,9 @@
   the browser; a failed `IO.close` is raised to the caller.
 
 ### Fixed
+- Commands in flight when the browser died waited out `:protocol_timeout` each before raising, so a dead browser
+  turned into a long parade of slow failures. They're released as soon as the socket closes, and a command sent
+  after that raises `Ferrum::DeadBrowserError` right away [#470]
 - A raising callback killed `Client::Subscriber`'s dispatch thread and with it every event for the rest of the
   process: pages created later raised `NoSuchTargetError`, open ones lost their execution contexts. Callbacks are
   now rescued one by one and reported to stderr [#470]

lib/ferrum/client.rb

@@ -219,6 +219,8 @@ def send_message(message, async:, timeout: nil)
         @ws.send_message(message)
         true
       else
+        raise DeadBrowserError if @ws.messages.closed?
+
         pending = Concurrent::IVar.new
         @pendings[message[:id]] = pending
         @ws.send_message(message)
@@ -340,9 +342,17 @@ def start
             @pendings[message["id"]]&.set(message)
           end
         end
+
+        release_pendings
       end
     end
 
+    # Nothing is going to answer the commands still in flight once the socket
+    # is gone, release them instead of making each wait out its timeout.
+    def release_pendings
+      @pendings.each_value { |pending| pending.try_set(nil) }
+    end
+
     # Locked so two concurrent commands never share an id and read each
     # other's responses from @pendings.
     def next_command_id

sig/ferrum/client.rbs

@@ -74,6 +74,8 @@ module Ferrum
 
     def start: () -> void
 
+    def release_pendings: () -> void
+
     def next_command_id: () -> ::Integer
 
     def raise_browser_error: (Hash[String, untyped] error) -> void

spec/client_spec.rb

@@ -1,6 +1,37 @@
 # frozen_string_literal: true
 
 describe Ferrum::Client do
+  describe "a dead connection" do
+    let(:remote) { Ferrum::Browser.new(base_url: base_url, timeout: 10, protocol_timeout: 10) }
+
+    after { remote.quit }
+
+    def messages
+      remote.client.instance_variable_get(:@ws).messages
+    end
+
+    it "releases the commands in flight" do
+      page = remote.create_page
+      Thread.new do
+        sleep(0.2)
+        messages.close
+      end
+      start = Ferrum::Utils::ElapsedTime.monotonic_time
+
+      expect { page.go_to("/really_slow") }.to raise_error(Ferrum::DeadBrowserError)
+      expect(Ferrum::Utils::ElapsedTime.elapsed_time(start)).to be < 5
+    end
+
+    it "fails the commands that follow without waiting" do
+      page = remote.create_page
+      messages.close
+      start = Ferrum::Utils::ElapsedTime.monotonic_time
+
+      expect { page.go_to("/") }.to raise_error(Ferrum::DeadBrowserError)
+      expect(Ferrum::Utils::ElapsedTime.elapsed_time(start)).to be < 1
+    end
+  end
+
   describe "event callbacks" do
     let(:remote) { Ferrum::Browser.new(base_url: base_url, timeout: 3, protocol_timeout: 3) }