From 82bc3e6a62f77f889ba0036b36efac4cb958d7c3 Mon Sep 17 00:00:00 2001
From: Ismael Celis <ismaelct@gmail.com>
Date: Thu, 24 Sep 2026 16:02:22 +0100
Subject: [PATCH] Catch exceptions that wrap known client-disconnection errors,
 trigger on_client_disconnect

Falcon server's protocol-http1 >= 0.41 now wraps Errno::ECONNRESET in its own exception class.
This change makes this library make sure to inspect an exception's cause (root exception) to check whether it's a client disconnect that should run the on_client_disconnect callbacks.
---
 lib/datastar/dispatcher.rb | 29 +++++++++++++++++-----
 spec/dispatcher_spec.rb    | 49 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 72 insertions(+), 6 deletions(-)

diff --git a/lib/datastar/dispatcher.rb b/lib/datastar/dispatcher.rb
index 56c6585..49afbd3 100644
--- a/lib/datastar/dispatcher.rb
+++ b/lib/datastar/dispatcher.rb
@@ -386,14 +386,33 @@ def wrap_socket(socket)
       @compressor.wrap_socket(socket)
     end
 
+    # Errors raised when writing to a socket the client has closed.
+    DISCONNECT_ERRORS = [IOError, Errno::EPIPE, Errno::ECONNRESET].freeze
+
+    # Whether an error means the client went away.
+    #
+    # Servers may wrap the underlying socket error in their own class
+    # (e.g. protocol-http1 >= 0.41 raises +Protocol::HTTP::RemoteError+
+    # from a +rescue Errno::EPIPE+), so the +cause+ chain is checked too.
+    #
+    # @param error [Exception]
+    # @return [Boolean]
+    def client_disconnect?(error)
+      while error
+        return true if DISCONNECT_ERRORS.any? { |klass| error.is_a?(klass) }
+
+        error = error.cause
+      end
+      false
+    end
+
     # Handle errors caught during streaming
     # @param error [Exception] the error that occurred
     # @param socket [IO] the socket to pass to error handlers
     def handle_streaming_error(error, socket)
-      case error
-      when IOError, Errno::EPIPE, Errno::ECONNRESET
+      if client_disconnect?(error)
         @on_client_disconnect.each { |callable| callable.call(socket) }
-      when Exception
+      else
         @on_error.each { |callable| callable.call(error) }
       end
     end
@@ -407,10 +426,8 @@ def handling_sync_errors(generator, socket, &)
       yield
 
       @on_server_disconnect.each { |callable| callable.call(generator) }
-    rescue IOError, Errno::EPIPE, Errno::ECONNRESET => e
-      @on_client_disconnect.each { |callable| callable.call(socket) }
     rescue Exception => e
-      @on_error.each { |callable| callable.call(e) }
+      handle_streaming_error(e, socket)
     end
 
     # Parse signals from the request
diff --git a/spec/dispatcher_spec.rb b/spec/dispatcher_spec.rb
index dd68f8c..3e8159c 100644
--- a/spec/dispatcher_spec.rb
+++ b/spec/dispatcher_spec.rb
@@ -33,6 +33,18 @@ def wait_for_close(&)
   end
 end
 
+# A server-side wrapper around the socket error, as raised by e.g.
+# protocol-http1 >= 0.41 (Protocol::HTTP::RemoteError from a rescue Errno::EPIPE).
+class WrappedDisconnectError < StandardError; end
+
+class WrappingTestSocket < TestSocket
+  def <<(line)
+    super
+  rescue Errno::EPIPE
+    raise WrappedDisconnectError, 'Remote connection closed during flush!'
+  end
+end
+
 RSpec.describe Datastar::Dispatcher do
   include DispatcherExamples
 
@@ -635,6 +647,43 @@ def self.render_in(view_context) = %(<div id="foo">\n<span>#{view_context}</span
       expect(events).to eq([true, false])
     end
 
+    specify '#on_client_disconnect when the server wraps the socket error' do
+      events = []
+      errors = []
+      dispatcher
+        .on_client_disconnect { |conn| events << :disconnect }
+        .on_error { |err| errors << err }
+
+      dispatcher.stream do |sse|
+        sse.patch_signals(foo: 'bar')
+      end
+      socket = WrappingTestSocket.new(open: false)
+
+      dispatcher.response.body.call(socket)
+      socket.wait_for_close
+      expect(events).to eq([:disconnect])
+      expect(errors).to eq([])
+    end
+
+    specify 'concurrent streams: #on_client_disconnect when the server wraps the socket error' do
+      dispatcher = Datastar.new(request:, response:, heartbeat: 0.001)
+      events = []
+      errors = []
+      dispatcher
+        .on_client_disconnect { |conn| events << :disconnect }
+        .on_error { |err| errors << err }
+
+      dispatcher.stream do |sse|
+        sleep 10
+      end
+      socket = WrappingTestSocket.new(open: false)
+
+      dispatcher.response.body.call(socket)
+      socket.wait_for_close
+      expect(events).to eq([:disconnect])
+      expect(errors).to eq([])
+    end
+
     specify '#check_connection triggers #on_client_disconnect' do
       events = []
       dispatcher