From 11faf28fed65e0714adb1331d15e38cbb8e27b21 Mon Sep 17 00:00:00 2001
From: Klemens Morgenstern <klemens.morgenstern@gmx.net>
Date: Sun, 11 Jan 2026 07:08:46 +0800
Subject: [PATCH] Added test for #491

---
 .../process/v2/windows/default_launcher.hpp   |  4 +-
 test/v2/process.cpp                           | 51 +++++++++++++++++++
 2 files changed, 53 insertions(+), 2 deletions(-)

diff --git a/include/boost/process/v2/windows/default_launcher.hpp b/include/boost/process/v2/windows/default_launcher.hpp
index 16ff12d46..763681250 100644
--- a/include/boost/process/v2/windows/default_launcher.hpp
+++ b/include/boost/process/v2/windows/default_launcher.hpp
@@ -97,7 +97,7 @@ inline void invoke_on_error(Launcher & /*launcher*/, const filesystem::path &/*e
 template<typename Launcher, typename Init>
 inline auto invoke_on_error(Launcher & launcher, const filesystem::path &executable, std::wstring &cmd_line,
                             const error_code & ec, Init && init, derived && )
--> decltype(init.on_error(launcher, executable, cmd_line, ec))
+    -> decltype(init.on_error(launcher, executable, cmd_line, ec))
 {
   init.on_error(launcher, executable, cmd_line, ec);
 }
@@ -109,7 +109,7 @@ inline std::false_type probe_on_error(
 
 template<typename Launcher, typename Init>
 inline auto probe_on_error(Launcher & launcher, Init && init, derived && )
-        -> std::is_same<error_code, decltype(init.on_error(launcher, std::declval<const filesystem::path &>(), std::declval<std::wstring &>(), std::declval<error_code&>()))>;
+        -> std::is_same<void, decltype(init.on_error(launcher, std::declval<const filesystem::path &>(), std::declval<std::wstring &>(), std::declval<error_code&>()))>;
 
 template<typename Launcher, typename Init>
 using has_on_error = decltype(probe_on_error(std::declval<Launcher&>(), std::declval<Init>(), derived{}));
diff --git a/test/v2/process.cpp b/test/v2/process.cpp
index 14d3ec801..161981ae6 100644
--- a/test/v2/process.cpp
+++ b/test/v2/process.cpp
@@ -933,5 +933,56 @@ BOOST_AUTO_TEST_CASE(print_args_combined)
   BOOST_CHECK_EQUAL(proc.exit_code(), 0);
 }
 
+
+struct my_handler
+{
+    boost::process::filesystem::path pt;
+    bpv::error_code ec;
+
+    template<typename Launcher, typename CmdLine>
+    bpv::error_code on_setup(Launcher &launcher, const bpv::filesystem::path& executable,
+                  CmdLine (&/*cmd_line*/))
+    {
+      pt = executable;
+      if (executable == "/send/more/cops")
+        return asio::error::no_recovery;
+      else
+        return {};
+    }
+
+    template<typename Launcher, typename CmdLine>
+    void on_error(Launcher &launcher, const bpv::filesystem::path& executable,
+                  CmdLine (&/*cmd_line*/), const bpv::error_code & ec)
+    {
+      this->ec = ec;
+    }
+
+    template<typename Launcher, typename CmdLine>
+    void on_success(Launcher &launcher, const bpv::filesystem::path& executable,
+                  CmdLine (&/*cmd_line*/))
+    {
+      ec.clear();
+    }
+  };
+
+BOOST_AUTO_TEST_CASE(custom_handlers)
+{
+  my_handler mh;
+
+  asio::io_context ctx;
+  
+  BOOST_CHECK_THROW(bpv::process(ctx, "/send/more/cops", {}, mh), bpv::system_error);
+  BOOST_CHECK_EQUAL(mh.ec, asio::error::no_recovery);
+  
+  BOOST_CHECK_EQUAL(mh.pt, "/send/more/cops");
+
+  using boost::unit_test::framework::master_test_suite;
+  const auto pth = bpv::filesystem::absolute(master_test_suite().argv[1]);
+
+  bpv::process proc(ctx, pth, {}, mh);
+
+  BOOST_CHECK_EQUAL(mh.pt, pth);
+}
+
 BOOST_AUTO_TEST_SUITE_END();