From 3e89f5ae83184ec66255d1cc96530f9d85b35539 Mon Sep 17 00:00:00 2001
From: Sebastian Sura <s.sura@hotmail.de>
Date: Tue, 3 Mar 2026 16:18:23 +0000
Subject: [PATCH] ctest: Disable pre- and post-processing during `--show-only`

Do not run the custom pre-/post- test tasks when instructed to only show
the tests that would be executed.  Otherwise it's impossible to reliably
parse the output of this as is will be contaminated by all output
produced by the pre-/post-scripts!

Fixes: #23254
---
 Source/CTest/cmCTestTestHandler.cxx              |  4 ++--
 .../CustomPrePost-show-only-stdout.txt           |  5 +++++
 .../CTestCommandLine/CustomPrePost-stdout.txt    | 10 ++++++++++
 .../RunCMake/CTestCommandLine/RunCMakeTest.cmake | 16 ++++++++++++++++
 4 files changed, 33 insertions(+), 2 deletions(-)
 create mode 100644 Tests/RunCMake/CTestCommandLine/CustomPrePost-show-only-stdout.txt
 create mode 100644 Tests/RunCMake/CTestCommandLine/CustomPrePost-stdout.txt

diff --git a/Source/CTest/cmCTestTestHandler.cxx b/Source/CTest/cmCTestTestHandler.cxx
index 806ddf5961..98094dda46 100644
--- a/Source/CTest/cmCTestTestHandler.cxx
+++ b/Source/CTest/cmCTestTestHandler.cxx
@@ -359,7 +359,7 @@ int cmCTestTestHandler::ProcessHandler()
                        << cmSystemTools::GetLogicalWorkingDirectory()
                        << std::endl,
                      this->Quiet);
-  if (!this->PreProcessHandler()) {
+  if (!this->CTest->GetShowOnly() && !this->PreProcessHandler()) {
     return -1;
   }
 
@@ -428,7 +428,7 @@ int cmCTestTestHandler::ProcessHandler()
     return 1;
   }
 
-  if (!this->PostProcessHandler()) {
+  if (!this->CTest->GetShowOnly() && !this->PostProcessHandler()) {
     this->LogFile = nullptr;
     return -1;
   }
diff --git a/Tests/RunCMake/CTestCommandLine/CustomPrePost-show-only-stdout.txt b/Tests/RunCMake/CTestCommandLine/CustomPrePost-show-only-stdout.txt
new file mode 100644
index 0000000000..971bc9a573
--- /dev/null
+++ b/Tests/RunCMake/CTestCommandLine/CustomPrePost-show-only-stdout.txt
@@ -0,0 +1,5 @@
+^Test project [^
+]+/Tests/RunCMake/CTestCommandLine/CustomPrePost
+  Test #1: Echo
+
+Total Tests: 1$
diff --git a/Tests/RunCMake/CTestCommandLine/CustomPrePost-stdout.txt b/Tests/RunCMake/CTestCommandLine/CustomPrePost-stdout.txt
new file mode 100644
index 0000000000..d06f476a78
--- /dev/null
+++ b/Tests/RunCMake/CTestCommandLine/CustomPrePost-stdout.txt
@@ -0,0 +1,10 @@
+^Test project [^
+]+/Tests/RunCMake/CTestCommandLine/CustomPrePost
+Custom Pre-Test
+    Start 1: Echo
+1/1 Test #1: Echo \.+   Passed +[0-9\.]+ sec
+
+100% tests passed, 0 tests failed out of 1
+
+Total Test time \(real\) = +[0-9\.]+ sec
+Custom Post-Test$
diff --git a/Tests/RunCMake/CTestCommandLine/RunCMakeTest.cmake b/Tests/RunCMake/CTestCommandLine/RunCMakeTest.cmake
index bb29635229..e3df1cc84b 100644
--- a/Tests/RunCMake/CTestCommandLine/RunCMakeTest.cmake
+++ b/Tests/RunCMake/CTestCommandLine/RunCMakeTest.cmake
@@ -492,6 +492,22 @@ function(show_only_json_check_python v)
   return(PROPAGATE RunCMake_TEST_FAILED)
 endfunction()
 
+block()
+  set(RunCMake_TEST_BINARY_DIR ${RunCMake_BINARY_DIR}/CustomPrePost)
+  set(RunCMake_TEST_NO_CLEAN 1)
+  file(REMOVE_RECURSE "${RunCMake_TEST_BINARY_DIR}")
+  file(MAKE_DIRECTORY "${RunCMake_TEST_BINARY_DIR}")
+  file(WRITE "${RunCMake_TEST_BINARY_DIR}/CTestCustom.cmake" "
+set(CTEST_CUSTOM_PRE_TEST \"\\\"${CMAKE_COMMAND}\\\" -E echo \\\"Custom Pre-Test\\\"\")
+set(CTEST_CUSTOM_POST_TEST \"\\\"${CMAKE_COMMAND}\\\" -E echo \\\"Custom Post-Test\\\"\")
+")
+  file(WRITE "${RunCMake_TEST_BINARY_DIR}/CTestTestfile.cmake" "
+  add_test(Echo \"${CMAKE_COMMAND}\" -E echo)
+")
+  run_cmake_command(CustomPrePost ${CMAKE_CTEST_COMMAND})
+  run_cmake_command(CustomPrePost-show-only ${CMAKE_CTEST_COMMAND} --show-only=human)
+endblock()
+
 function(run_ShowOnly)
   set(RunCMake_TEST_BINARY_DIR ${RunCMake_BINARY_DIR}/ShowOnly)
   set(RunCMake_TEST_NO_CLEAN 1)