From c01d4e76985a01e6443eb26ae4ee6288b891c6f6 Mon Sep 17 00:00:00 2001
From: Peter Kokot <peterkokot@gmail.com>
Date: Mon, 23 Dec 2024 17:47:30 +0100
Subject: [PATCH] FindBISON, FindFLEX: Create output directories

Bison and Flex executables at the time of writing don't create
output directories when generating files. In most cases this isn't issue
if the build directory is created before running bison or flex. If any
of the output directories that can be determined isn't available, these
modules now create them before running the bison or flex command.

Issue: #19529
---
 Modules/FindBISON.cmake | 22 +++++++++++++++++++++-
 Modules/FindFLEX.cmake  | 22 +++++++++++++++++++++-
 2 files changed, 42 insertions(+), 2 deletions(-)

diff --git a/Modules/FindBISON.cmake b/Modules/FindBISON.cmake
index 6d0ace7aad..50205e662b 100644
--- a/Modules/FindBISON.cmake
+++ b/Modules/FindBISON.cmake
@@ -276,7 +276,27 @@ if(BISON_EXECUTABLE)
       endif()
       unset(_BISON_CMP0088)
 
+      # Bison cannot create output directories. Create any missing determined
+      # directories where the files will be generated if they don't exist yet.
+      set(_BisonMakeDirectoryCommand "")
+      foreach(output IN LISTS BISON_TARGET_outputs)
+        cmake_path(GET output PARENT_PATH dir)
+        if(dir)
+          list(APPEND _BisonMakeDirectoryCommand ${dir})
+        endif()
+        unset(dir)
+      endforeach()
+      if(_BisonMakeDirectoryCommand)
+        list(REMOVE_DUPLICATES _BisonMakeDirectoryCommand)
+        list(
+          PREPEND
+          _BisonMakeDirectoryCommand
+          COMMAND ${CMAKE_COMMAND} -E make_directory
+        )
+      endif()
+
       add_custom_command(OUTPUT ${BISON_TARGET_outputs}
+        ${_BisonMakeDirectoryCommand}
         COMMAND ${BISON_EXECUTABLE} ${BISON_TARGET_cmdopt} -o ${BisonOutput} ${_BisonInput}
         VERBATIM
         DEPENDS ${_BisonInput}
@@ -295,7 +315,7 @@ if(BISON_EXECUTABLE)
       set(BISON_${Name}_OUTPUT_HEADER "${BISON_TARGET_output_header}")
 
       unset(_BisonInput)
-
+      unset(_BisonMakeDirectoryCommand)
     endif()
   endmacro()
   #
diff --git a/Modules/FindFLEX.cmake b/Modules/FindFLEX.cmake
index e67e931125..a7f127b370 100644
--- a/Modules/FindFLEX.cmake
+++ b/Modules/FindFLEX.cmake
@@ -211,8 +211,28 @@ if(FLEX_EXECUTABLE)
         list(APPEND _flex_EXE_OPTS --header-file=${_flex_OUTPUT_HEADER_ABS})
       endif()
 
+      # Flex cannot create output directories. Create any missing determined
+      # directories where the files will be generated if they don't exist yet.
+      set(_flex_MAKE_DIRECTORY_COMMAND "")
+      foreach(output IN LISTS _flex_TARGET_OUTPUTS)
+        cmake_path(GET output PARENT_PATH dir)
+        if(dir)
+          list(APPEND _flex_MAKE_DIRECTORY_COMMAND ${dir})
+        endif()
+        unset(dir)
+      endforeach()
+      if(_flex_MAKE_DIRECTORY_COMMAND)
+        list(REMOVE_DUPLICATES _flex_MAKE_DIRECTORY_COMMAND)
+        list(
+          PREPEND
+          _flex_MAKE_DIRECTORY_COMMAND
+          COMMAND ${CMAKE_COMMAND} -E make_directory
+        )
+      endif()
+
       get_filename_component(_flex_EXE_NAME_WE "${FLEX_EXECUTABLE}" NAME_WE)
       add_custom_command(OUTPUT ${_flex_TARGET_OUTPUTS}
+        ${_flex_MAKE_DIRECTORY_COMMAND}
         COMMAND ${FLEX_EXECUTABLE} ${_flex_EXE_OPTS} -o${_flex_OUTPUT} ${_flex_INPUT}
         VERBATIM
         DEPENDS ${_flex_INPUT}
@@ -228,12 +248,12 @@ if(FLEX_EXECUTABLE)
       unset(_flex_EXE_NAME_WE)
       unset(_flex_EXE_OPTS)
       unset(_flex_INPUT)
+      unset(_flex_MAKE_DIRECTORY_COMMAND)
       unset(_flex_OUTPUT)
       unset(_flex_OUTPUT_HEADER)
       unset(_flex_OUTPUT_HEADER_ABS)
       unset(_flex_TARGET_OUTPUTS)
       unset(_flex_WORKING_DIR)
-
     endif()
   endmacro()
   #============================================================