FindBISON: Fix CMP0088 NEW behavior for non-absolute input paths

Now that the working directory is in the build tree, relative input
paths must be converted to an absolute path to remain relative to the
source directory.

Fixes: #19472

2 files changed, 17 insertions, 3 deletions

diff --git a/Help/release/3.14.rst b/Help/release/3.14.rst
index e3a7a62..229d8dc 100644
--- a/Help/release/3.14.rst
+++ b/Help/release/3.14.rst
@@ -420,3 +420,11 @@ Changes made since CMake 3.14.0 include the following.
   from explicit use via :command:`include_directories` and
   :command:`target_include_directories` as they were in CMake 3.14.0
   through 3.14.4.
+
+3.14.6
+------
+
+* In CMake 3.14.0 through 3.14.5, the :module:`FindBISON` module
+  policy :policy:`CMP0088` ``NEW`` behavior accidentally interpreted
+  a relative path to the ``.y`` input as relative to the build tree
+  directory instead of the source tree directory.  This has been fixed.
diff --git a/Modules/FindBISON.cmake b/Modules/FindBISON.cmake
index 06ac2d9..c6c8de0 100644
--- a/Modules/FindBISON.cmake
+++ b/Modules/FindBISON.cmake
@@ -257,15 +257,19 @@ if(BISON_EXECUTABLE)
         PARENT_SCOPE # undocumented, do not use outside of CMake
         )
       set(_BISON_WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR})
+      set(_BisonInput "${BisonInput}")
       if("x${_BISON_CMP0088}x" STREQUAL "xNEWx")
         set(_BISON_WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})
+        if(NOT IS_ABSOLUTE "${_BisonInput}")
+          set(_BisonInput "${CMAKE_CURRENT_SOURCE_DIR}/${_BisonInput}")
+        endif()
       endif()
       unset(_BISON_CMP0088)
 
       add_custom_command(OUTPUT ${BISON_TARGET_outputs}
-        COMMAND ${BISON_EXECUTABLE} ${BISON_TARGET_cmdopt} -o ${BisonOutput} ${BisonInput}
+        COMMAND ${BISON_EXECUTABLE} ${BISON_TARGET_cmdopt} -o ${BisonOutput} ${_BisonInput}
         VERBATIM
-        DEPENDS ${BisonInput}
+        DEPENDS ${_BisonInput}
         COMMENT "[BISON][${Name}] Building parser with bison ${BISON_VERSION}"
         WORKING_DIRECTORY ${_BISON_WORKING_DIRECTORY})
 
@@ -273,12 +277,14 @@ if(BISON_EXECUTABLE)
 
       # define target variables
       set(BISON_${Name}_DEFINED TRUE)
-      set(BISON_${Name}_INPUT ${BisonInput})
+      set(BISON_${Name}_INPUT ${_BisonInput})
       set(BISON_${Name}_OUTPUTS ${BISON_TARGET_outputs} ${BISON_TARGET_extraoutputs})
       set(BISON_${Name}_COMPILE_FLAGS ${BISON_TARGET_cmdopt})
       set(BISON_${Name}_OUTPUT_SOURCE "${BisonOutput}")
       set(BISON_${Name}_OUTPUT_HEADER "${BISON_TARGET_output_header}")
 
+      unset(_BisonInput)
+
     endif()
   endmacro()
   #