FindMatlab: Prefer to use VersionInfo.xml to get version, fallback to run

Parsing the version file is much faster than running Matlab.
It also improves reliability as Matlab silently quits or hangs
in some misconfigured environments.

For old Matlab, falls back to running Matlab.

also refactor file(STRINGS => file(READ as whole file was read anyway

Fixes: #25209

Modules/FindMatlab.cmake

@@ -1290,7 +1290,7 @@ function(_Matlab_get_version_from_root matlab_root matlab_or_mcr matlab_known_ve
 
     if(EXISTS "${matlab_root}/appdata/version.xml")
       # we inspect the application version.xml file that contains the product information
-      file(STRINGS "${matlab_root}/appdata/version.xml" productinfo_string NEWLINE_CONSUME)
+      file(READ "${matlab_root}/appdata/version.xml" productinfo_string)
       string(REGEX MATCH "<installedProductData.*displayedString=\"([a-zA-Z ]+)\".*/>"
              product_reg_match
              ${productinfo_string}
@@ -1363,8 +1363,14 @@ function(_Matlab_get_version_from_root matlab_root matlab_or_mcr matlab_known_ve
         ${_matlab_main_real_path_tmp}
         CACHE INTERNAL "internal matlab location for the discovered version" FORCE)
 
-    set(matlab_list_of_all_versions)
-    matlab_get_version_from_matlab_run("${Matlab_PROG_VERSION_STRING_AUTO_DETECT}" matlab_list_of_all_versions)
+    _Matlab_VersionInfoXML()
+    if(Matlab_VERSION_STRING_INTERNAL AND NOT Matlab_VERSION_STRING_INTERNAL STREQUAL "unknown")
+      # at least back to R2016 VersionInfo.xml exists
+      set(matlab_list_of_all_versions ${Matlab_VERSION_STRING_INTERNAL})
+    else()
+      # time consuming, less stable way to find Matlab version by running Matlab
+      matlab_get_version_from_matlab_run("${Matlab_PROG_VERSION_STRING_AUTO_DETECT}" matlab_list_of_all_versions)
+    endif()
 
     list(LENGTH matlab_list_of_all_versions list_of_all_versions_length)
     if(list_of_all_versions_length GREATER 0)
@@ -1381,32 +1387,45 @@ function(_Matlab_get_version_from_root matlab_root matlab_or_mcr matlab_known_ve
       message(WARNING "[MATLAB] Found several versions, taking the first one (versions found ${matlab_list_of_all_versions})")
     endif()
 
-    # return the updated value
-    set(${matlab_final_version} ${Matlab_VERSION_STRING_INTERNAL} PARENT_SCOPE)
-  elseif(EXISTS "${matlab_root}/VersionInfo.xml")
+  else()
     # MCR
     # we cannot run anything in order to extract the version. We assume that the file
     # VersionInfo.xml exists under the MatlabRoot, we look for it and extract the version from there
-    set(_matlab_version_tmp "unknown")
-    file(STRINGS "${matlab_root}/VersionInfo.xml" versioninfo_string NEWLINE_CONSUME)
-
-    if(versioninfo_string)
-      # parses "<version>9.2.0.538062</version>"
-      string(REGEX MATCH "<version>(.*)</version>"
-             version_reg_match
-             ${versioninfo_string}
-            )
+    _Matlab_VersionInfoXML()
+  endif() # Matlab or MCR
 
-      if(CMAKE_MATCH_1 MATCHES "(([0-9]+)\\.([0-9]+))[\\.0-9]*")
-        set(_matlab_version_tmp "${CMAKE_MATCH_1}")
-      endif()
+  # return the updated value
+  set(${matlab_final_version} ${Matlab_VERSION_STRING_INTERNAL} PARENT_SCOPE)
+
+endfunction()
+
+
+function(_Matlab_VersionInfoXML)
+
+  set(_matlab_version_tmp "unknown")
+
+  set(_XMLfile ${matlab_root}/VersionInfo.xml)
+  if(NOT EXISTS ${_XMLfile})
+    return()
+  endif()
+
+  file(READ ${_XMLfile} versioninfo_string)
+
+  if(versioninfo_string)
+    # parses "<version>9.2.0.538062</version>"
+    string(REGEX MATCH "<version>(.*)</version>"
+      version_reg_match
+      ${versioninfo_string}
+      )
+
+    if(CMAKE_MATCH_1 MATCHES "(([0-9]+)\\.([0-9]+))[\\.0-9]*")
+      set(_matlab_version_tmp "${CMAKE_MATCH_1}")
     endif()
-    set(${matlab_final_version} "${_matlab_version_tmp}" PARENT_SCOPE)
-    set(Matlab_VERSION_STRING_INTERNAL
-        "${_matlab_version_tmp}"
-        CACHE INTERNAL "Matlab (MCR) version (automatically determined)"
-        FORCE)
-  endif() # Matlab or MCR
+  endif()
+
+  if(_matlab_version_tmp)
+    set(Matlab_VERSION_STRING_INTERNAL "${_matlab_version_tmp}" CACHE INTERNAL "Matlab version" FORCE)
+  endif()
 
 endfunction()