Merge pull request #18993 from alalek:issue_18984

cmake/OpenCVFindLibsGrfmt.cmake

@@ -6,6 +6,7 @@
 if(BUILD_ZLIB)
   ocv_clear_vars(ZLIB_FOUND)
 else()
+  ocv_clear_internal_cache_vars(ZLIB_LIBRARY ZLIB_INCLUDE_DIR)
   find_package(ZLIB "${MIN_VER_ZLIB}")
   if(ZLIB_FOUND AND ANDROID)
     if(ZLIB_LIBRARIES MATCHES "/usr/(lib|lib32|lib64)/libz.so$")
@@ -31,11 +32,12 @@ if(WITH_JPEG)
   if(BUILD_JPEG)
     ocv_clear_vars(JPEG_FOUND)
   else()
+    ocv_clear_internal_cache_vars(JPEG_LIBRARY JPEG_INCLUDE_DIR)
     include(FindJPEG)
   endif()
 
   if(NOT JPEG_FOUND)
-    ocv_clear_vars(JPEG_LIBRARY JPEG_LIBRARIES JPEG_INCLUDE_DIR)
+    ocv_clear_vars(JPEG_LIBRARY JPEG_INCLUDE_DIR)
 
     if(NOT BUILD_JPEG_TURBO_DISABLE)
       set(JPEG_LIBRARY libjpeg-turbo CACHE INTERNAL "")
@@ -76,6 +78,7 @@ if(WITH_TIFF)
   if(BUILD_TIFF)
     ocv_clear_vars(TIFF_FOUND)
   else()
+    ocv_clear_internal_cache_vars(TIFF_LIBRARY TIFF_INCLUDE_DIR)
     include(FindTIFF)
     if(TIFF_FOUND)
       ocv_parse_header("${TIFF_INCLUDE_DIR}/tiff.h" TIFF_VERSION_LINES TIFF_VERSION_CLASSIC TIFF_VERSION_BIG TIFF_VERSION TIFF_BIGTIFF_VERSION)
@@ -119,6 +122,7 @@ if(WITH_WEBP)
   if(BUILD_WEBP)
     ocv_clear_vars(WEBP_FOUND WEBP_LIBRARY WEBP_LIBRARIES WEBP_INCLUDE_DIR)
   else()
+    ocv_clear_internal_cache_vars(WEBP_LIBRARY WEBP_INCLUDE_DIR)
     include(cmake/OpenCVFindWebP.cmake)
     if(WEBP_FOUND)
       set(HAVE_WEBP 1)
@@ -184,6 +188,7 @@ if(WITH_PNG)
   if(BUILD_PNG)
     ocv_clear_vars(PNG_FOUND)
   else()
+    ocv_clear_internal_cache_vars(PNG_LIBRARY PNG_INCLUDE_DIR)
     include(FindPNG)
     if(PNG_FOUND)
       include(CheckIncludeFile)
@@ -215,6 +220,7 @@ endif()
 if(WITH_OPENEXR)
   ocv_clear_vars(HAVE_OPENEXR)
   if(NOT BUILD_OPENEXR)
+    ocv_clear_internal_cache_vars(OPENEXR_INCLUDE_PATHS OPENEXR_LIBRARIES OPENEXR_ILMIMF_LIBRARY OPENEXR_VERSION)
     include("${OpenCV_SOURCE_DIR}/cmake/OpenCVFindOpenEXR.cmake")
   endif()
 

cmake/OpenCVUtils.cmake

@@ -400,6 +400,24 @@ macro(ocv_clear_vars)
   endforeach()
 endmacro()
 
+
+# Clears passed variables with INTERNAL type from CMake cache
+macro(ocv_clear_internal_cache_vars)
+  foreach(_var ${ARGN})
+    get_property(_propertySet CACHE ${_var} PROPERTY TYPE SET)
+    if(_propertySet)
+      get_property(_type CACHE ${_var} PROPERTY TYPE)
+      if(_type STREQUAL "INTERNAL")
+        message("Cleaning INTERNAL cached variable: ${_var}")
+        unset(${_var} CACHE)
+      endif()
+    endif()
+  endforeach()
+  unset(_propertySet)
+  unset(_type)
+endmacro()
+
+
 set(OCV_COMPILER_FAIL_REGEX
     "argument .* is not valid"                  # GCC 9+ (including support of unicode quotes)
     "command[- ]line option .* is valid for .* but not for C\\+\\+" # GNU