CMake: rename GDAL_FIND_PACKAGE_PROJ_METHOD to GDAL_FIND_PACKAGE_PROJ…

…_MODE, and only add find_dependency() in static builds

cmake/helpers/CheckDependentLibraries.cmake

@@ -378,23 +378,36 @@ if (GDAL_USE_CRYPTOPP)
   option(CRYPTOPP_USE_ONLY_CRYPTODLL_ALG "Use Only cryptoDLL alg. only work on dynamic DLL" OFF)
 endif ()
 
-set(GDAL_FIND_PACKAGE_PROJ_METHOD "CONFIG" CACHE STRING "Method to use for find_package(PROJ): CONFIG or MODULE")
-set_property(CACHE GDAL_FIND_PACKAGE_PROJ_METHOD PROPERTY STRINGS "CONFIG" "MODULE")
-mark_as_advanced(GDAL_FIND_PACKAGE_PROJ_METHOD)
-if(GDAL_FIND_PACKAGE_PROJ_METHOD STREQUAL "MODULE")
-    find_package(PROJ MODULE REQUIRED)
-    string(APPEND GDAL_IMPORT_DEPENDENCIES "find_dependency(PROJ MODULE REQUIRED)\n")
+set(GDAL_FIND_PACKAGE_PROJ_MODE "CUSTOM" CACHE STRING "Mode to use for find_package(PROJ): CUSTOM, CONFIG, MODULE or empty string")
+set_property(CACHE GDAL_FIND_PACKAGE_PROJ_MODE PROPERTY STRINGS "CUSTOM" "CONFIG" "MODULE" "")
+if(NOT GDAL_FIND_PACKAGE_PROJ_MODE STREQUAL "CUSTOM")
+    find_package(PROJ ${GDAL_FIND_PACKAGE_PROJ_MODE} REQUIRED)
+    if (NOT BUILD_SHARED_LIBS)
+        string(APPEND GDAL_IMPORT_DEPENDENCIES "find_dependency(PROJ ${GDAL_FIND_PACKAGE_PROJ_MODE})\n")
+    endif()
 else()
     # First check with CMake config files, and then fallback to the FindPROJ module.
     find_package(PROJ CONFIG)
+    if (PROJ_FOUND AND PROJ_VERSION VERSION_LESS "8")
+        message(WARNING "PROJ ${PROJ_VERSION} < 8 found with Config file. As it is not trusted, retrying with module mode")
+    endif()
     if (PROJ_FOUND)
-      string(APPEND GDAL_IMPORT_DEPENDENCIES "find_dependency(PROJ ${PROJ_VERSION_MAJOR} CONFIG)\n")
+      if (NOT BUILD_SHARED_LIBS)
+        string(APPEND GDAL_IMPORT_DEPENDENCIES "find_dependency(PROJ CONFIG)\n")
+      endif()
     else()
-      find_package(PROJ 6.3 REQUIRED)
-      string(APPEND GDAL_IMPORT_DEPENDENCIES "find_dependency(PROJ 6.3)\n")
+      find_package(PROJ REQUIRED)
+      if (NOT BUILD_SHARED_LIBS)
+        string(APPEND GDAL_IMPORT_DEPENDENCIES "find_dependency(PROJ)\n")
+      endif()
     endif ()
 endif()
-
+if (DEFINED PROJ_VERSION_STRING AND NOT DEFINED PROJ_VERSION)
+    set(PROJ_VERSION ${PROJ_VERSION_STRING})
+endif()
+if ("${PROJ_VERSION}" VERSION_LESS "6.3")
+    message(FATAL_ERROR "PROJ >= 6.3 required. Version ${PROJ_VERSION} found")
+endif()
 
 gdal_check_package(TIFF "Support for the Tag Image File Format (TIFF)." VERSION 4.1 CAN_DISABLE)
 set_package_properties(

doc/source/development/building_from_source.rst

@@ -1681,7 +1681,7 @@ the :ref:`vector.pg` and :ref:`raster.postgisraster` drivers.
 PROJ
 ****
 
-`PROJ <https://github.com/OSGeo/PROJ/>`_ >= 6 is a *required* dependency for GDAL.
+`PROJ <https://github.com/OSGeo/PROJ/>`_ >= 6.3 is a *required* dependency for GDAL.
 
 .. option:: PROJ_INCLUDE_DIR
 
@@ -1694,6 +1694,17 @@ PROJ
     ``PROJ_LIBRARY_DEBUG`` can also be specified to a similar library for
     building Debug releases.
 
+.. option:: GDAL_FIND_PACKAGE_PROJ_MODE=CUSTOM/MODULE/CONFIG/empty string
+
+    .. versionadded:: 3.9
+
+    Control the mode used for find_package(PROJ).
+    Alters how the default CMake seach logic
+    (https://cmake.org/cmake/help/latest/command/find_package.html) applies.
+    Defaults to CUSTOM, where the CONFIG mode is applied for PROJ >= 8, and
+    fallbacks to default MODULE mode otherwise.
+    Other values are passed directly to find_package()
+
 QHULL
 *****