Add a CMAKE option to completely disable Python (#60463)

CMakeLists.txt

@@ -17,7 +17,9 @@ endif()
 # don't relink it only the shared object changes
 set(CMAKE_LINK_DEPENDS_NO_SHARED ON)
 
-set (WITH_BINDINGS TRUE CACHE BOOL "Determines whether Python bindings should be built")
+option (WITH_PYTHON "Determines whether Python support should be built (disabling it will in particular disable processing)" ON)
+set(WITH_BINDINGS ${WITH_PYTHON} CACHE BOOL "Determines whether Python bindings should be built")
+
 set (WITH_3D TRUE CACHE BOOL "Determines whether QGIS 3D library should be built")
 set (WITH_QGIS_PROCESS TRUE CACHE BOOL "Determines whether the standalone \"qgis_process\" tool should be built")
 set (WITH_DESKTOP TRUE CACHE BOOL "Determines whether QGIS desktop should be built")
@@ -317,8 +319,11 @@ if(WITH_CORE)
     # The qgis_desktop target is meant to build a minimal but complete running QGIS during development
     # This should help to reduce compile time while still having a "complete enough" QGIS for most of the development
     add_custom_target(qgis_desktop
-      DEPENDS qgis qgispython pycore pygui pyanalysis provider_postgres staged-plugins pyplugin-installer resources svg doc icons
+      DEPENDS qgis provider_postgres staged-plugins resources svg doc icons
     )
+    if ( WITH_PYTHON )
+      add_dependencies(qgis_desktop qgispython pycore pygui pyanalysis staged-plugins pyplugin-installer )
+    endif()
   endif()
 
   # try to configure and build MDAL support
@@ -1181,7 +1186,6 @@ if (WITH_CORE AND WITH_BINDINGS)
   endif()
 endif()
 
-
 #############################################################
 # create qgsconfig.h
 # installed with app target

INSTALL.md

@@ -361,6 +361,7 @@ QGIS build is tunable according to your needs. Many flags are available to activ
 * `WITH_ORACLE`: Determines whether Oracle support should be built
 * `WITH_PDAL`: Determines whether PDAL support should be built
 * `WITH_POSTGRESQL`: Determines whether POSTGRESQL support should be built
+* `WITH_PYTHON`: Determines whether Python support should be built (disabling it will in particular disable processing)
 * `WITH_QGIS_PROCESS`: Determines whether the standalone \"qgis_process\" tool should be built
 * `WITH_QSPATIALITE`: Determines whether QSPATIALITE sql driver should be built
 * `WITH_SERVER`: Determines whether QGIS server should be built

src/app/CMakeLists.txt

@@ -567,12 +567,17 @@ target_include_directories(qgis_app PUBLIC
   ${CMAKE_SOURCE_DIR}/src/app/tiledscene
   ${CMAKE_SOURCE_DIR}/src/app/vectortile
   ${CMAKE_SOURCE_DIR}/src/plugins
-  ${CMAKE_SOURCE_DIR}/src/python
   ${CMAKE_SOURCE_DIR}/src/native
 
   ${CMAKE_BINARY_DIR}/src/app
 )
 
+if (WITH_PYTHON)
+  target_include_directories(qgis_app PUBLIC
+    ${CMAKE_SOURCE_DIR}/src/python
+  )
+endif()
+
 if (WITH_3D)
   target_include_directories(qgis_app PUBLIC
     ${CMAKE_SOURCE_DIR}/src/app/3d