Find: find_package prefers variable CMAKE_FIND_USE_REGISTRY

CMake's find control flags should all have a consistent name.
To make this happen we are introducing `CMAKE_FIND_USE_REGISTRY`
and deprecating `CMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY`.

Help/command/find_package.rst

@@ -330,8 +330,10 @@ enabled.
 
 6. Search paths stored in the CMake :ref:`User Package Registry`.
    This can be skipped if ``NO_CMAKE_PACKAGE_REGISTRY`` is passed or by
-   setting the :variable:`CMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY`
-   to ``TRUE``.
+   setting the variable :variable:`CMAKE_FIND_USE_PACKAGE_REGISTRY`
+   to ``FALSE`` or the deprecated variable
+   :variable:`CMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY` to ``TRUE``.
+
    See the :manual:`cmake-packages(7)` manual for details on the user
    package registry.
 

Help/manual/cmake-packages.7.rst

@@ -654,8 +654,13 @@ allows one to disable them using the following variables:
   :command:`export(PACKAGE)` populates the user package registry unless
   the :variable:`CMAKE_EXPORT_NO_PACKAGE_REGISTRY` variable explicitly
   disables it.
-* :variable:`CMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY` disables the
-  User Package Registry in all the :command:`find_package` calls.
+* :variable:`CMAKE_FIND_USE_PACKAGE_REGISTRY` disables the
+  User Package Registry in all the :command:`find_package` calls when
+  set to ``FALSE``.
+* Deprecated :variable:`CMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY` disables the
+  User Package Registry in all the :command:`find_package` calls when set
+  to ``TRUE``. This variable is ignored when
+  :variable:`CMAKE_FIND_USE_PACKAGE_REGISTRY` has been set.
 * :variable:`CMAKE_FIND_PACKAGE_NO_SYSTEM_PACKAGE_REGISTRY` disables
   the System Package Registry in all the :command:`find_package` calls.
 

Help/manual/cmake-variables.7.rst

@@ -183,6 +183,7 @@ Variables that Change Behavior
    /variable/CMAKE_FIND_USE_CMAKE_ENVIRONMENT_PATH
    /variable/CMAKE_FIND_USE_CMAKE_PATH
    /variable/CMAKE_FIND_USE_CMAKE_SYSTEM_PATH
+   /variable/CMAKE_FIND_USE_PACKAGE_REGISTRY
    /variable/CMAKE_FIND_USE_PACKAGE_ROOT_PATH
    /variable/CMAKE_FIND_USE_SYSTEM_ENVIRONMENT_PATH
    /variable/CMAKE_FRAMEWORK_PATH

Help/release/dev/add_cmake_find_use_package_registry.rst

@@ -0,0 +1,11 @@
+add_cmake_find_use_package_registry
+-----------------------------------
+
+* The :command:`find_package` command has learned to check the following
+  variables to control searching
+
+  * :variable:`CMAKE_FIND_USE_PACKAGE_REGISTRY` - Controls the searching the
+    cmake user registry.
+
+* The :variable:`CMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY` has been deprecated.
+  Instead use :variable:`CMAKE_FIND_USE_PACKAGE_REGISTRY`

Help/variable/CMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY.rst

@@ -1,12 +1,23 @@
 CMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY
 --------------------------------------
 
-Skip :ref:`User Package Registry` in :command:`find_package` calls.
+.. deprecated:: 3.16
+
+  Use the :variable:`CMAKE_FIND_USE_PACKAGE_REGISTRY` variable instead.
+
+By default this variable is not set. If neither
+:variable:`CMAKE_FIND_USE_PACKAGE_REGISTRY` nor
+``CMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY`` is set, then
+:command:`find_package()` will use the `User Package Registry` unless the
+`NO_CMAKE_PACKAGE_REGISTRY` option is provided.
+
+``CMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY`` is ignored if
+:variable:`CMAKE_FIND_USE_PACKAGE_REGISTRY` is set.
 
 In some cases, for example to locate only system wide installations, it
 is not desirable to use the :ref:`User Package Registry` when searching
 for packages. If the :variable:`CMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY`
-variable is enabled, all the :command:`find_package` commands will skip
+variable is ``TRUE``, all the :command:`find_package` commands will skip
 the :ref:`User Package Registry` as if they were called with the
 ``NO_CMAKE_PACKAGE_REGISTRY`` argument.
 

Help/variable/CMAKE_FIND_USE_CMAKE_ENVIRONMENT_PATH.rst

@@ -14,4 +14,5 @@ commands take precedence over this variable.
 See also the :variable:`CMAKE_FIND_USE_CMAKE_PATH`,
 :variable:`CMAKE_FIND_USE_CMAKE_SYSTEM_PATH`,
 :variable:`CMAKE_FIND_USE_SYSTEM_ENVIRONMENT_PATH`,
+:variable:`CMAKE_FIND_USE_PACKAGE_REGISTRY`,
 and :variable:`CMAKE_FIND_USE_PACKAGE_ROOT_PATH` variables.

Help/variable/CMAKE_FIND_USE_CMAKE_PATH.rst

@@ -14,4 +14,5 @@ commands take precedence over this variable.
 See also the :variable:`CMAKE_FIND_USE_CMAKE_ENVIRONMENT_PATH`,
 :variable:`CMAKE_FIND_USE_CMAKE_SYSTEM_PATH`,
 :variable:`CMAKE_FIND_USE_SYSTEM_ENVIRONMENT_PATH`,
+:variable:`CMAKE_FIND_USE_PACKAGE_REGISTRY`,
 and :variable:`CMAKE_FIND_USE_PACKAGE_ROOT_PATH` variables.

Help/variable/CMAKE_FIND_USE_CMAKE_SYSTEM_PATH.rst

@@ -14,4 +14,5 @@ commands take precedence over this variable.
 See also the :variable:`CMAKE_FIND_USE_CMAKE_PATH`,
 :variable:`CMAKE_FIND_USE_CMAKE_ENVIRONMENT_PATH`,
 :variable:`CMAKE_FIND_USE_SYSTEM_ENVIRONMENT_PATH`,
+:variable:`CMAKE_FIND_USE_PACKAGE_REGISTRY`,
 and :variable:`CMAKE_FIND_USE_PACKAGE_ROOT_PATH` variables.

Help/variable/CMAKE_FIND_USE_PACKAGE_REGISTRY.rst

@@ -0,0 +1,29 @@
+CMAKE_FIND_USE_PACKAGE_REGISTRY
+-------------------------------
+
+Controls the searching the :ref:`User Package Registry` by the :command:`find_package`
+command.
+
+By default this variable is not set and the behavior will fall back
+to that determined by the deprecated :variable:`CMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY`
+variable.  If that is also not set, then `find_package()` will use the
+`User Package Registry` unless the `NO_CMAKE_PACKAGE_REGISTRY` option
+is provided.
+
+This variable takes precedence over :variable:`CMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY`
+when both are set.
+
+In some cases, for example to locate only system wide installations, it
+is not desirable to use the :ref:`User Package Registry` when searching
+for packages. If the :variable:`CMAKE_FIND_USE_PACKAGE_REGISTRY`
+variable is ``FALSE``, all the :command:`find_package` commands will skip
+the :ref:`User Package Registry` as if they were called with the
+``NO_CMAKE_PACKAGE_REGISTRY`` argument.
+
+See also :ref:`Disabling the Package Registry`.
+
+See also the :variable:`CMAKE_FIND_USE_CMAKE_PATH`,
+:variable:`CMAKE_FIND_USE_CMAKE_ENVIRONMENT_PATH`,
+:variable:`CMAKE_FIND_USE_CMAKE_SYSTEM_PATH`,
+:variable:`CMAKE_FIND_USE_SYSTEM_ENVIRONMENT_PATH`,
+and :variable:`CMAKE_FIND_USE_PACKAGE_ROOT_PATH` variables.

Help/variable/CMAKE_FIND_USE_PACKAGE_ROOT_PATH.rst

@@ -14,4 +14,5 @@ commands take precedence over this variable.
 See also the :variable:`CMAKE_FIND_USE_CMAKE_PATH`,
 :variable:`CMAKE_FIND_USE_CMAKE_ENVIRONMENT_PATH`,
 :variable:`CMAKE_FIND_USE_CMAKE_SYSTEM_PATH`,
-and :variable:`CMAKE_FIND_USE_SYSTEM_ENVIRONMENT_PATH` variables.
+:variable:`CMAKE_FIND_USE_SYSTEM_ENVIRONMENT_PATH`,
+and :variable:`CMAKE_FIND_USE_PACKAGE_REGISTRY` variables.

Help/variable/CMAKE_FIND_USE_SYSTEM_ENVIRONMENT_PATH.rst

@@ -14,4 +14,5 @@ commands take precedence over this variable.
 See also the :variable:`CMAKE_FIND_USE_CMAKE_PATH`,
 :variable:`CMAKE_FIND_USE_CMAKE_ENVIRONMENT_PATH`,
 :variable:`CMAKE_FIND_USE_CMAKE_SYSTEM_PATH`,
+:variable:`CMAKE_FIND_USE_PACKAGE_REGISTRY`,
 and :variable:`CMAKE_FIND_USE_PACKAGE_ROOT_PATH` variables.

Source/cmFindPackageCommand.cxx

@@ -188,7 +188,12 @@ bool cmFindPackageCommand::InitialPass(std::vector<std::string> const& args,
   }
 
   // Check if User Package Registry should be disabled
-  if (this->Makefile->IsOn("CMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY")) {
+  // The `CMAKE_FIND_USE_PACKAGE_REGISTRY` has
+  // priority over the deprecated CMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY
+  if (const char* def =
+        this->Makefile->GetDefinition("CMAKE_FIND_USE_PACKAGE_REGISTRY")) {
+    this->NoUserRegistry = !cmSystemTools::IsOn(def);
+  } else if (this->Makefile->IsOn("CMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY")) {
     this->NoUserRegistry = true;
   }
 

Tests/FindPackageTest/CMakeLists.txt

@@ -391,16 +391,44 @@ try_compile(EXPORTER_COMPILED
 message(STATUS "Searching for export(PACKAGE) test project")
 set(CMakeTestExportPackage_DIR "" CACHE FILEPATH
   "Wipe out find results for testing." FORCE)
+
+message(STATUS "Searching for export(PACKAGE) with CMAKE_FIND_USE_PACKAGE_REGISTRY=TRUE")
+set(CMAKE_FIND_USE_PACKAGE_REGISTRY TRUE)
+find_package(CMakeTestExportPackage 1.${version} EXACT REQUIRED)
+if(NOT CMakeTestExportPackage_FOUND)
+  message(SEND_ERROR "CMakeTestExportPackage should be FOUND!")
+endif()
+unset(CMAKE_FIND_USE_PACKAGE_REGISTRY)
+
+message(STATUS "Searching for export(PACKAGE) with CMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY=FALSE")
+set(CMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY FALSE)
 find_package(CMakeTestExportPackage 1.${version} EXACT REQUIRED)
+if(NOT CMakeTestExportPackage_FOUND)
+  message(SEND_ERROR "CMakeTestExportPackage should be FOUND!")
+endif()
+unset(CMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY)
 
-message(STATUS "Searching for export(PACKAGE) test project with CMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY=TRUE")
+message(STATUS "Searching for export(PACKAGE) with CMAKE_FIND_USE_PACKAGE_REGISTRY=TRUE and CMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY=TRUE")
+set(CMAKE_FIND_USE_PACKAGE_REGISTRY TRUE)
 set(CMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY TRUE)
+set(CMakeTestExportPackage_DIR FALSE)
+find_package(CMakeTestExportPackage 1.${version} EXACT REQUIRED)
+if(NOT CMakeTestExportPackage_FOUND)
+  message(SEND_ERROR "CMakeTestExportPackage should be FOUND!")
+endif()
+unset(CMAKE_FIND_USE_PACKAGE_REGISTRY)
+unset(CMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY)
+
+message(STATUS "Searching for export(PACKAGE) with CMAKE_FIND_USE_PACKAGE_REGISTRY=FALSE and CMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY=FALSE")
+set(CMAKE_FIND_USE_PACKAGE_REGISTRY FALSE)
+set(CMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY FALSE)
 set(CMakeTestExportPackage_DIR "" CACHE FILEPATH
   "Wipe out find results for testing." FORCE)
-find_package(CMakeTestExportPackage  1.${version} EXACT QUIET)
+find_package(CMakeTestExportPackage 1.${version} EXACT QUIET)
 if(CMakeTestExportPackage_FOUND)
-  message(SEND_ERROR "CMakeTestExportPackage should not be FOUND!")
+  message(SEND_ERROR "CMakeTestExportPackage should be not FOUND!")
 endif()
+unset(CMAKE_FIND_USE_PACKAGE_REGISTRY)
 unset(CMAKE_FIND_PACKAGE_NO_PACKAGE_REGISTRY)
 
 message(STATUS "Remove export(PACKAGE) test project")