Toolchain declare DIR find package variables

conan/tools/cmake/cmakedeps/templates/__init__.py

@@ -1,6 +1,7 @@
 import jinja2
 from jinja2 import Template
 
+from conan.tools.cmake.utils import get_file_name
 from conans.errors import ConanException
 
 
@@ -86,13 +87,6 @@ def get_target_namespace(req):
     return ret or req.ref.name
 
 
-def get_file_name(req):
-    ret = req.new_cpp_info.get_property("cmake_file_name", "CMakeDeps")
-    if not ret:
-        ret = req.cpp_info.get_filename("cmake_find_package_multi", default_name=False)
-    return ret or req.ref.name
-
-
 def get_component_alias(req, comp_name):
     if comp_name not in req.new_cpp_info.components:
         # foo::foo might be referencing the root cppinfo

conan/tools/cmake/cmakedeps/templates/target_data.py

@@ -2,7 +2,8 @@
 import textwrap
 
 from conan.tools.cmake.cmakedeps.templates import CMakeDepsFileTemplate, get_component_alias, \
-    get_file_name, get_target_namespace
+    get_target_namespace
+from conan.tools.cmake.utils import get_file_name
 
 """
 

conan/tools/cmake/toolchain.py

@@ -9,7 +9,7 @@
 
 from conan.tools import CONAN_TOOLCHAIN_ARGS_FILE
 from conan.tools._compilers import architecture_flag, use_win_mingw
-from conan.tools.cmake.utils import is_multi_configuration
+from conan.tools.cmake.utils import is_multi_configuration, get_file_name
 from conan.tools.microsoft.toolchain import write_conanvcvars, vs_ide_version
 from conans.errors import ConanException
 from conans.util.files import load, save
@@ -383,6 +383,12 @@ class FindConfigFiles(Block):
         {% if android_prefix_path %}
         set(CMAKE_FIND_ROOT_PATH {{ android_prefix_path }} ${CMAKE_FIND_ROOT_PATH})
         {% endif %}
+
+        # To support cross building to iOS, watchOS and tvOS where CMake looks for config files
+        # only in the system frameworks unless you declare the XXX_DIR variables
+        {% for name in find_names %}
+        set({{ name }}_DIR "{{ generators_folder }}")
+        {% endfor %}
         """)
 
     def context(self):
@@ -395,10 +401,17 @@ def context(self):
 
         os_ = self._conanfile.settings.get_safe("os")
         android_prefix = "${CMAKE_CURRENT_LIST_DIR}" if os_ == "Android" else None
+
+        host_req = self._conanfile.dependencies.transitive_host_requires
+        find_names_needed = os_ in ('iOS', "watchOS", "tvOS")
+        find_names = [get_file_name(req) for req in host_req] if find_names_needed else []
+
         return {"find_package_prefer_config": find_package_prefer_config,
                 "cmake_prefix_path": "${CMAKE_CURRENT_LIST_DIR}",
                 "cmake_module_path": "${CMAKE_CURRENT_LIST_DIR}",
-                "android_prefix_path": android_prefix}
+                "android_prefix_path": android_prefix,
+                "find_names": find_names,
+                "generators_folder": "${CMAKE_CURRENT_LIST_DIR}"}
 
 
 class UserToolchain(Block):

conan/tools/cmake/utils.py

@@ -2,3 +2,14 @@ def is_multi_configuration(generator):
     if not generator:
         return False
     return "Visual" in generator or "Xcode" in generator or "Multi-Config" in generator
+
+
+def get_file_name(conanfile):
+    """Get the name of the file for the find_package(XXX)"""
+    # This is used by the CMakeToolchain to adjust the XXX_DIR variables and the CMakeDeps. Both
+    # to know the file name that will have the XXX-config.cmake files.
+    ret = conanfile.new_cpp_info.get_property("cmake_file_name", "CMakeDeps")
+    if not ret:
+        ret = conanfile.cpp_info.get_filename("cmake_find_package_multi", default_name=False)
+    return ret or conanfile.ref.name
+

conans/test/functional/toolchains/cmake/cmakedeps/test_apple_frameworks.py

@@ -193,17 +193,10 @@ class HELLO_EXPORT Hello
 def test_apple_own_framework_cross_build(settings):
     client = TestClient()
 
-    # FIXME: The crossbuild for iOS etc is failing with find_package because cmake ignore the
-    #        cmake_prefix_path to point only to the Frameworks of the system. The only fix found
-    #        would require to introduce something like "set (mylibrary_DIR "${CMAKE_BINARY_DIR}")"
-    #        at the toolchain (but it would require the toolchain to know about the deps)
-    #        https://stackoverflow.com/questions/65494246/cmakes-find-package-ignores-the-paths-option-when-building-for-ios#
     test_cmake = textwrap.dedent("""
         cmake_minimum_required(VERSION 3.15)
         project(Testing CXX)
-        # set(CMAKE_FIND_DEBUG_MODE TRUE)
 
-        set (mylibrary_DIR "${CMAKE_BINARY_DIR}")
         find_package(mylibrary REQUIRED)
 
         add_executable(timer timer.cpp)

conans/test/unittests/tools/cmake/test_cmaketoolchain.py

@@ -24,6 +24,8 @@ def conanfile():
     c.settings.compiler.libcxx = "libstdc++"
     c.conf = Conf()
     c.folders.set_base_generators(".")
+    c._conan_node = Mock()
+    c._conan_node.dependencies = []
     return c