Adds function for getting enabled languages (#136)

* adds function for getting enabled languages

* suggested review changes

Author: ryanmrichard

cmake/cmakepp_lang/cmakepp_lang.cmake

@@ -24,6 +24,7 @@ include_guard()
 include(cmakepp_lang/algorithm/algorithm)
 include(cmakepp_lang/asserts/asserts)
 include(cmakepp_lang/class/class)
+include(cmakepp_lang/detection/detection)
 include(cmakepp_lang/exceptions/exceptions)
 include(cmakepp_lang/map/map)
 include(cmakepp_lang/object/object)

cmake/cmakepp_lang/detection/detection.cmake

@@ -0,0 +1,20 @@
+# Copyright 2025 CMakePP
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+#[[[ @module
+# Provides functions for detecting the state of CMake and/or the runtime.
+#]]
+
+include_guard()
+include(cmakepp_lang/detection/languages)

cmake/cmakepp_lang/detection/languages.cmake

@@ -0,0 +1,48 @@
+# Copyright 2025 CMakePP
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+include_guard()
+include(cmakepp_lang/utilities/return)
+
+#[[[
+# Wraps the process of retrieving a list of enabled languages.
+#
+# CMake sets a global property
+# :ref:`ENABLED_LANGUAGES <https://cmake.org/cmake/help/latest/prop_gbl/ENABLED_LANGUAGES.html>` 
+# to be a list of coding
+# languages which have been enabled either via 
+# :ref:`project() <https://cmake.org/cmake/help/latest/command/project.html>` or 
+# the
+# :ref:`enable_language() <https://cmake.org/cmake/help/latest/command/enable_language.html>` 
+# commands. CMake's documentation is a bit dodgy in 
+# discussing what variables the aforementioned commands set, so we wrote this
+# function as a wrapper around the logic in the event that CMake changes how
+# they do things. At the very least, this function should be more user-
+# friendly.
+#
+# :param: return_variable A variable to hold the resulting list.
+# :type: list*
+#]]
+function(cpp_enabled_languages _el_return_variable)
+    get_property("${_el_return_variable}" GLOBAL PROPERTY ENABLED_LANGUAGES)
+
+    # CMake apparently doesn't remove NONE from the list if other languages are
+    # also in the list...
+    list(LENGTH "${_el_return_variable}" _el_length)
+    if("${_el_length}" GREATER 1)
+        list(REMOVE_ITEM "${_el_return_variable}" "NONE")
+    endif()
+
+    cpp_return("${_el_return_variable}")
+endfunction()

tests/CMakeLists.txt

@@ -20,14 +20,15 @@ FetchContent_Declare(
 set(build_testing_old "${BUILD_TESTING}")
 set(BUILD_TESTING OFF CACHE BOOL "" FORCE)
 FetchContent_MakeAvailable(cmake_test)
+
 include(cmake_test/cmake_test)
 
 set(BUILD_TESTING "${build_testing_old}" CACHE BOOL "" FORCE)
 
-
 ct_add_dir(algorithm)
 ct_add_dir(asserts)
 ct_add_dir(class)
+ct_add_dir(detection)
 ct_add_dir(docs)
 ct_add_dir(examples)
 ct_add_dir(exceptions)

tests/detection/languages.cmake

@@ -0,0 +1,19 @@
+ct_add_test(NAME test_cpp_enabled_languages)
+function(${test_cpp_enabled_languages})
+    include(cmakepp_lang/detection/languages)
+
+    #cpp_enabled_languages(the_languages)
+    #set(correct "NONE")
+    #ct_assert_equal(the_languages "${correct}")
+
+    enable_language(C)
+    cpp_enabled_languages(the_languages)
+    set(correct "C")
+    ct_assert_equal(the_languages "${correct}")
+
+    enable_language(CXX)
+    cpp_enabled_languages(the_languages)
+    set(correct "C" "CXX")
+    ct_assert_equal(the_languages "${correct}")
+endfunction()
+