From 771a4000079a36c99ab8d1bc9bd2de12187b0961 Mon Sep 17 00:00:00 2001
From: Frank Dischner <frank.dischner@gmail.com>
Date: Wed, 26 Jan 2022 18:18:51 -0600
Subject: [PATCH] build: add support for AppleClang compiler

---
 CMakeLists.txt                   |  2 +-
 conanfile.py                     | 13 +++++++++++--
 src/cmake/CheckLibcxxInUse.cmake |  2 +-
 src/core/CMakeLists.txt          |  2 +-
 src/mp-unitsConfig.cmake         |  4 ++--
 5 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1e3ac12c..21bf11b0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -55,7 +55,7 @@ if(${projectPrefix}IWYU)
         MAX_LINE_LENGTH 120
         NO_COMMENTS
     )
-    if(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+    if(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
         set(${projectPrefix}AS_SYSTEM_HEADERS ON)
     endif()
 endif()
diff --git a/conanfile.py b/conanfile.py
index 7bddf441..2074d1aa 100644
--- a/conanfile.py
+++ b/conanfile.py
@@ -70,6 +70,12 @@ class UnitsConan(ConanFile):
             (compiler == "msvc" and (version == "19.3" or version >= "19.30") and compiler.cppstd == 23)
         return not std_support
 
+    @property
+    def _use_range_v3(self):
+        compiler = self.settings.compiler
+        version = Version(self.settings.compiler.version)
+        return ("clang" in compiler and compiler.libcxx == "libc++" and version < "14.0")
+
     def set_version(self):
         content = tools.load(os.path.join(self.recipe_folder, "src/CMakeLists.txt"))
         version = re.search(r"project\([^\)]+VERSION (\d+\.\d+\.\d+)[^\)]*\)", content).group(1)
@@ -81,7 +87,7 @@ class UnitsConan(ConanFile):
         if self._use_libfmt:
             self.requires("fmt/8.0.1")
 
-        if compiler == "clang" and compiler.libcxx == "libc++" and version < "14.0":
+        if self._use_range_v3:
             self.requires("range-v3/0.11.0")
 
     def build_requirements(self):
@@ -100,6 +106,9 @@ class UnitsConan(ConanFile):
         elif compiler == "clang":
             if version < "12":
                 raise ConanInvalidConfiguration("mp-units requires at least clang++-12")
+        elif compiler == "apple-clang":
+            if version < "13":
+                raise ConanInvalidConfiguration("mp-units requires at least AppleClang 13")
         elif compiler == "Visual Studio":
             if version < "16":
                 raise ConanInvalidConfiguration("mp-units requires at least Visual Studio 16.9")
@@ -148,7 +157,7 @@ class UnitsConan(ConanFile):
         self.cpp_info.components["core"].requires = ["gsl-lite::gsl-lite"]
         if compiler == "Visual Studio":
             self.cpp_info.components["core"].cxxflags = ["/utf-8"]
-        elif compiler == "clang" and compiler.libcxx == "libc++":
+        if self._use_range_v3:
             self.cpp_info.components["core"].requires.append("range-v3::range-v3")
 
         # rest
diff --git a/src/cmake/CheckLibcxxInUse.cmake b/src/cmake/CheckLibcxxInUse.cmake
index 4e122acf..7335da5c 100644
--- a/src/cmake/CheckLibcxxInUse.cmake
+++ b/src/cmake/CheckLibcxxInUse.cmake
@@ -23,7 +23,7 @@
 cmake_minimum_required(VERSION 3.15)
 
 function(check_libcxx_in_use variable)
-    if(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+    if(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
         message(CHECK_START "Checking if libc++ is being used")
         list(APPEND CMAKE_MESSAGE_INDENT "  ")
 
diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
index 25730a63..31900e53 100644
--- a/src/core/CMakeLists.txt
+++ b/src/core/CMakeLists.txt
@@ -44,7 +44,7 @@ target_include_directories(mp-units-core ${unitsAsSystem} INTERFACE
     $<INSTALL_INTERFACE:include>
 )
 
-if(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+if(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
     if(${projectPrefix}LIBCXX AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS "14")
         find_package(range-v3 CONFIG REQUIRED)
         target_link_libraries(mp-units-core INTERFACE range-v3::range-v3)
diff --git a/src/mp-unitsConfig.cmake b/src/mp-unitsConfig.cmake
index afe3f7a1..8b63a787 100644
--- a/src/mp-unitsConfig.cmake
+++ b/src/mp-unitsConfig.cmake
@@ -21,7 +21,7 @@
 # SOFTWARE.
 
 function(__check_libcxx_in_use variable)
-    if(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+    if(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
         message(CHECK_START "Checking if libc++ is being used")
         list(APPEND CMAKE_MESSAGE_INDENT "  ")
 
@@ -43,7 +43,7 @@ find_dependency(fmt)
 find_dependency(gsl-lite)
 
 # add range-v3 dependency only for clang + libc++
-if(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+if(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
     __check_libcxx_in_use(__units_libcxx)
     if(__units_libcxx AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS "14")
         find_dependency(range-v3)