Add CONAN_DOWNLOAD and CONAN_ISOLATE_HOME options

conan_provider.cmake

@@ -20,7 +20,14 @@
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 # SOFTWARE.
 
-set(CONAN_MINIMUM_VERSION 2.0.5)
+# Configurable variables
+set(CONAN_MINIMUM_VERSION "2.0.5" CACHE STRING "Minimum required Conan version")
+set(CONAN_HOST_PROFILE "default;auto-cmake" CACHE STRING "Conan host profile")
+set(CONAN_BUILD_PROFILE "default" CACHE STRING "Conan build profile")
+set(CONAN_INSTALL_ARGS "--build=missing" CACHE STRING "Command line arguments for conan install")
+set(CONAN_DOWNLOAD "if-missing" CACHE STRING "Download the Conan client (always, if-missing or never)")
+set(CONAN_DOWNLOAD_VERSION "latest" CACHE STRING "Download a specific Conan version")
+set(CONAN_ISOLATE_HOME "if-downloaded" CACHE STRING "Set $CONAN_HOME to \${CMAKE_BINARY_DIR}/conan_home (always, if-downloaded or never)")
 
 # Create a new policy scope and set the minimum required cmake version so the
 # features behind a policy setting like if(... IN_LIST ...) behaves as expected
@@ -445,7 +452,7 @@ function(conan_install)
     set(CONAN_OUTPUT_FOLDER ${CMAKE_BINARY_DIR}/conan)
     # Invoke "conan install" with the provided arguments
     set(CONAN_ARGS ${CONAN_ARGS} -of=${CONAN_OUTPUT_FOLDER})
-    message(STATUS "CMake-Conan: conan install ${CMAKE_SOURCE_DIR} ${CONAN_ARGS} ${ARGN}")
+    message(STATUS "CMake-Conan: ${CONAN_COMMAND} install ${CMAKE_SOURCE_DIR} ${CONAN_ARGS} ${ARGN}")
 
 
     # In case there was not a valid cmake executable in the PATH, we inject the
@@ -506,7 +513,7 @@ endfunction()
 
 function(conan_version_check)
     set(options )
-    set(oneValueArgs MINIMUM CURRENT)
+    set(oneValueArgs MINIMUM CURRENT RESULT)
     set(multiValueArgs )
     cmake_parse_arguments(CONAN_VERSION_CHECK
         "${options}" "${oneValueArgs}" "${multiValueArgs}" ${ARGN})
@@ -519,7 +526,19 @@ function(conan_version_check)
     endif()
 
     if(CONAN_VERSION_CHECK_CURRENT VERSION_LESS CONAN_VERSION_CHECK_MINIMUM)
-        message(FATAL_ERROR "CMake-Conan: Conan version must be ${CONAN_VERSION_CHECK_MINIMUM} or later")
+        if(CONAN_VERSION_CHECK_RESULT)
+            set(${CONAN_VERSION_CHECK_RESULT} FALSE PARENT_SCOPE)
+        endif()
+        if(CONAN_DOWNLOAD STREQUAL "if-missing")
+            message(STATUS "CMake-Conan: Found Conan but its version (${CONAN_VERSION_CHECK_CURRENT}) is older than "
+                           "required (${CONAN_VERSION_CHECK_MINIMUM}). Will download the latest version instead.")
+        else()
+            message(FATAL_ERROR "CMake-Conan: Conan version must be ${CONAN_VERSION_CHECK_MINIMUM} or later")
+        endif()
+    else()
+        if(CONAN_VERSION_CHECK_RESULT)
+            set(${CONAN_VERSION_CHECK_RESULT} TRUE PARENT_SCOPE)
+        endif()
     endif()
 endfunction()
 
@@ -573,7 +592,7 @@ function(download_conan)
     set(CONAN_FILE "conan-${CONAN_VERSION}-${HOST_OS}-${HOST_ARCH}.${FILE_EXT}")
     set(CONAN_URL "https://github.com/conan-io/conan/releases/download/${CONAN_VERSION}/${CONAN_FILE}")
 
-    message(STATUS "Downloading Conan ${CONAN_VERSION} from ${CONAN_URL}")
+    message(STATUS "CMake-Conan: Downloading Conan ${CONAN_VERSION} from ${CONAN_URL}")
     include(FetchContent)
     FetchContent_Declare(
         Conan
@@ -608,9 +627,37 @@ macro(conan_provide_dependency method package_name)
     set_property(GLOBAL PROPERTY CONAN_PROVIDE_DEPENDENCY_INVOKED TRUE)
     get_property(_conan_install_success GLOBAL PROPERTY CONAN_INSTALL_SUCCESS)
     if(NOT _conan_install_success)
-        find_program(CONAN_COMMAND "conan" REQUIRED)
-        conan_get_version(${CONAN_COMMAND} CONAN_CURRENT_VERSION)
-        conan_version_check(MINIMUM ${CONAN_MINIMUM_VERSION} CURRENT ${CONAN_CURRENT_VERSION})
+        if(NOT CONAN_DOWNLOAD STREQUAL "always")
+            find_program(CONAN_COMMAND "conan" QUIET)
+            if(CONAN_COMMAND)
+                conan_get_version(${CONAN_COMMAND} CONAN_CURRENT_VERSION)
+                conan_version_check(MINIMUM ${CONAN_MINIMUM_VERSION} CURRENT ${CONAN_CURRENT_VERSION}
+                                    RESULT _conan_version_check_result)
+                if(NOT _conan_version_check_result)
+                    set(CONAN_COMMAND "-NOTFOUND")
+                endif()
+            endif()
+        endif()
+        if(NOT CONAN_COMMAND)
+            if(CONAN_DOWNLOAD STREQUAL "never")
+                message(FATAL_ERROR "CMake-Conan: Conan executable not found. "
+                                    "Please install Conan, set CONAN_COMMAND or enable CONAN_DOWNLOAD")
+            endif()
+            if(CONAN_DOWNLOAD_VERSION STREQUAL "latest")
+                get_latest_conan_version(_download_version)
+            else()
+                set(_download_version ${CONAN_DOWNLOAD_VERSION})
+            endif()
+            download_conan(VERSION ${_download_version} DESTINATION "${CMAKE_BINARY_DIR}/conan_client")
+            set(CONAN_COMMAND "${CMAKE_BINARY_DIR}/conan_client/conan")
+            set(_conan_downloaded TRUE)
+        endif()
+
+        if(CONAN_ISOLATE_HOME STREQUAL "always" OR (CONAN_ISOLATE_HOME STREQUAL "if-downloaded" AND _conan_downloaded))
+            message(STATUS "CMake-Conan: Setting CONAN_HOME to '${CMAKE_BINARY_DIR}/conan_home'")
+            set(ENV{CONAN_HOME} "${CMAKE_BINARY_DIR}/conan_home")
+        endif()
+
         message(STATUS "CMake-Conan: first find_package() found. Installing dependencies with Conan")
         if("default" IN_LIST CONAN_HOST_PROFILE OR "default" IN_LIST CONAN_BUILD_PROFILE)
             conan_profile_detect_default()
@@ -711,11 +758,6 @@ endmacro()
 # to check if the dependency provider was invoked at all.
 cmake_language(DEFER DIRECTORY "${CMAKE_SOURCE_DIR}" CALL conan_provide_dependency_check)
 
-# Configurable variables for Conan profiles
-set(CONAN_HOST_PROFILE "default;auto-cmake" CACHE STRING "Conan host profile")
-set(CONAN_BUILD_PROFILE "default" CACHE STRING "Conan build profile")
-set(CONAN_INSTALL_ARGS "--build=missing" CACHE STRING "Command line arguments for conan install")
-
 find_program(_cmake_program NAMES cmake NO_PACKAGE_ROOT_PATH NO_CMAKE_PATH NO_CMAKE_ENVIRONMENT_PATH NO_CMAKE_SYSTEM_PATH NO_CMAKE_FIND_ROOT_PATH)
 if(NOT _cmake_program)
     get_filename_component(PATH_TO_CMAKE_BIN "${CMAKE_COMMAND}" DIRECTORY)

tests/resources/download/auto_download/CMakeLists.txt

@@ -0,0 +1,6 @@
+cmake_minimum_required(VERSION 3.24)
+project(MyApp CXX)
+
+find_package(hello REQUIRED)
+add_executable(app main.cpp)
+target_link_libraries(app hello::hello)

tests/resources/download/auto_download/conanfile.txt

@@ -0,0 +1,5 @@
+[requires]
+hello/0.1
+
+[generators]
+CMakeDeps

tests/resources/download/download_function/conanfile.txt

@@ -1,2 +1 @@
 [requires]
-hello/0.1

tests/resources/download/get_latest_version/conanfile.txt

@@ -1,2 +1 @@
 [requires]
-hello/0.1

tests/test_smoke.py

@@ -772,4 +772,79 @@ def test_download_function(self, capfd, basic_cmake_project):
         out, _ = capfd.readouterr()
         assert 'Downloading Conan ' in out
         assert (os.path.exists(os.path.join(binary_dir, 'conan', 'conan')) or
-                os.path.exists(os.path.join(binary_dir, 'conan', 'conan.exe')))
+                os.path.exists(os.path.join(binary_dir, 'conan', 'conan.exe')))
+
+    @staticmethod
+    def _prepare_isolated_home(binary_dir):
+        # Copy everything except settings.yml from the real CONAN_HOME to the expected isolated CONAN_HOME.
+        # The settings.yml should be re-created after CMake configure.
+        conan_home = os.getenv("CONAN_HOME")
+        isolated_home = os.path.join(binary_dir, "conan_home")
+        shutil.copytree(conan_home, isolated_home)
+        isolated_settings_yml = os.path.join(isolated_home, "settings.yml")
+        os.unlink(isolated_settings_yml)
+        return isolated_settings_yml
+
+    @pytest.mark.parametrize("isolate", ["always", "never"])
+    def test_isolate_home(self, capfd, basic_cmake_project, isolate):
+        "Test that CONAN_ISOLATE_HOME=always/never results in {build_dir}/conan_home being used / not used"
+        source_dir, binary_dir = basic_cmake_project
+        isolated_settings_yml = self._prepare_isolated_home(binary_dir)
+        assert not os.path.exists(isolated_settings_yml)
+        shutil.copytree(src_dir / 'tests' / 'resources' / 'download' / 'auto_download', source_dir, dirs_exist_ok=True)
+        run(f'cmake -S {source_dir} -B {binary_dir} -DCMAKE_PROJECT_TOP_LEVEL_INCLUDES={conan_provider} -DCMAKE_BUILD_TYPE=Release'
+            f' -DCONAN_ISOLATE_HOME={isolate}')
+        out, _ = capfd.readouterr()
+        if isolate == "always":
+            assert 'Setting CONAN_HOME to ' in out
+            assert os.path.exists(isolated_settings_yml)
+        else:
+            assert 'Setting CONAN_HOME to ' not in out
+            assert not os.path.exists(isolated_settings_yml)
+
+    @pytest.mark.parametrize("conan_missing", [True, False])
+    def test_download_never(self, capfd, basic_cmake_project, conan_missing):
+        source_dir, binary_dir = basic_cmake_project
+        shutil.copytree(src_dir / 'tests' / 'resources' / 'download' / 'auto_download', source_dir, dirs_exist_ok=True)
+        run(f'cmake -S {source_dir} -B {binary_dir} -DCMAKE_PROJECT_TOP_LEVEL_INCLUDES={conan_provider} -DCMAKE_BUILD_TYPE=Release'
+            ' -DCONAN_DOWNLOAD=never' + (' -DCONAN_MINIMUM_VERSION=100.0.0' if conan_missing else ''), check=False)
+        out, err = capfd.readouterr()
+        assert 'Downloading Conan ' not in out
+        if conan_missing:
+            assert 'CMake-Conan: Conan version must be 100.0.0 or later' in err
+        else:
+            assert 'CMake-Conan: Conan version must be 100.0.0 or later' not in err
+
+    def test_download_always(self, capfd, basic_cmake_project):
+        source_dir, binary_dir = basic_cmake_project
+        isolated_settings_yml = self._prepare_isolated_home(binary_dir)
+        assert not os.path.exists(isolated_settings_yml)
+        shutil.copytree(src_dir / 'tests' / 'resources' / 'download' / 'auto_download', source_dir, dirs_exist_ok=True)
+        run(f'cmake -S {source_dir} -B {binary_dir} -DCMAKE_PROJECT_TOP_LEVEL_INCLUDES={conan_provider} -DCMAKE_BUILD_TYPE=Release'
+            ' -DCONAN_DOWNLOAD=always -DCONAN_ISOLATE_HOME=if-downloaded -DCONAN_MINIMUM_VERSION=100.0.0', check=False)
+        out, _ = capfd.readouterr()
+        assert 'Downloading Conan ' in out
+        assert 'Setting CONAN_HOME to ' in out
+        assert os.path.exists(isolated_settings_yml)
+        assert (os.path.exists(os.path.join(binary_dir, 'conan_client', 'conan')) or
+                os.path.exists(os.path.join(binary_dir, 'conan_client', 'conan.exe')))
+
+    @pytest.mark.parametrize("conan_missing", [True, False])
+    def test_download_if_missing(self, capfd, basic_cmake_project, conan_missing):
+        source_dir, binary_dir = basic_cmake_project
+        print(binary_dir)
+        shutil.copytree(src_dir / 'tests' / 'resources' / 'download' / 'auto_download', source_dir, dirs_exist_ok=True)
+        run(f'cmake -S {source_dir} -B {binary_dir} -DCMAKE_PROJECT_TOP_LEVEL_INCLUDES={conan_provider} -DCMAKE_BUILD_TYPE=Release'
+            ' -DCONAN_DOWNLOAD=if-missing -DCONAN_ISOLATE_HOME=never' + (' -DCONAN_MINIMUM_VERSION=100.0.0' if conan_missing else ''))
+        out, err = capfd.readouterr()
+        assert 'CMake-Conan: Conan version must be 100.0.0 or later' not in err
+        assert not os.path.exists(os.path.join(binary_dir, 'conan_home'))
+        if conan_missing:
+            assert 'Will download the latest version instead.' in out
+            assert 'Downloading Conan ' in out
+            assert re.search(r"conan_client/conan(\.exe)? install ", out)
+            assert (os.path.exists(os.path.join(binary_dir, 'conan_client', 'conan')) or
+                    os.path.exists(os.path.join(binary_dir, 'conan_client', 'conan.exe')))
+        else:
+            assert 'Will download the latest version instead.' not in out
+            assert 'Downloading Conan ' not in out