Define compiler variables in CMakePresets.json (#16762)

* define compiler variables in CMakePresets.json

* fix test

---------

Co-authored-by: memsharded <james@conan.io>

conan/tools/cmake/presets.py

@@ -5,7 +5,7 @@
 
 from conan.api.output import ConanOutput, Color
 from conan.tools.cmake.layout import get_build_folder_custom_vars
-from conan.tools.cmake.toolchain.blocks import GenericSystemBlock
+from conan.tools.cmake.toolchain.blocks import GenericSystemBlock, CompilersBlock
 from conan.tools.cmake.utils import is_multi_configuration
 from conan.tools.build import build_jobs
 from conan.tools.microsoft import is_msvc
@@ -158,6 +158,13 @@ def _configure_preset(conanfile, generator, cache_variables, toolchain_file, mul
                     "strategy": "external"
                 }
 
+        # Set the compiler like in the toolchain. Some IDEs like VS or VSCode require the compiler
+        # being set to cl.exe in order to activate the environment using vcvarsall.bat according to
+        # the toolset and architecture settings.
+        compilers = CompilersBlock.get_compilers(conanfile)
+        for lang, compiler in compilers.items():
+            ret["cacheVariables"][f"CMAKE_{lang}_COMPILER"] = compiler.replace("\\", "/")
+
         ret["toolchainFile"] = toolchain_file
         if conanfile.build_folder:
             # If we are installing a ref: "conan install <ref>", we don't have build_folder, because

conan/tools/cmake/toolchain/blocks.py

@@ -852,9 +852,13 @@ class CompilersBlock(Block):
     """)
 
     def context(self):
+        return {"compilers": self.get_compilers(self._conanfile)}
+
+    @staticmethod
+    def get_compilers(conanfile):
         # Reading configuration from "tools.build:compiler_executables" -> {"C": "/usr/bin/gcc"}
-        compilers_by_conf = self._conanfile.conf.get("tools.build:compiler_executables", default={},
-                                                     check_type=dict)
+        compilers_by_conf = conanfile.conf.get("tools.build:compiler_executables", default={},
+                                               check_type=dict)
         # Map the possible languages
         compilers = {}
         # Allowed <LANG> variables (and <LANG>_LAUNCHER)
@@ -865,7 +869,7 @@ def context(self):
             # To set CMAKE_<LANG>_COMPILER
             if comp in compilers_by_conf:
                 compilers[lang] = compilers_by_conf[comp]
-        return {"compilers": compilers}
+        return compilers
 
 
 class GenericSystemBlock(Block):

test/integration/toolchains/cmake/test_cmaketoolchain.py

@@ -1046,6 +1046,30 @@ def test_set_cmake_lang_compilers_and_launchers():
     assert 'set(CMAKE_RC_COMPILER "C:/local/rc.exe")' in toolchain
 
 
+def test_cmake_presets_compiler():
+    profile = textwrap.dedent(r"""
+    [settings]
+    os=Windows
+    arch=x86_64
+    compiler=msvc
+    compiler.version=193
+    compiler.runtime=dynamic
+    [conf]
+    tools.build:compiler_executables={"c": "cl", "cpp": "cl.exe", "rc": "C:\\local\\rc.exe"}
+    """)
+    client = TestClient()
+    conanfile = GenConanfile().with_settings("os", "arch", "compiler")\
+        .with_generator("CMakeToolchain")
+    client.save({"conanfile.py": conanfile,
+                 "profile": profile})
+    client.run("install . -pr:b profile -pr:h profile")
+    presets = json.loads(client.load("CMakePresets.json"))
+    cache_variables = presets["configurePresets"][0]["cacheVariables"]
+    assert cache_variables["CMAKE_C_COMPILER"] == "cl"
+    assert cache_variables["CMAKE_CXX_COMPILER"] == "cl.exe"
+    assert cache_variables["CMAKE_RC_COMPILER"] == "C:/local/rc.exe"
+
+
 def test_cmake_layout_toolchain_folder():
     """ in single-config generators, the toolchain is a different file per configuration
     https://github.com/conan-io/conan/issues/12827