`clang-tidy` fails on CXX modules

[LecrisUT]

I don't know where the issue is coming from, so I am posting it here too. There is an equivalent discourse on CMake.

Error:

error: unable to handle compilation, expected exactly one compiler job in '' [clang-diagnostic-error]
warning: /clang-tidy-issue/test_module.ixx: 'linker' input unused [clang-diagnostic-unused-command-line-argument]
Found compiler error(s).

MWE:

# CMakeLists.txt
cmake_minimum_required(VERSION 3.26)
project(clang-tidy-issue
		LANGUAGES CXX)

set(CMAKE_CXX_STANDARD 20)
set(CMAKE_EXPERIMENTAL_CXX_MODULE_CMAKE_API 2182bf5c-ef0d-489a-91da-49dbc3090d2a)
set(CMAKE_EXPERIMENTAL_CXX_MODULE_DYNDEP TRUE)
set(CMAKE_CXX_EXTENSIONS OFF)
set(CMAKE_EXPERIMENTAL_CXX_MODULE_MAP_FORMAT clang)
set(CMAKE_CXX_CLANG_TIDY "clang-tidy;-checks=*")

add_library(test_library)
target_sources(test_library PUBLIC
		FILE_SET cxx_modules
		TYPE CXX_MODULES
		FILES
		test_module.ixx
		)

// test_module.ixx
module;

#include <string>

export module test_module;

export namespace test_module {
	consteval std::string_view version(){
		return "0.0.0";
	}
}

[llvmbot]

@llvm/issue-subscribers-clang-tidy

[LecrisUT]

So the issue here was that .ixx format was not being picked up. I have tested the current main branch that has 5b37cdd setting ImplementationFileExtensions: ['ixx'], but this issue persists.

[LecrisUT]

@carlosgalvezp @EugeneZelenko I thought that this issue would be related to the global option in #61947, but in my experimentation, this is not solved when set as a global option, and in fact it does not appear to have any effect on this issue (removing cxx, etc. still runs clang-tidy normally). Could you please take a look at this or assign it to someone to investigate this?

[carlosgalvezp]

Hi! That global option is only used in a handful of checks, and it's only used to determine whether a diagnostic belongs to a source file or a header file. Your error happens way before any of that. Since you are getting a Clang error (clang-diagnostic-error) I believe it makes sense for the Clang folks to take a look.

To clarify - are you able to compile the code with Clang (i.e. skipping clang-tidy)?

[llvmbot]

@llvm/issue-subscribers-clang-frontend

[LecrisUT]

To clarify - are you able to compile the code with Clang (i.e. skipping clang-tidy)?

Yes, the code compiles just fine using cmake+ninja+clang, independent of the extension used (i.e. .ixx works just fine), it's only clang-tidy that fails to detect anything outside .cxx, .cppm, etc. extensions.

Also this might be a related issue, but the following fails with clang-diagnostic-error even if I use .cppm extension:

\\ test_module.cppm
export module test_module;
export import :part;

\\ test_module_part.cppm
module;
#include <string>
export module test_module:part;

export namespace test_module {
	consteval std::string_view version() {
		return "0.0.0";
	}
}// namespace test_module

With the same cmake file as above, but including the test_module_part.cppm file. (The compilation works just fine, just clang-tidy complains of: error: module 'test_module:part' not found [clang-diagnostic-error])

[zurrutik]

Are there any new developments regarding this?

[ChuanqiXu9]

Are there any new developments regarding this?

In practice, we run clang-tidy after build so that clang-tidy can find them.