<module>-Swift.h: fatal error: module '<module>' not found

[vakhidbetrakhmadov]

Hello,

I am trying to compile a mixed_language_library target that depends on a swift_library target that exports Objective-C APIs.

I am getting the following error: <module>-Swift.h: fatal error: module '<module>' not found.

I have created a minimal repro example: mixed-language-cannot-find-module-repro.

To observe the error run: bazelisk build -s --sandbox_debug --platforms=@build_bazel_apple_support//platforms:ios_sim_arm64 //examples/apple/mixed_language_cannot_find_module_repro:Consumer.

[vakhidbetrakhmadov]

#1174 might be the same issue

[vakhidbetrakhmadov]

As far as i understand, generated <module>-Swift.h files always use @import <module>, and in order for an @import <module> to work there must be a corresponding -fmodule-map-file=path_to_<module>.modulemap flag being passed when compiling a .m file that imports <module>-Swift.h , which currently doesn't happen.

Previously i used apple_framework,and it worked if my understanding is correct because -F<framework_search_dir> containing <module>.framework containing module.modulemap was passed when compiling a .m that imports <module>-Swift.h.

[vakhidbetrakhmadov]

If i copy the failed compile command from the logs, add -fmodule-map-file=path_to_<module>.modulemap and run, it succeeds.

[vakhidbetrakhmadov]

Using --features=swift.propagate_generated_module_map fixes the issue.
Thanks to @brentleyjones for suggestion 🙏