How to implement conditional requirements in a conanfile?

Question

We have projects that require different Conan packages during unit tests (i.e. mocks) than during normal compilation. Is there a best practice how to implement conditional requirements in a conanfile for such a use case?

We have tried using switches with environment variables like this:

class project_a(ConanFile):
....
    def requirements()
        if os.getenv('UNIT_TESTING') == 'true':
            self.requires('mock_for_testing/1.0.0@someuser/somechannel
...

But then the requirements for project_a are always changed during unit testing. So also when a project is tested, that consumes project_a.

Answer 1

Conan is not focused on running unit test when building packages, it's focused on packaging artifacts like libraries, headers and binaries.

However, there is a prepared environment variable which can be used for unit tests: CONAN_RUN_TESTS. You should use tools.get_env instead.

Also, take a look on self.develop which can be used to detected when you are building or consuming a package, so you can use as condition to add or not a requirement:

def requirements()
    if self.develop:
        self.requires('mock/1.0.0@user/channel')

Then, the package will be consumed only when running the command create.