Conditional settings, options and requirements

Remember, in your conanfile.py you have also access to the options of your dependencies, and you can use them to:

Add requirements dynamically
Change values of options

The configure method might be used to hardcode dependencies options values. It is strongly discouraged to use it to change the settings values, please remember that settings are a configuration input, so it doesn’t make sense to modify it in the recipes.

Also, for options, a more flexible solution is to define dependencies options values in the default_options, not in the configure() method, as this would allow to override them. Hardcoding them in the configure() method won’t allow that and thus won’t easily allow conflict resolution. Use it only when it is absolutely necessary that the package dependencies use those options.

Here is an example of what we could do in our configure method:

...
requires = "Poco/1.9.0@pocoproject/stable" # We will add OpenSSL dynamically "OpenSSL/1.0.2d@lasote/stable"
...

def configure(self):
    # We can control the options of our dependencies based on current options
    self.options["OpenSSL"].shared = self.options.shared

    # Maybe in windows we know that OpenSSL works better as shared (false)
    if self.settings.os == "Windows":
       self.options["OpenSSL"].shared = True

       # Or adjust any other available option
       self.options["Poco"].other_option = "foo"

    # We could check the presence of an option
    if "shared" in self.options:
        pass

def requirements(self):
    # Or add a new requirement!
    if self.options.testing:
       self.requires("OpenSSL/2.1@memsharded/testing")
    else:
       self.requires("OpenSSL/1.0.2d@lasote/stable")