If defined in the environment, this variable will raise errors whenever a Conan 2.0 deprecated feature is used. It is a good mechanism to check the recipes future Conan 2.0 “compliance”. Activating it should not change behavior in any way, just raise error for deprecated things, but if it works, the same result should be achieved. The number of deprecated features will increase in future Conan 1.X releases, it could be a good practice to have it activated in some nightly job or the like, to report on current status of your recipes.

So, if you are ready to experiment add the variable CONAN_V2_MODE to your environment and, please, report your feedback about it.

The following is a current known list of features that will change in Conan 2.0 and might start raising errors if CONAN_V2_MODE is activated:

Changes in recipes

These changes could break existing recipes:

  • Forbid access to self.cpp_info in conanfile::package_id() method.

  • Deprecate conanfile::config() method.

  • Deprecate old python_requires syntax.

  • Forbid access to in conanfile.package().

  • default_options are required to be a dictionary.

  • Raise if setting cppstd appears in the recipe.

  • Forbid self.settings and self.options in conanfile::source() method.

  • Deprecate tools.msvc_build_command.

  • Deprecate tools.build_sln_command.

  • Deprecate cpp_info.cppflags (use cxxflags instead).

  • Deprecate environment variables CONAN_USERNAME and CONAN_CHANNEL.

  • PYTHONPATH is not added automatically to the environment before running consumer functions.

  • Attribute self.version is ensured to be a string in all the functions and scenarios.

  • Access to member name in deps_cpp_info objects is forbidden, use get_name(<generator>) with the name of the generator.

Changes in profiles

Could break existing profiles:

  • Deprecate scopes section in profiles.

Other changes

  • Package name used by the pkg_config generator uses the same rules as any other generator. Previously, if it was not explicit, it was using lowercase when it was different from the package name.

  • If build_type or compiler are not defined when using build helpers Conan will raise an error.

  • New compiler detection algorithm is used (e.g. when running conan profile new <name> --detect). Previously, <compiler> --version was parsed to detect the compiler and its version. Now, using CONAN_V2_MODE, Conan will try to detect the compiler and its version via compiler’s built-in macro definitions.


More changes will be added, some of them could be reverted and the behavior may change without further noticing. If you are using CONAN_V2_MODE, thanks! We really appreciate your feedback about the future of Conan.