Incubating features¶

This section is dedicated to new features that are under development, looking for user testing and feedback. They are generally behind a flag to enable them to explicitly opt-in on this testing stage. They require the very latest Conan version (sometimes recommended running from the develop2 source branch), and explicitly setting those flags.

New CMakeConfigDeps generator¶

This generator is designed as a replacement of the current CMakeDeps generator, with multiple pending fixes and improvements that couldn’t easily be done in the current one without breaking:

Creates real SHARED/STATIC/INTERFACE IMPORTED targets, no more artificial interface targets. The CONAN_LIB:: and other similar targets do not exist anymore.
Defines IMPORTED_CONFIGURATIONS for targets.
CONFIG definition of dependencies matching the dependency Release/Debug/etc build_type, no longer using the consumer one.
Definition of IMPORTED_LOCATION and IMPORTED_IMPLIB for library targets.
Definition of LINK_LANGUAGES based on the recipe languages and cpp_info/component languages properties.
All these allows better propagation of linkage requirement and visibility, avoiding some linkage error of transitive shared libraries in Linux.
Better definition of requires relationships accross components inside the same package and with respect to other packages.
It doesn’t need any build_context_activated or build_context_suffix to use tool_requires dependencies.
Definition of cpp_info/component.exe information (should include the .location definition too), to define EXECUTABLE targets that can be run.
Executables from requires can also be used in non cross-build scenarios. When a tool_requires to the same depependency exists, then those executables will have priority.
Creation of a new conan_cmakedeps_paths.cmake that contains definitions of <pkg>_DIR paths for direct finding of the dependencies. This file is also planned to be used in cmake-conan to extend its usage and avoid some current limitations due to the fact that a CMake driven installation cannot inject a toolchain later.

Note

This generator is only intended to generate config.cmake config files, it will not generate Find*.cmake find modules, and support for it is not planned. Use the CMakeDeps generator for that.

The new fields that can be defined in the cpp_info or cpp_info.components, besides the already defined in CppInfo are:

# EXPERIMENTAL FIELDS, used exclusively by new CMakeConfigDeps (-c tools.cmake.cmakedeps:new)
self.cpp_info.type  # The type of this artifact "shared-library", "static-library", etc (same as package_type)
self.cpp_info.location # full location (path and filename with extension) of the artifact
self.cpp_info.link_location  # Location of the import library for Windows .lib associated to a dll
self.cpp_info.languages # same as "languages" attribute, it can be "C", "C++"
self.cpp_info.exe  # Definition of an executable artifact

These fields will be auto-deduced from the other cpp_info and components definitions, like the libs or libdirs fields, but the automatic deduction might have limitations. Defining them explicitly will inhibit the auto deduction and use the value as provided by the recipe.

This feature is enabled with the -c tools.cmake.cmakedeps:new=will_break_next configuration. The value will_break_next will change in next releases to emphasize the fact that this feature is not suitable for usage beyond testing. Just by enabling this conf and forcing the build of packages that use CMakeDeps will trigger the usage of the new generator.

This new generator will also be usable in conanfile files with:

conanfile.txt¶

[generators]
CMakeConfigDeps

conanfile.py¶

class Pkg(ConanFile):
   generators = "CMakeConfigDeps"

Or:

conanfile.py¶

from conan import ConanFile
from conan.tools.cmake import CMakeConfigDeps

class TestConan(ConanFile):

   def generate(self):
      deps = CMakeConfigDeps(self)
      deps.generate()

The -c tools.cmake.cmakedeps:new=will_break_next is still necessary for this recipe CMakeConfigDeps usage, if the config is not enabled, those recipes will fail. It is also possible to define -c tools.cmake.cmakedeps:new=recipe_will_break to enable exclusively the CMakeConfigDeps generators usages, but not the automatic replacement of existing CMakeDeps by the CMakeConfigDeps.

Note that the feature is still “incubating”, even for the explicit CMakeConfigDeps generator syntax, this recipe is subject to break or be removed at any time.

For any feedback, please open new tickets in https://github.com/conan-io/conan/issues. This feedback is very important to stabilize the feature and get it out of incubating, so even if it worked fine and you found no issue, having the positive feedback reported is very useful.

Workspaces¶

The workspaces feature can be enabled defining the environment variable CONAN_WORKSPACE_ENABLE=will_break_next. The value will_break_next is used to emphasize that it will change in next releases, and this feature is for testing only, it cannot be used in production.

Once the feature is enabled, workspaces are defined by the conanws.yml and/or conanws.py files. By default, any Conan command will traverse up the file system from the current working directory to the filesystem root, until it finds one of those files. That will define the “root” workspace folder.

The conan workspace command allows to open, add, remove packages from the current workspace. Check the conan workspace -h help and the help of the subcommands to check their usage.

Dependencies added to a workspace work as local editable dependencies. They are only resolved as editable under the current workspace, if the current directory is moved outside of it, those editable dependencies won’t be used anymore.

The paths in the conanws files are intended to be relative to be relocatable if necessary, or could be committed to Git in monorepo-like projects.

Workspace files syntax¶

The most basic implementation of a workspace is a conanws.yml file with just the definition of properties. For example, a very basic workspace file that just defines the current CONAN_HOME to be a local folder would be:

conanws.yml¶

home_folder: myhome

But a conanws.yml can be extended with a way more powerful conanws.py that follows the same relationship as a ConanFile does with its conandata.yml, for example, it can dynamically define the workspace home with:

conanws.py¶

from conan import Workspace

class MyWs(Workspace):

   def home_folder(self):
      # This reads the "conanws.yml" file, and returns "new_myhome"
      # as the current CONAN_HOME for this workspace
      return "new_" + self.conan_data["home_folder"]

So the command conan config home:

$ conan config home
/path/to/ws/new_myhome

Will display as the current CONAN_HOME the new_myhome folder (by default it is relative to the folder containing the conanws file)

Likewise, a workspace conanws.yml defining 2 editables could be:

conanws.yml¶

editables:
   dep1/0.1:
      path: dep1
   dep2/0.1:
      path: dep2

But if we wanted to dynamically define the editables, for example based on the existence of some name.txt and version.txt files in folders, the editables could be defined in conanws.py as:

conanws.py¶

import os
from conan import Workspace

class MyWorkspace(Workspace):

   def editables(self):
      result = {}
      for f in os.listdir(self.folder):
         if os.path.isdir(os.path.join(self.folder, f)):
            with open(os.path.join(self.folder, f, "name.txt")) as fname:
               name = fname.read().strip()
            with open(os.path.join(self.folder, f, "version.txt")) as fversion:
               version = fversion.read().strip()
            result[f"{name}/{version}"] = {"path": f}
      return result

It is also possible to re-use the conanfile.py logic in set_name() and set_version() methods, using the Workspace.load_conanfile() helper:

conanws.py¶

import os
from conan import Workspace

class MyWorkspace(Workspace):
   def editables(self):
      result = {}
      for f in os.listdir(self.folder):
         if os.path.isdir(os.path.join(self.folder, f)):
            conanfile = self.load_conanfile(f)
            result[f"{conanfile.name}/{conanfile.version}"] = {"path": f}
      return result

Workspace commands¶

conan workspace add/remove¶

Use these commands to add or remove editable packages to the current workspace. The conan workspace add <path> folder must contain a conanfile.py.

The conanws.py has a default implementation, but it is possible to override the default behavior:

conanws.py¶

import os
from conan import Workspace

class MyWorkspace(Workspace):
   def name(self):
      return "myws"

   def add(self, ref, path, *args, **kwargs):
      self.output.info(f"Adding {ref} at {path}")
      super().add(ref, path, *args, **kwargs)

   def remove(self, path, *args, **kwargs):
      self.output.info(f"Removing {path}")
      return super().remove(path, *args, **kwargs)

conan workspace info¶

Use this command to show information about the current workspace

$ cd myfolder
$ conan new workspace
$ conan workspace info
WARN: Workspace found
WARN: Workspace is a dev-only feature, exclusively for testing
name: myfolder
folder: /path/to/myfolder
products
   app1
editables
   liba/0.1
      path: liba
   libb/0.1
      path: libb
   app1/0.1
      path: app1

conan workspace open¶

The new conan workspace open command implements a new concept. Those packages containing an scm information in the conandata.yml (with git.coordinates_to_conandata()) can be automatically cloned and checkout inside the current workspace from their Conan recipe reference (including recipe revision).

conan new workspace¶

The command conan new has learned a new built-in (experimental) template workspace that creates a local project with some editable packages and a conanws.yml that represents it. It is useful for quick demos, proofs of concepts and experimentation.

conan workspace build¶

The command conan workspace build does the equivalent of conan build <product-path> --build=editable, for every product defined in the workspace.

Products are the “downstream” consumers, the “root” and starting node of dependency graphs. They can be defined with the conan workspace add <folder> --product new --product argument.

The conan workspace build command just iterates all products, so it might repeat the build of editables dependencies of the products. In most cases, it will be a no-op as the projects would be already built, but might still take some time. This is pending for optimization, but that will be done later, the important thing now is to focus on tools, UX, flows, and definitions (of things like the products).

conan workspace install¶

The command conan workspace install is useful to install and build the current workspace as a monolithic super-project of the editables. See next section.

Workspace monolithic builds¶

Conan workspaces can be built as a single monolithic project (sometimes called super-project), which can be very convenient. Let’s see it with an example:

$ conan new workspace
$ conan workspace install
$ cmake --preset conan-release # use conan-default in Win
$ cmake --build --preset conan-release

Let’s explain a bit what happened. First the conan new workspace created a template project with some relevant files:

The CMakeLists.txt defines the super-project with:

CMakeLists.txt¶

cmake_minimum_required(VERSION 3.25)
project(monorepo CXX)

include(FetchContent)

function(add_project SUBFOLDER)
   FetchContent_Declare(
      ${SUBFOLDER}
      SOURCE_DIR ${CMAKE_CURRENT_LIST_DIR}/${SUBFOLDER}
      SYSTEM
      OVERRIDE_FIND_PACKAGE
   )
   FetchContent_MakeAvailable(${SUBFOLDER})
endfunction()

add_project(liba)
# They should be defined in the liba/CMakeLists.txt, but we can fix it here
add_library(liba::liba ALIAS liba)
add_project(libb)
add_library(libb::libb ALIAS libb)
add_project(app1)

So basically, the super-project uses FetchContent to add the subfolders sub-projects. For this to work correctly, the subprojects must be CMake based sub projects with CMakeLists.txt. Also, the subprojects must define the correct targets as would be defined by the find_package() scripts, like liba::liba. If this is not the case, it is always possible to define some local ALIAS targets.

The other important part is the conanws.py file:

conanws.py¶

from conan import Workspace
from conan import ConanFile
from conan.tools.cmake import CMakeDeps, CMakeToolchain, cmake_layout

class MyWs(ConanFile):
   """ This is a special conanfile, used only for workspace definition of layout
   and generators. It shouldn't have requirements, tool_requirements. It shouldn't have
   build() or package() methods
   """
   settings = "os", "compiler", "build_type", "arch"

   def generate(self):
      deps = CMakeDeps(self)
      deps.generate()
      tc = CMakeToolchain(self)
      tc.generate()

   def layout(self):
      cmake_layout(self)

class Ws(Workspace):
   def root_conanfile(self):
      return MyWs  # Note this is the class name

The role of the class MyWs(ConanFile) embedded conanfile is important, it defines the super-project necessary generators and layout.

The conan workspace install does not install the different editables separately, for this command, the editables do not exist, they are just treated as a single “node” in the dependency graph, as they will be part of the super-project build. So there is only a single generated conan_toolchain.cmake and a single common set of dependencies xxx-config.cmake files for all super-project external dependencies.

The template above worked without external dependencies, but everything would work the same when there are external dependencies. This can be tested with:

$ conan new cmake_lib -d name=mymath
$ conan create .
$ conan new workspace -d requires=mymath/0.1
$ conan workspace install
$ cmake ...

Note

The current conan new workspace generates a CMake based super project. But it is possible to define a super-project using other build systems, like a MSBuild solution file that adds the different .vcxproj subprojects. As long as the super-project knows how to aggregate and manage the sub-projects, this is possible.

It might also be possible for the add() method in the conanws.py to manage the addition of the subprojects to the super-project, if there is some structure.

For any feedback, please open new tickets in https://github.com/conan-io/conan/issues.