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Developing Recipes Locally

Before you can contribute any code changes, you'll need to make sure you are familiar with the Conan client and have an environment that is conducive to developing recipes.

This file is intended to provide all the commands you need to run in order to be an expert ConanCenter contributor.

Contents

Clone your fork

  1. Follow the GitHub UI to fork this repository
  2. Clone your fork

Setup your environment

  1. Install a C++ development toolchain - ConanCenter's build images are available
  2. Install the Conan client - make sure to keep it up to date!
  3. Install CMake - this is the only tool which is assumed to be present see FAQ for details.

Note: It's recommended to use a dedicated Python virtualenv when installing with pip.

Installing the ConanCenter Hooks

The system will use the conan-center hooks to perform some quality checks. You can install the hooks by running:

conan config install https://github.com/conan-io/hooks.git -sf hooks -tf hooks
conan config set hooks.conan-center

Note: Hooks are generally for package correctness and the pylinters are for the recipe syntax

The hooks will show error messages but the conan create won’t fail unless you export the environment variable CONAN_HOOK_ERROR_LEVEL=40. All hooks checks will print a similar message:

[HOOK - conan-center.py] post_source(): [LIBCXX MANAGEMENT (KB-H011)] OK
[HOOK - conan-center.py] post_package(): ERROR: [PACKAGE LICENSE] No package licenses found

Updating conan hooks on your machine

The hooks are updated from time to time, so it's worth keeping your own copy of the hooks updated regularly. To do this, simply run:

conan config install

Basic Commands

We recommend working from the recipes/project folder itself. You can learn about the recipe file structure to understand the folder and files located there.

Note: You can only change one recipe per pull request, and working from the recipe folder will help prevent making a few mistakes. The default for this folder is all, follow the link above to learn more.

The entire workflow of a recipe can be execute with the conan create. This should look like:

  • conan create all/conanfile.py 0.0.0@ -pr:b=default -pr:h=default

ConanCenter also has a few support settings and options which highly recommend to test. For example conan create all/conanfile.py 0.0.0@ -o project:shared=True -s build_type=Debug is a easy way to test more configurations ensuring the package is correct.

Try it yourself

For instance you can create packages for fmt in various supported configurations by running:

cd recipes/fmt
conan create all/conanfile.py fmt/9.0.0@ -pr:b=default -pr:h=default
conan create all/conanfile.py fmt/9.0.0@ -o fmt:header_only=True -pr:b=default -pr:h=default
conan create all/conanfile.py fmt/9.0.0@ -s build_type=Debug -o fmt:shared=True -pr:b=default -pr:h=default

Debugging Failed Builds

Some common errors related to Conan can be found on troubleshooting section. For ConanCenter Hook errors, go to the Error Knowledge Base page to know more about those.

To test with the same environment, the build images are available. Instructions for using these images can be found in Testing more environments section.

In ConanCenterIndex, the most common failure point is upstream build scripts tailored to their specific use cases. It's not uncommon to patch build scripts but make sure to read the patch policy. You are encouraged to submit pull requests upstream.

Running the Python Linters

Linters are always executed by GitHub Actions to validate parts of your recipe, for instance, if it uses migrated Conan tools imports.

It is possible to run the linter locally the same way it is being run using Github actions by:

  • (Recommended) Use a dedicated Python virtualenv.

  • Ensure you have required tools installed: conan and pylint (better to uses fixed versions)

    pip install conan~=1.0 pylint==2.14

  • Set environment variable PYTHONPATH to the root of the repository

    export PYTHONPATH=your/path/conan-center-index

  • Now you just need to execute the pylint commands:

    # Lint a recipe:
pylint --rcfile=linter/pylintrc_recipe recipes/fmt/all/conanfile.py

# Lint the test_package
pylint --rcfile=linter/pylintrc_testpackage recipes/fmt/all/test_package/conanfile.py

Running the YAML Linters

There's two levels of YAML validation, first is syntax and the second is schema. The style rules are located in linter/yamllint_rules.yml and are used to ensure consistence. The config.yml is required for the build infrastructure and the conandata.yml patch fields have required elements that are enforced with schema validation. There's are to encourage the best possible quality of recipes and make reviewing faster.

Yamllint

  • (Recommended) Use a dedicated Python virtualenv.

  • Ensure you have required tools installed: yamllint (better to uses fixed versions)

    pip install yamllint==1.28

  • Now you just need to execute the yamllint commands:

    # Lint a recipe:
yamllint --config-file linter/yamllint_rules.yml -f standard recipes/fmt/all/conanfile.py

# Lint the test_package (same command)
yamllint --config-file linter/yamllint_rules.yml -f standard recipes/fmt/all/test_package/conanfile.py

Yamlschema

  • (Recommended) Use a dedicated Python virtualenv.

  • Ensure you have required tools installed: strictyaml and argparse (better to uses fixed versions)

    pip install strictyaml==1.16 argparse==1.4

  • Now you just need to execute the validation scripts:

    # Lint a config.yml:
python3 linter/config_yaml_linter.py recipes/fmt/config.yml

# Lint a conandata.yml
python3 linter/conandata_yaml_linter.py recipes/fmt/all/conandata.yml

Testing the different test_*_package

This can be selected when calling conan create or separately with conan test

# By adding the `-tf` argument
conan create recipes/fmt/all/conanfile.py 9.0.0@ -tf test_v1_package/ -pr:b=default -pr:h=default
# Passing test package's conanfile directly (make sure to export first)
conan test recipes/fmt/all/test_v1_package/conanfile.py fmt/9.0.0@ -pr:h=default -pr:b=default

Testing more environments

This can be difficult for some platforms given virtualization support.

For Windows and MacOS users, you can test the Linux build environments with the Docker build images.

Assuming you've already tested it locally and it's been successfully exported to your cache, you can:

  1. Creating a new profile.
    • You can also download them from CCI build summary
  2. Build missing packages

Example.

docker run -v/Users/barbarian/.conan:/home/conan/.conan conanio/gcc8 bash -c "conan profile new --detect gcc8"
docker run -v/Users/barbarian/.conan:/home/conan/.conan conanio/gcc8 bash -c "conan install -pr gcc8 fmt/9.0.0@ --build missing"

Note: If you are running on Mac M1, the follow Docker argument is required: --platform=linux/amd64

If you are working with packages that have system dependencies that are managed by Conan

docker run -e CONAN_SYSREQUIRES_MODE=enabled conanio/gcc11-ubuntu16.04 conan install fmt/9.0.0@ -if build --build missing -c tools.system.package_manager:mode=install -c tools.system.package_manager:sudo=yes

Using Conan 2.0

Everything you need to know about the methods, commands line, outputs can be found in the Conan 2.0 Migrations docs.

This should be non-intrusive. Conan 2.0 by default has a different CONAN_USER_HOME location, which means that it has separate caches, profiles, and settings. This will leave your Conan 1.0 setup completely intact when using Conan 2.0.

Note: There are substantial changes to the CLI so very few of the commands will remain the same. The new Unified Command Pattern, as an example, changes how settings and options are passed.

Installing Conan 2.0 beta

Simply install Conan 2.0 with pip install conan --upgrade --pre.

You can confirm the installation with:

$ conan --version
Conan version 2.0.0-beta3
$ conan config home
Current Conan home: /Users/barbarian/.conan2

Note: You will most likely see

Initialized file: '/Users/barbarian/.conan2/settings.yml'
Initialized file: '/Users/barbarian/.conan2/extensions/plugins/compatibility/compatibility.py'
Initialized file: '/Users/barbarian/.conan2/extensions/plugins/compatibility/app_compat.py'
Initialized file: '/Users/barbarian/.conan2/extensions/plugins/compatibility/cppstd_compat.py'
Initialized file: '/Users/barbarian/.conan2/extensions/plugins/profile.py'

When running the client for the first time.

You will need to setup profiles. This is one of the changes in 2.0. The default profile is now opt-in and no longer generated automatically.

conan profile detect

Warning: This is a best guess, you need to make sure it's correct.

Trying it out

Try building an existing recipe. We'll repeat the 1.x example with fmt to build the same configurations:

cd recipes/fmt
conan create all/conanfile.py --version 9.0.0
conan create all/conanfile.py --version 9.0.0 -o fmt/9.0.0:header_only=True
conan create all/conanfile.py --version 9.0.0 -s build_type=Debug -o fmt/9.0.0:shared=True