Thank you for your interest in this project! Please refer to the following sections on how to contribute code and bug reports. ### Reporting bugs Before submitting a question or bug report, please take a moment of your time and ensure that your issue isn't already discussed in the project documentation provided at [pybind11.readthedocs.org][] or in the [issue tracker][]. You can also check [gitter][] to see if it came up before. Assuming that you have identified a previously unknown problem or an important question, it's essential that you submit a self-contained and minimal piece of code that reproduces the problem. In other words: no external dependencies, isolate the function(s) that cause breakage, submit matched and complete C++ and Python snippets that can be easily compiled and run in isolation; or ideally make a small PR with a failing test case that can be used as a starting point. ## Pull requests Contributions are submitted, reviewed, and accepted using GitHub pull requests. Please refer to [this article][using pull requests] for details and adhere to the following rules to make the process as smooth as possible: * Make a new branch for every feature you're working on. * Make small and clean pull requests that are easy to review but make sure they do add value by themselves. * Add tests for any new functionality and run the test suite (`cmake --build build --target pytest`) to ensure that no existing features break. * Please run [`pre-commit`][pre-commit] to check your code matches the project style. (Note that `gawk` is required.) Use `pre-commit run --all-files` before committing (or use installed-mode, check pre-commit docs) to verify your code passes before pushing to save time. * This project has a strong focus on providing general solutions using a minimal amount of code, thus small pull requests are greatly preferred. ### Licensing of contributions pybind11 is provided under a BSD-style license that can be found in the ``LICENSE`` file. By using, distributing, or contributing to this project, you agree to the terms and conditions of this license. You are under no obligation whatsoever to provide any bug fixes, patches, or upgrades to the features, functionality or performance of the source code ("Enhancements") to anyone; however, if you choose to make your Enhancements available either publicly, or directly to the author of this software, without imposing a separate written license agreement for such Enhancements, then you hereby grant the following license: a non-exclusive, royalty-free perpetual license to install, use, modify, prepare derivative works, incorporate into other computer software, distribute, and sublicense such enhancements or derivative works thereof, in binary and source code form. ## Development of pybind11 To setup an ideal development environment, run the following commands on a system with CMake 3.14+: ```bash python3 -m venv venv source venv/bin/activate pip install -r tests/requirements.txt cmake -S . -B build -DDOWNLOAD_CATCH=ON -DDOWNLOAD_EIGEN=ON cmake --build build -j4 ``` Tips: * You can use `virtualenv` (from PyPI) instead of `venv` (which is Python 3 only). * You can select any name for your environment folder; if it contains "env" it will be ignored by git. * If you don’t have CMake 3.14+, just add “cmake” to the pip install command. * You can use `-DPYBIND11_FINDPYTHON=ON` to use FindPython on CMake 3.12+ * In classic mode, you may need to set `-DPYTHON_EXECUTABLE=/path/to/python`. FindPython uses `-DPython_ROOT_DIR=/path/to` or `-DPython_EXECUTABLE=/path/to/python`. ### Configuration options In CMake, configuration options are given with “-D”. Options are stored in the build directory, in the `CMakeCache.txt` file, so they are remembered for each build directory. Two selections are special - the generator, given with `-G`, and the compiler, which is selected based on environment variables `CXX` and similar, or `-DCMAKE_CXX_COMPILER=`. Unlike the others, these cannot be changed after the initial run. The valid options are: * `-DCMAKE_BUILD_TYPE`: Release, Debug, MinSizeRel, RelWithDebInfo * `-DPYBIND11_FINDPYTHON=ON`: Use CMake 3.12+’s FindPython instead of the classic, deprecated, custom FindPythonLibs * `-DPYBIND11_NOPYTHON=ON`: Disable all Python searching (disables tests) * `-DBUILD_TESTING=ON`: Enable the tests * `-DDOWNLOAD_CATCH=ON`: Download catch to build the C++ tests * `-DOWNLOAD_EIGEN=ON`: Download Eigen for the NumPy tests * `-DPYBIND11_INSTALL=ON/OFF`: Enable the install target (on by default for the master project) * `-DUSE_PYTHON_INSTALL_DIR=ON`: Try to install into the python dir
A few standard CMake tricks: (click to expand)

* Use `cmake --build build -v` to see the commands used to build the files. * Use `cmake build -LH` to list the CMake options with help. * Use `ccmake` if available to see a curses (terminal) gui, or `cmake-gui` for a completely graphical interface (not present in the PyPI package). * Use `cmake --build build -j12` to build with 12 cores (for example). * Use `-G` and the name of a generator to use something different. `cmake --help` lists the generators available. - On Unix, setting `CMAKE_GENERATER=Ninja` in your environment will give you automatic mulithreading on all your CMake projects! * Open the `CMakeLists.txt` with QtCreator to generate for that IDE. * You can use `-DCMAKE_EXPORT_COMPILE_COMMANDS=ON` to generate the `.json` file that some tools expect.

To run the tests, you can "build" the check target: ```bash cmake --build build --target check ``` `--target` can be spelled `-t` in CMake 3.15+. You can also run individual tests with these targets: * `pytest`: Python tests only * `cpptest`: C++ tests only * `test_cmake_build`: Install / subdirectory tests If you want to build just a subset of tests, use `-DPYBIND11_TEST_OVERRIDE="test_callbacks.cpp;test_pickling.cpp"`. If this is empty, all tests will be built. ### Formatting All formatting is handled by pre-commit. Install with brew (macOS) or pip (any OS): ```bash # Any OS python3 -m pip install pre-commit # OR macOS with homebrew: brew install pre-commit ``` Then, you can run it on the items you've added to your staging area, or all files: ```bash pre-commit run # OR pre-commit run --all-files ``` And, if you want to always use it, you can install it as a git hook (hence the name, pre-commit): ```bash pre-commit install ``` [pre-commit]: https://pre-commit.com [pybind11.readthedocs.org]: http://pybind11.readthedocs.org/en/latest [issue tracker]: https://github.com/pybind/pybind11/issues [gitter]: https://gitter.im/pybind/Lobby [using pull requests]: https://help.github.com/articles/using-pull-requests