colcon-pkg-config

0.1.0 · active · verified Fri Apr 17

colcon-pkg-config is a colcon extension that provides an environment hook to correctly set the `PKG_CONFIG_PATH` during `colcon build` operations. It ensures that `share/pkgconfig` directories of previously installed packages within the workspace are added to `PKG_CONFIG_PATH`, making `pkg-config` files discoverable for subsequent builds. The current version is 0.1.0, and its release cadence is infrequent, typically aligning with colcon core developments or specific ROS releases.

Common errors

```
Package 'my_lib' not found
```
cause During a `colcon build`, `pkg-config` failed to locate the `.pc` file for 'my_lib'. This often means the package providing 'my_lib' was not built/installed yet, `colcon-pkg-config` is not active, or `pkg-config` cannot find the `install/share/pkgconfig` directory.

fix Verify that the package providing 'my_lib' has been successfully built and installed (or symlinked) *before* the package attempting to use it. Confirm `colcon-pkg-config` is installed correctly in the same environment as `colcon`. Ensure `pkg-config` itself is installed on your system.
```
CMake Error at /usr/share/cmake-X.Y/Modules/FindPkgConfig.cmake:NNN (message): A required package was not found.
```
cause This is a common CMake error indicating that `pkg-config` (which CMake uses via `FindPkgConfig`) failed to find a required dependency's `.pc` file. This is the underlying CMake manifestation of the 'Package not found' issue.

fix As above, check the build order of your packages, ensure `colcon-pkg-config` is properly installed, and confirm `pkg-config` is available on your system. Sometimes cleaning and rebuilding the workspace (`colcon build --merge-install --cmake-args -DCMAKE_BUILD_TYPE=Release`) can resolve transient issues.

Warnings

gotcha colcon-pkg-config must be installed in the same Python environment (e.g., virtual environment or system Python) as your colcon-core installation for it to be discovered and activated. If they are in separate environments, the extension will not function.
Fix: Ensure `pip install colcon-pkg-config` is executed in the exact same Python environment where `colcon` is installed and active.
gotcha This extension only augments the `PKG_CONFIG_PATH` environment variable during the `colcon build` and `colcon install` steps. It does not ensure `pkg-config` itself is installed or in your system's PATH. If `pkg-config` is missing, you will still encounter errors.
Fix: Install the `pkg-config` utility via your system's package manager (e.g., `sudo apt install pkg-config` on Ubuntu/Debian, `brew install pkg-config` on macOS, `dnf install pkg-config` on Fedora).
gotcha When manually setting `PKG_CONFIG_PATH` in your shell, be aware that colcon-pkg-config will prepend workspace-specific paths. Depending on the order of precedence and how `pkg-config` resolves paths, your manual settings might be ignored or interfere with the automated ones. It's generally best to let colcon manage this path for workspace-internal dependencies.
Fix: For packages within a colcon workspace, rely on `colcon-pkg-config`. If external `pkg-config` paths are needed, consider managing them through a colcon `environment` hook or by sourcing environment setup files *before* your workspace's `setup.bash`.

Install

pip install colcon-pkg-config Install stable version

Quickstart

colcon-pkg-config is a plugin, not a library with direct user-facing Python imports or functions. Its quickstart involves installation and then simply running `colcon build` within a workspace, where it automatically enhances the build environment. The example above illustrates the conceptual steps, as `colcon build` is a shell command.

# colcon-pkg-config is a colcon extension and does not provide direct Python APIs for userland code.
# Its functionality is automatically integrated into the 'colcon build' process once installed.

# To use:
# 1. Install colcon-pkg-config in the same Python environment as colcon-core:
#    pip install colcon-pkg-config

# 2. Set up a colcon workspace with packages that produce and consume .pc files.
#    For example, 'pkg_a' installs 'libpkg_a.pc' and 'pkg_b' uses 'pkg-config --cflags --libs libpkg_a'.
#    mkdir -p my_colcon_ws/src/pkg_a
#    mkdir -p my_colcon_ws/src/pkg_b
#    # (populate pkg_a's CMakeLists.txt to install a .pc file to share/pkgconfig)
#    # (populate pkg_b's CMakeLists.txt to use find_package(PkgConfig) and pkg_check_modules(libpkg_a ...))

# 3. Build your colcon workspace from the root of 'my_colcon_ws':
#    import os
#    if os.path.exists('src'): # Simulate running in a colcon workspace
#        print('Building colcon workspace. colcon-pkg-config will automatically augment PKG_CONFIG_PATH.')
#        # This conceptual command would be run in a shell:
#        # os.system('colcon build --symlink-install')
#    else:
#        print('Please run this conceptual quickstart within a colcon workspace root.')

# The extension ensures that pkg_b correctly finds pkg_a's .pc file without manual PKG_CONFIG_PATH setup.

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