Development Tools

In the following, some tools that come in handy for the development of satellites for Constellation of the framework itself are described. These tools are pre-configured in the satellite project templates, and are also used in the same or a very similar configuration in the main Constellation repository.

Their goal is to ensure a coherent code base in terms of style, naming conventions and best practices. A detailed description of the formatting and naming conventions chosen for the main Constellation repository can be found in the Framework Development Guide.

Formatting & Linting for C++

The clang-format tool is used to apply the project’s coding style convention to all C++ files of the code base. The format is defined in the .clang-format file in the root directory of the satellite project template as well as the main repository and mostly follows the suggestions defined by the standard LLVM style with minor modifications. Most notably are the consistent usage of four white space characters as indentation and the column limit of 125 characters.

The clang-tidy tool provides linting of the source code. The tool tries to detect possible errors (and thus potential bugs), dangerous constructs (such as uninitialized variables) as well as stylistic errors. In addition, it ensures proper usage of modern C++ standards. The configuration used for the clang-tidy command can be found in the .clang-tidy file in the root directory of the satellite project template as well as the main repository.

These rules are applied automatically when committing code to the repository via the pre-commit hooks. Alternatively, the tools can also be manually executed after configuring the build with either meson or CMake using the following commands:

ninja -C builddir/ clang-format
ninja -C builddir/ clang-tidy

Using pre-commit

The Constellation repository uses pre-commit hooks to enforce common formatting and naming conventions. pre-commit is a package manager for hooks to be run before committing code changes to the repository.

It needs to be activated once for the cloned repository by running:

pre-commit install

Now, pre-commit will run the configured checks every time a new commit is created and an output similar to the following is produced:

$ git commit

check for merge conflicts................................................Passed
check that scripts with shebangs are executable..........................Passed
fix end of files.........................................................Passed
fix utf-8 byte order marker..............................................Passed
mixed line ending........................................................Passed
don`t commit to branch...................................................Failed
- hook id: no-commit-to-branch
- exit code: 1
trim trailing whitespace.................................................Passed
codespell................................................................Passed
markdownlint.............................................................Passed
reuse lint-file..........................................................Passed

Here, the creation of the commit has been prevented because one of the checks has failed - in this case the check to not commit to the main branch. New changes resolving the reported issues have to be added to the commit diff before attempting to commit anew.

Sometimes it is necessary to temporarily skip these checks for a specific commit. This can be achieved by using:

git commit --no-verify

By default, pre-commit will run its checks only on files that have been modified in a commit. In order to run pre-commit on all files of the repository instead, this command can be used:

pre-commit run --all-files

Software BOM with reuse

Constellation follows the REUSE recommendations for accessible software licensing. Every file of the repository clearly states its license along with the copyright statement in a machine-readable format, e.g. for a C++ source file

/**
 * @file
 * @brief Description of the file content
 *
 * @copyright Copyright (c) 2025 DESY and the Constellation authors.
 * This software is distributed under the terms of the EUPL-1.2 License, copied verbatim in the file "LICENSE.md".
 * SPDX-License-Identifier: EUPL-1.2
 */

and the Python equivalent

"""
SPDX-FileCopyrightText: 2024 DESY and the Constellation authors
SPDX-License-Identifier: EUPL-1.2
"""

The reuse tool can be used to check compliance with the REUSE recommendations with the command

reuse lint

This command is part of the pre-commit hooks. A software bill of material (BOM) on the SPDX format can be generated using

reuse spdx