Introduction

Cardboardlint is a cheap lint solution for pull requests.

It is a non-hosted and customizable tool similar to commercial services like:

• Hound CI: https://houndci.com/
• Stickler CI: https://stickler-ci.com/
• landscape.io: https://landscape.io/
• ...

For more advanced analysis, one could use Coverty Scan. (https://scan.coverity.com/)

Cardboardlint wraps a collection of linters, intended to be used on a project in a Git repository. Cardboardlint is able to report just those messages related to lines that have changed in your development branch, compared to another commit, e.g. the HEAD of the master branch. This is intended to make life easier for contributors to a project: in their pull requests, they will only see linting issues related to the code they have touched. For some linters, cardboardlint also supports automatic fixes of linting issues, optionally restricted to code that has changed in your development branch.

Some example projects that use Cardboardlint:

• Cardboardlint, obviously
• Roberto: https://github.com/theochem/roberto (Cardboardlint also uses Roberto.)
• IOData: https://github.com/theochem/iodata
• CellCutoff: https://github.com/theochem/cellcutoff
• CGrid: https://github.com/theochem/cgrid

Usage

• Install cardboardlint, which requires python 3.6 or 3.7 and PyYaml. You must have Python 3 installed, PyYaml will be installed automatically for you with the instructions below.

  # Install cardboardlint with pip. Any of the following that works for you
  # is fine:
  pip install cardboardlint
  pip install cardboardlint --user
  python3 -m pip install cardboardlint
  python3 -m pip install cardboardlint --user
  # Or install cardboardlint with conda:
  conda install theochem::cardboardlint

• Add a .cardboardlint.yml to the root of your source tree. It should at least contain a linters section with a list of linters, e.g.

  linters:
  - pylint:
      pylintrc: tools/your_custom_pylintrc
  - cppcheck:
  - import:
  ...

  A list of supported linters is easily deduced from the source code. Just look into the cardboardlint/linter_*.py files. Each of these files has a module docstring with some explanations and a DEFAULT_CONFIG dictionary with the available configuration vars.

  You can repeat any linter multiple times with different configuration settings. This can be useful, e.g. when unit tests must be linted differently than the rest of the source code. This is a simple example where unit tests have a different pylint config:

  pre_filefilter: ['+ tools/demo/*.py', '- tools/*', '+ *']
  
  linters:
  - pylint:
      pylintrc: tools/pylintrc
      filefilter: ['- test_*.py', '+ *.py']
      exclude:
  - pylint:
      pylintrc: tools/pylintrc_tests
      filefilter: ['+ test_*.py']
  - import:
  ...

  When cardboardlint starts, it makes a list of files not ignored by git in the current repository. These filenames are first filtered by a so-called pre_filefilter. Files that pass the pre_filefilter are then tested with linter-specific filefilters to end up with a list of files to be checked by a given linter.

  A pre_filefilter or filefilter consists of a list of rules to test if a file should be considered for linting or not. Each rule starts with a possible outcome, + (include) or a - (exclude), followed by a glob pattern. At the moment, the pattern ignores the presence of directory separators and treats the complete path as a single string on which the pattern is tested, using Pythons fnmatch builtin module. The rules are tested in order and when a pattern matches, the corresponding decision is made (include and exclude), without considering subsequent rules. When no patterns give a match, the file is excluded.

  The following tricks might be useful:

  • If you would like to include files that did not match any pattern, add '+ *' as last pattern, which is often useful for the pre_filefilter.
  • If you would like to include all python files, in all directories, use '+ *.py'. The wildcard will also match directories containing the Python file. For example it would match a/b in the path a/b.py.

• Install the linters you intend to run (either locally or in your CI environment). These dependencies are not installed automatically because you may not want to use all of them.

  Conda packages for all supported linters can be found in the main conda channels an in conda-forge (https://anaconda.org/conda-forge). We have added packages to conda-forge for cppcheck and cpplint. All other linters were already available. To install all of them, we can recommend the following commands:

  # Add conda-forga channel with lower priority as the default channels. This
  # prevents your conda env from being flooded by conda-forga packages.
  conda config --append channels conda-forge
  # Install all linters for which cardboardlint has wrappers:
  conda install pycodestyle pydocstyle cppcheck cpplint yamllint flake8 \
                doxygen pylint autopep8, yapf, black

• Run the cardboardlinter, which can be done in several ways:

  # runs all linters and use multiple cpus
  cardboardlinter -n auto
  # runs all linters and only shows messages for changes relative to master
  cardboardlinter -r master
  # run only static linters
  cardboardlinter -f static
  # run only dynamic linters, which require in-place build
  cardboardlinter -f dynamic
  
  # run fixers, which automaticaly solve trivial problems
  cardboardlinter -F
  # run fixers, which automaticaly solve trivial problems, only on those
  # lines that have changed w.r.t. the master branch.
  cardboardlinter -F -r master

• Usage in CI:

  • Travis-CI (in .travis.yml). This will only report messages for lines that have changed in the PR.

    install:
    # Install the latest cardboardlinter
    - if [ "$TRAVIS_PULL_REQUEST" != "false" ]; then
        pip install --upgrade cardboardlint
      fi
    
    script:
    # Run the cardboardlinter, in case of pull requests
    - if [ "$TRAVIS_PULL_REQUEST" != "false" ]; then
        cardboardlinter --refspec $TRAVIS_BRANCH -n auto;
      fi

  • One can also use Roberto to drive the entire build+test+package workflow, which includes linting with Cardboardlint. See https://theochem.github.io/roberto/

Change log

• Version 1.3.1 August 26, 2020

  • Improve interaction with Roberto.
  • Hide duplicate messages.

• Version 1.3.0 April 14, 2019

  • More verbose output. List of selected files for linting is always shown.
  • Fix default location for Python command-line scripts is ./bin, not ./scripts.
  • Wall time of linters is printed.
  • Few cleanups.

• Version 1.2.0 April 12, 2019

  • Added support for fixers. The following liners can also fix problems: header, whitespace, autopep8, yapf, black. The latter three are new.
  • Removed some Python-2 compatibility code.
  • Replace nosetests by pytest.
  • Add more context to README.
  • Add RST linter.

• Version 1.1.0 April 3, 2019

  • Add option for number of processors to use.

• Version 1.0.1 March 30, 2019

  • Add missing config options for cpplint.

• Version 1.0.0 March 27, 2019

  First release, mainly in anticipation of API-breaking changes, which will result in a major version increase. By making a release, we can handle this change in API gracefully. Notable features include:

  • Support for the following linters: cppcheck, ccplint, doxygen, flake8, header (internal), import (internal), namespace (internal), pycodestyle, pydocstyle, pylint, whitespace (internal), yamllint
  • For all supported linters, the output can be restricted to files and (lines in those files) that have changed between two git commits. In pull requests, this will then only show errors that are relevant for the code touched in the PR. This is intended for making life easy for contributors, i.e. to not bother them with linting issues in code they have not touched.
  • Flexible file filtering, essentially a simplified version of rsync's file filtering rules.
  • Consistent and colored output for all linters, making it easy to process linting issues.