pylint-exit

Utility to handle pylint exit codes on Linux in a scripting-friendly way.

Pylint uses bit-encoded exit codes to convey the results of the pylint review, which means it will return with a non-zero return code even when the pylint scoring was successful.

This can make it difficult to script the execution of pylint while at the same time detecting genuine errors.

pylint-exit is a small command-line utility that can be used to re-process the pylint return code and translate it into a scripting-friendly return code.

pylint-exit will decode the bit-encoded return code, identify whether there were any fatal messages issued (which might constitute a failure in the execution of pylint), or a usage error, and return a 0 or 1 return code that is more easily used in shell scripts.

Installation

The simplest way to install is via pip.

pip install pylint-exit

This will install the package, and will provide the pylint-exit command line utility.

You can also manually install by downloading pylint_exit.py, and make it executable.

curl -o pylint-exit https://raw.githubusercontent.com/jongracecox/pylint-exit/master/pylint_exit.py && chmod +x pylint_exit.py

You should also consider creating a symbolic link so that the calls in the remainder of this README work as described. Update <path-to> with where you downloaded the script.

ln -s <path-to>/pylint_exit.py /usr/local/bin/pylint-exit

Note: If you perform a --user install with pip then you will need to ensure ~/.local/bin appears in your PATH environment variable, otherwise the command line pylint-exit will not work.

Usage

Add || pylint-exit $? to the end of your existing Pylint command. You can then use the updated $? return code in your shell script.

pylint mymodule.py || pylint-exit $?
if [ $? -ne 0 ]; then
  echo "An error occurred while running pylint." >&2
  exit 1
fi

Note: Many CI tools will check the return code of each command, so it may be enough to simply add || pylint-exit $?, and leave the return code check to the CI executor.

You can also use the python code directly if needed:

pylint mymodule.py || python pylint_exit.py $?

Return codes

Pylint can return combinations of the following codes. pylint-exit will identify each issued message, and return the maximum final return code.

Pylint code	Message	Final return code
1	Fatal message issued	1
2	Error message issued	0
4	Warning message issued	0
8	Refactor message issued	0
16	Convention message issued	0
32	Usage error	1

This list is stored in exit_codes_list, which can be customised if needed.

You can control what is considered a failure using the following command line arguments. By default these types of messages don't cause a non-zero return code. Adding any of these arguments will trigger a non-zero return code when those types of message are raised.

Name	Meaning
-efail, --error-fail	Fail on issued error messages.
-wfail, --warn-fail	Fail on issued warning messages.
-rfail, --refactor-fail	Fail on issued refactor messages.
-cfail, --convention-fail	Fail on issued convension messages.

Examples

Exiting gracefully on non-severe messages

In this example pylint issues refactor and convention messages, and exits with a return code of 24. pylint-exit decodes this, displays the messages, and exits with a return code of 0.

> pylint --rcfile=.pylintrc --output-format=text mymodule.py || pylint-exit $?
The following messages were raised:

  - refactor message issued
  - convention message issued
 
No fatal messages detected.  Exiting gracefully...
> echo $?
0

Exiting with an error on severe messages

In this example pylint returns with a usage error due to the bad output format, and exits with a return code of 32. pylint-exit detects this, displays the message, and returns with an exit code of 1.

> pylint --rcfile=.pylintrc --output-format=badformat mymodule.py || pylint-exit $?
The following messages were raised:

  - usage error

Fatal messages detected.  Failing...
> echo $?
1

Treating errors and warnings as severe

In this example we will use the --error-fail and --warn-fail command line arguments to cause pylint-exit to treat errors and warnings as serious enough to return a non-zero return code.

In the example scenario pylint issues error and warning messages, and exits with a return code of 6. pylint-exit decodes this, displays the messages, and exits with a return code of 1 because the error and warning messages are now considered as fatal.

> pylint --rcfile=.pylintrc --output-format=badformat mymodule.py || pylint-exit --error-fail --warn-fail $?
The following messages were raised:

  - error message issued
  - warning message issued

Fatal messages detected.  Failing...
> echo $?
1

Testing

You can test how pylint-exit will react to various return codes using the following command:

(exit 6) || pylint-exit $?

or if you are using the python code directly:

(exit 6) || python pylint_exit.py $?