Version: 1.21.0

Run detekt using a Git pre-commit hook

Detekt can be integrated into your development workflow by using a Git pre-commit hook. For that reason Git supports to run custom scripts automatically, when a specific action occurs. The mentioned pre-commit hook can be setup locally on your dev-machine. The following client-side detekt hook is triggered by a commit operation, and checks all files via the gradle task.

#!/usr/bin/env bash
echo "Running detekt check..."
OUTPUT="/tmp/detekt-$(date +%s)"
./gradlew detekt > $OUTPUT
EXIT_CODE=$?
if [ $EXIT_CODE -ne 0 ]; then
  cat $OUTPUT
  rm $OUTPUT
  echo "***********************************************"
  echo "                 Detekt failed                 "
  echo " Please fix the above issues before committing "
  echo "***********************************************"
  exit $EXIT_CODE
fi
rm $OUTPUT

The shell script can be installed by copying the content over to <<your-repo>>/.git/hooks/pre-commit. This pre-commit hook needs to be executable, so you may need to change the permission (chmod +x pre-commit). More information about Git hooks and how to install them can be found in Atlassian's tutorial.

A special thanks goes to Mohit Sarveiya for providing this shell script. You can watch his excellent talk about Static Code Analysis For Kotlin on YouTube.

Only run on staged files

It is also possible to use the CLI to create a hook that only runs on staged files. This has the advantage of speedier execution, by running on fewer files and avoiding the warm-up time of the gradle daemon.

Please note, however, that a handful of checks requiring type resolution will not work correctly with this approach. If you do adopt a partial hook, it is recommended that you still implement a full detekt check as part of your CI pipeline.

This example has been put together using pre-commit, but the same principle can be applied to any kind of hook.

Hook definition in pre-commit:

- id: detekt
  name: detekt check
  description: Runs `detekt` on modified .kt files.
  language: script
  entry: detekt.sh
  files: \.kt

Script detekt.sh:

#!/bin/bash

echo "Running detekt check..."
fileArray=($@)
detektInput=$(IFS=,;printf  "%s" "${fileArray[*]}")
echo "Input files: $detektInput"

OUTPUT=$(detekt --input "$detektInput" 2>&1)
EXIT_CODE=$?
if [ $EXIT_CODE -ne 0 ]; then
  echo $OUTPUT
  echo "***********************************************"
  echo "                 Detekt failed                 "
  echo " Please fix the above issues before committing "
  echo "***********************************************"
  exit $EXIT_CODE
fi

Only run on staged files​

Only run on staged files