PreCommit Hook - Convert Tab to Spaces for Golang Files

pre-commit

#!/bin/bash

# Print an introduction line in cyan
printf "\033[0;36mPre-commit hook - For Checking Tabs in Golang Files...\033[0m \n"

# Grab feed of staged files 
files=$(git diff --name-only --cached  -- "*.go")
numfiles=$( printf '%s' "$files" | grep -c '^' )

if [ $numfiles -eq 0 ]
then
  printf "\033[0;35mNo Golang files staged. This precommit hook need not run.\033[0m\n"
  exit 0
fi

# Default to zero which means the changes are good and the commit can go ahead
exitstatus=0

numnonpassingfiles=0

# Iterate over the filenames to discover the longest 
longest=0
for i in $files
do
  if [ ${#i} -gt $longest ]
  then
    longest=${#i}
  fi
done

# Iterate over the staged filenames
for i in $files
do
  # Print file name eg: "Checking: text.txt"
  printf "\033[0;35mChecking:\033[0m %s " "$i" 

  # Print some padding spaces so the failed/success statuses line up
  padding=$(expr $longest - ${#i})
  for ((n=0;n<$padding;n++))
  do
    printf " " 
  done

  # Count number of lines with the plus symbol and tab characters at the start (eg. New lines, indented wrongly)
  tabbedlines=$( git diff --cached -U0 -- $i | egrep "^\+	" )
  tabbedlinecount=$( printf "%s" "$tabbedlines" | grep -c '^' )

  # Print the coloured [failed] or [success] report 
  if [ $tabbedlinecount -gt 0 ]
  then
    printf "\033[0;31m[failed]\n"
    ((numnonpassingfiles++))
    exitstatus=1
  else
    printf "\033[0;32m[passed]\n"
  fi

  # Print report line about tab character being used
  if [ $tabbedlinecount -gt 0 ]
  then
    printf "%s lines indented with a tab character: \033[0;32m \n" "$tabbedlinecount"
    while read -r line;
    do
      printf "%s\n" "$line"
    done <<< "$tabbedlines"
    printf "\n"
    printf "Converting Tabs to Spaces.. you'll need to add the file again\n"
    expand -t4 `echo $i` | sponge `echo $i`
  fi

  # Reset print color back to default for the next iteration
  printf "\033[0m"

done

# Print a summary of lint
if [ $exitstatus -eq 0 ]
then
  printf "\033[0;32m%s %s file" "--" "$numfiles"
  if [ $numfiles -gt 1 ]
  then
    printf "s"
  fi
  printf " passed. Continuing with commit... \033[0m\n"
else
  printf "%s Sorry, %s of %s staged files contain lines that do not pass.\n" "--" "$numnonpassingfiles" "$numfiles"
fi

exit $exitstatus

precommit-hook.md

PreCommit Hook

A pre-commit hook is added locally to the .git/hooks folder and is executed before you can add a commit message.

Pre-Requisite

In this script we use expand and sponge commands, so you need to have the relevant libraries installed.

To install for Ubuntu,

apt get -y moreutils

Adding the Script

Inside .git/hooks directory, create a file pre-commit and add the lines in the pre-commit file below.

How To?

• Add the files via VSCode, or git add -A
• After you type your commit message, the pre-commit script will be executed. It'll change the file and you need to add it back again.

References

Completely built out of - this script