Lint Staged Handle Partially Staged Files

lint-staged-precommit.sh

#!/bin/bash

NPM_COMMAND=$1
STAGED_FILE=$2
IS_PARTIALLY_STAGED=$(git diff --name-only "$STAGED_FILE")

if [[ "$IS_PARTIALLY_STAGED" != "" ]];
then
    # If the file is partially changed, we need get the hash so we can see if it changed later
    PRE_LINT_HASH=$(git hash-object "$STAGED_FILE")
fi

# Do the actual linting fixing
npm run "$NPM_COMMAND" "$STAGED_FILE"

if [[ "$?" != "0" ]];
then
    echo "Error occurred in npm run $NPM_COMMAND. Exitting..."
    exit 1
fi


if [[ "$IS_PARTIALLY_STAGED" != "" ]];
then
    # If it was partially staged, compare it to the file on disk before linting to see if it changed
    POST_LINT_HASH=$(git hash-object "$STAGED_FILE")

    if [[ "$POST_LINT_HASH" != "$PRE_LINT_HASH" ]];
    then
        echo "A partially staged file was fixed during linting precommit hook. $STAGED_FILE"
        echo "Please re-stage the file hunks and retry commit"
        exit 1
    fi
else
    # If the entire file was previously staged, we should simply re-add the linting changes to this commit
    git add "$STAGED_FILE"
fi

package.json

{
  // ...
  "scripts": {
    "lint:fix": " ... "
  },
  "lint-staged": {
    "src/**/*.js": [
      "./lint-staged-precommit.sh lint:fix"
    ]
  }
}

I use this to handle the case when partially staged files are modified during "lint-staged". This allows me to "re-think" my commit. If I take no action and simply run again, everything passes since my files were not modified again.