Disable eslint (or rather, lower the level of violation to a warning) for existing errors given a JSON output of an eslint run

command.sh

# Command to generate the ignorables
npx eslint --quiet -o ignorable-lint.json --format json --ext '.js' app/

insert-eslint-disables.js

const fs = require('fs');
const { uniq } = require('lodash');

function prependToFile(filePath, insert) {
    const data = fs.readFileSync(filePath)
    const fd = fs.openSync(filePath, 'w+')
    fs.writeSync(fd, insert, 0, insert.length, 0)
    fs.writeSync(fd, data, 0, data.length, insert.length)
    fs.close(fd, (err) => {
        if (err) throw err;
    });
}

function insertIgnoresOnViolations(violations) {
    violations.forEach(({ filePath, messages }) => {
        const ruleIds = uniq(messages.map(({ ruleId }) => ruleId));
        const disableStatement = `/* eslint ${ruleIds.map(ruleId => `${ruleId}: "warn"`).join(', ')} */\n\n`;
        const insert = new Buffer(disableStatement);
        prependToFile(filePath, insert);
    })
}

let input = '';

process.stdin.resume();
process.stdin.setEncoding('utf8');

process.stdin.on('data', function (chunk) {
    input += chunk;
});

process.stdin.on('end', function () {
    var parsedData = JSON.parse(input);
    insertIgnoresOnViolations(parsedData);
});