Precommit script for bumping patch version

versionBump.js

/**
 * Precommit script:
 *
 * Script will bump the minor version in the package.json unless the version was
 * changed manually (in which case the version number is left unchanged)
 */

const fs = require("fs");
const path = require("path");
const { exec } = require("child_process");
const { promisify } = require("util");

const read = promisify(fs.readFile);
const view = promisify(exec);

const pathToPackage = path.resolve(__dirname, "./package.json");

const runAsync = async () => {
  const previousFile = await view("git show HEAD:package.json").then(val => {
    return val.stdout;
  });
  const currentFile = await read(pathToPackage).then(val => {
    return val.toString();
  });

  if (versionIsSame(previousFile, currentFile)) {
    const newVersion = incrementVersion(currentFile);
    fs.writeFile(pathToPackage, newVersion, err => {
      exec(`git add ${pathToPackage}`, () => {
        console.log("Patch version bumped by one...");
      });
    });
  }
};

runAsync();

/**
 * Take a string representing a package.json file
 * and increment the version value in it.
 */
const incrementVersion = inputPkgJson => {
  versionRE = /"(\d+)\.(\d+)\.(\d+)"/;
  const inputArray = inputPkgJson.split("\n");
  const versionLineIndex = inputArray.findIndex(e => {
    return e.toLowerCase().includes('"version"');
  });
  const oldVersion = inputArray[versionLineIndex];
  const minorValue = oldVersion.match(versionRE)[3];
  const incrementedValue = parseInt(minorValue, 10) + 1;
  const newVersionLine = oldVersion.replace(
    versionRE,
    `"$1.$2.${incrementedValue}"`
  );
  inputArray[versionLineIndex] = newVersionLine;

  return inputArray.join("\n");
};

/**
 * Predicate: returns true only if the version number is same for both contents
 */
const versionIsSame = (prev, curr) => {
  const previousVersion = prev.split("\n").find(e => {
    return e.toLowerCase().includes('"version"');
  });
  const nextVersion = curr.split("\n").find(e => {
    return e.toLowerCase().includes('"version"');
  });
  return previousVersion === nextVersion;
};

something I hacked together after looking for a package that would do it. I found packages yes, but many of them also automated pushing back to git or publishing on npm etc.

All I want is if I've forgotten to bump any version at all, that the patch increments once with each commit.

Maybe future enhancement: accept a cli arg to increment the minor or major version instead. (Could be left as a precommit hook because the only time it'll change your file is if the version was untouched since the last commit.)