Check commit messages in PRs for Node.js repository

node-check-commit-messages.js

javascript: {
  const validPathname = /^\/nodejs\/node\/pull\/\d+(?:\/commits)?$/;

  const TITLE_MAX_LENGTH = 50;
  const LINE_MAX_LENGTH = 72;

  const titleFormat = /^([\d_a-z ,-]+)\b: ([a-z'-]+\b)?/;
  const lineWithURLFormat = /^(Fixes|Refs?): (https?:)?/;

  const LOG_DELIMITER_LENGTH = 20;

  const loaderBar = document.querySelector('#js-pjax-loader-bar');

  const observer = new MutationObserver((mutations) => {
    mutations.forEach((mutation) => {
      if (mutation.oldValue.includes('is-loading') &&
                   validPathname.test(location.pathname)) check();
    });
  });

  observer.observe(loaderBar,
    { attributes: true, attributeOldValue: true, attributeFilter: ['class'] }
  );

  check();

  function check() {
    let OK = 0;
    let notOK = 0;

    const allErrors = [];

    const commitLinks = [...document.body.querySelectorAll('a[href].message')];

    const hrefSeen = [];

    commitLinks.forEach((commitLink, commitNumber) => {
      const href = commitLink.href;
      if (hrefSeen.includes(href)) return;
      hrefSeen.unshift(href);

      const commitErrors = [];

      const lines = commitLink.title.split('\n');
      const title = lines.shift();

      const [, titlePrefix, lcVerb] = title.match(titleFormat) || [];
      const titleLength = [...title].length;

      if (!titlePrefix) {
        commitErrors.push('Begin commit title with subsystem prefix');
      }
      if (!lcVerb) {
        commitErrors.push('Use lower case imperative verb after subsystem prefix');
      }
      if (titleLength > TITLE_MAX_LENGTH) {
        commitErrors.push(
          `Keep commit title length within ${
            TITLE_MAX_LENGTH} characters (currently ${titleLength})`
        );
      }

      if (lines.length && lines[0] !== '') {
        commitErrors.push('Insert empty line after commit title');
      }

      let lineNumber = 1;
      lines.forEach((line) => {
        lineNumber++;

        const lineLength = [...line].length;
        if (lineLength > LINE_MAX_LENGTH) {
          commitErrors.push(
            `Keep line length within ${
              LINE_MAX_LENGTH} characters: line ${
                lineNumber} length is ${lineLength}:\n${line}`
          );
        }

        const [, linePrefix, protocol] = line.match(lineWithURLFormat) || [];
        if (linePrefix && !protocol) {
          commitErrors.push(
            `Use full URL with 'Fixes:' and 'Refs:': line ${lineNumber}:\n${line}`
          );
        }
      });

      if (!commitErrors.length) {
        OK++;
        commitLink.style.backgroundColor = 'LightGreen';
      } else {
        notOK++;
        commitLink.style.backgroundColor = 'LightCoral';

        const errorMessage = commitErrors.map(error => `* ${error}`).join('\n\n');
        allErrors.push(`Commit ${commitNumber + 1} (${title}):\n\n${errorMessage}`);

        const errorInfo = getOrCreate(
          'span', '.node-check-commit-messages-error', commitLink.parentNode, commitLink.nextSibling
        );
        errorInfo.title = errorMessage;
        errorInfo.textContent = '!';
        errorInfo.setAttribute('style',
          'padding: 0px 3px 0px 3px; margin: 0px 3px 0px 3px; background-color: LightCoral;'
        );
      }
    });

    const results = commitLinks.length ?
      `OK: ${OK}${notOK ? `\nNot OK: ${notOK}` : ''}`
      :
      'No commits found.';

    const parent = document.querySelector('#discussion_bucket, #commits_bucket');
    const resultsInfo = getOrCreate('pre', '#node-check-commit-messages-results', parent);
    resultsInfo.textContent = results;
    resultsInfo.setAttribute('style',
      `position: fixed; top: 0px; left: 0px; z-index: 10000; background-color: ${
        notOK ? 'LightCoral' : OK ? 'LightGreen' : 'LightGray'
      }; padding: 3px;`
    );

    if (notOK) {
      resultsInfo.style.cursor = 'pointer';
      resultsInfo.title = 'click to copy full log';
      const copyImg = getOrCreate(
        'img', '#node-check-commit-messages-results-copy-img', resultsInfo
      );
      copyImg.alt = allErrors.join(`\n\n${'-'.repeat(LOG_DELIMITER_LENGTH)}\n\n`);
      copyImg.src =
        'data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==';
      resultsInfo.addEventListener('click', copyLog);
    }
  }

  function getOrCreate(tag, attr, parent = document.body, nodeToInsertBefore = null) {
    let elem = parent.querySelector(`${tag}${attr}`);
    if (!elem) {
      elem = document.createElement(tag);
      elem[attr.startsWith('#') ? 'id' : 'className'] = attr.slice(1);
      parent.insertBefore(elem, nodeToInsertBefore);
    }
    return elem;
  }

  function copyLog(event) {
    const sel = window.getSelection();
    sel.removeAllRanges();
    const range = document.createRange();
    range.selectNode(event.target.querySelector('img'));
    sel.addRange(range);
    document.execCommand('copy');
    sel.removeAllRanges();
  }
}

Tampermonkey header example:

/******************************************************************************/
// ==UserScript==
// @name         Check Commits
// @namespace    vsemozhetbyt
// @description  Check commit messages in PRs for Node.js repository
// @version      1.0.0
// @include      https://github.com/nodejs/node/commits/master
// @include      https://github.com/nodejs/node/pull/*
// @exclude      https://github.com/nodejs/node/pull/*/files*
// @noframes     
// @grant        none
// @nocompat     Chrome
// ==/UserScript==
/******************************************************************************/