update-authors.mjs

#!/usr/bin/env node
// Usage: tools/update-authors.mjs [--dry]
// Passing --dry will redirect output to stdout rather than write to 'AUTHORS'.
import { spawn } from 'node:child_process';
import fs from 'node:fs';
import readline from 'node:readline';

class CaseIndifferentMap {
  _map = new Map();

  get(key) { return this._map.get(key.toLowerCase()); }
  has(key) { return this._map.has(key.toLowerCase()); }
  set(key, value) { return this._map.set(key.toLowerCase(), value); }
}

const log = spawn(
  'git',
  // Inspect author name/email and body.
  ['log', '--reverse', '--format=Author: %aN <%aE>\n%b'], {
    stdio: ['inherit', 'pipe', 'inherit']
  });
const rl = readline.createInterface({ input: log.stdout });

let output;
if (process.argv.includes('--dry'))
  output = process.stdout;
else
  output = fs.createWriteStream('AUTHORS');

output.write('# Authors ordered by first contribution.\n\n');

const mailmap = new CaseIndifferentMap();
{
  const lines = fs.readFileSync(new URL('../.mailmap', import.meta.url),
                                { encoding: 'utf8' }).split('\n');
  for (let line of lines) {
    line = line.trim();
    if (line.startsWith('#') || line === '') continue;

    const match = line.match(/^(?:([^<]+)\s+)?(?:(<[^>]+>)\s+)?(?:([^<]+)\s+)?(<[^>]+>)$/);
    if (match) {
      const [, replaceName, replaceEmail, originalName, originalEmail] = match;
      const key = originalName ? `${originalName}\0${originalEmail.toLocaleLowerCase()}` : originalEmail.toLowerCase();
      mailmap.set(key, {
        author: replaceName || originalName,
        email: replaceEmail || originalEmail,
      });
    } else {
      console.warn('Unknown .mailmap format:', line);
    }
  }
}

const previousAuthors = new CaseIndifferentMap();
{
  const lines = fs.readFileSync(new URL('../AUTHORS', import.meta.url),
                                { encoding: 'utf8' }).split('\n');
  for (let line of lines) {
    line = line.trim();
    if (line.startsWith('#') || line === '') continue;

    const match = line.match(/^([^<]+)\s+(<[^>]+>)$/);
    if (match) {
      const name = match[1];
      const email = match[2];
      if (previousAuthors.has(name)) {
        const emails = previousAuthors.get(name);
        emails.push(email);
      } else {
        previousAuthors.set(name, [email]);
      }
    } else {
      console.warn('Unknown AUTHORS format:', line);
    }
  }
}

const seen = new Set();

// Support regular git author metadata, as well as `Author:` and
// `Co-authored-by:` in the message body. Both have been used in the past
// to indicate multiple authors per commit, with the latter standardized
// by GitHub now.
const authorRe =
  /(^Author:|^Co-authored-by:)\s+(?<author>[^<]+)\s+(?<email><[^>]+>)/i;
for await (const line of rl) {
  const match = line.match(authorRe);
  if (!match) continue;

  let { author, email } = match.groups;
  const emailLower = email.toLowerCase();

  const replacement =
    mailmap.get(author + '\0' + emailLower) || mailmap.get(emailLower);
  if (replacement) {
    ({ author, email } = { author, email, ...replacement });
  }

  if (seen.has(email)) {
    continue;
  }

  seen.add(email);
  output.write(`${author} ${email}\n`);
  const duplicate = previousAuthors.get(author);
  if (duplicate && !duplicate.includes(email)) {
    console.warn('Author name already in AUTHORS file. Possible duplicate:');
    console.warn(`  ${author} ${email}`);
  }
}

output.end('\n# Generated by tools/update-authors.mjs\n');