Function parseChangelog

scripts/changes/changes.ts:620–649

* Parses a package's CHANGELOG.md and returns all version entries

(packageDirName: string)

 * Parses a package's CHANGELOG.md and returns all version entries
 */
function parseChangelog(packageDirName: string): AllChangelogEntries | null {
  let changelogPath = getPackageFile(packageDirName, "CHANGELOG.md");

  if (!fileExists(changelogPath)) {
    return null;
  }

  let changelog = readFile(changelogPath);
  let parser = /^## ([a-z\d.-]+)(?: \(([^)]+)\))?$/gim;

  let result: AllChangelogEntries = {};

  let match;
  while ((match = parser.exec(changelog))) {
    let [, versionString, dateString] = match;
    let lastIndex = parser.lastIndex;
    let version = versionString.startsWith("v")
      ? versionString.slice(1)
      : versionString;
    let date = dateString ? new Date(dateString) : undefined;
    let nextMatch = parser.exec(changelog);
    let body = changelog
      .slice(lastIndex, nextMatch ? nextMatch.index : undefined)
      .trim();
    result[version] = { version, date, body };
    parser.lastIndex = lastIndex;
  }

  return result;
}

/**
 * Gets a specific version's entry from a package's CHANGELOG.md.