Function prependPathEntries

packages/cli-exec/src/envpath.ts:6–26

(
  pathValue: string,
  directories: string[]
)

 * Prepends path entries while preserving existing entries and order.
 */
export function prependPathEntries(
  pathValue: string,
  directories: string[]
): string {
  const pathParts = pathValue.split(path.delimiter).filter(Boolean);
  const prepended: string[] = [];

  for (const directory of directories) {
    if (!pathParts.includes(directory) && !prepended.includes(directory)) {
      prepended.push(directory);
    }
  }

  if (prepended.length === 0) {
    return pathValue;
  }

  return pathValue === '' || pathValue === path.delimiter
    ? `${prepended.join(path.delimiter)}${pathValue}`
    : [...prepended, pathValue].join(path.delimiter);
}

/**
 * Splits a PATH value into non-empty directory entries.