get-package-json.ts

/**
 * refer: https://github.com/mysticatea/eslint-plugin-node/blob/f45c6149be7235c0f7422d1179c25726afeecd83/lib/util/get-package-json.js
 */

import fs from "fs"
import path from "path"
import { createCache } from "./cache"

type PackageJson = Record<string, any> & { filePath: string }

const isRunOnBrowser = !fs.readFileSync
const cache = createCache<PackageJson | null>()

/**
 * Reads the `package.json` data in a given path.
 *
 * Don't cache the data.
 *
 * @param dir The path to a directory to read.
 * @returns The read `package.json` data, or null.
 */
function readPackageJson(dir: string): PackageJson | null {
  if (isRunOnBrowser) return null
  const filePath = path.join(dir, "package.json")
  try {
    const text = fs.readFileSync(filePath, "utf8")
    const data = JSON.parse(text)

    if (typeof data === "object" && data !== null) {
      data.filePath = filePath
      return data
    }
  } catch (_err) {
    // do nothing.
  }

  return null
}

/**
 * Gets a `package.json` data.
 * The data is cached if found, then it's used after.
 * @param startPath A file path to lookup.
 * @returns A found `package.json` data or `null`.
 *      This object have additional property `filePath`.
 */
export function getPackageJson(startPath = "a.js"): PackageJson | null {
  if (isRunOnBrowser) return null
  const startDir = path.dirname(path.resolve(startPath))
  let dir = startDir
  let prevDir = ""
  let data = null

  do {
    data = cache.get(dir)
    if (data) {
      if (dir !== startDir) {
        cache.set(startDir, data)
      }
      return data
    }

    data = readPackageJson(dir)
    if (data) {
      cache.set(dir, data)
      cache.set(startDir, data)
      return data
    }

    // Go to next.
    prevDir = dir
    dir = path.resolve(dir, "..")
  } while (dir !== prevDir)

  cache.set(startDir, null)
  return null
}