statsUtils.js

const { createWriteStream } = require("node:fs");
const { Readable } = require("node:stream");
const { pipeline } = require("node:stream/promises");

/** @typedef {import("./BundleAnalyzerPlugin").EXPECTED_ANY} EXPECTED_ANY */
/** @typedef {import("webpack").StatsCompilation} StatsCompilation */

class StatsSerializeStream extends Readable {
  /**
   * @param {StatsCompilation} stats stats
   */
  constructor(stats) {
    super();
    this._indentLevel = 0;
    this._stringifier = this._stringify(stats);
  }

  get _indent() {
    return "  ".repeat(this._indentLevel);
  }

  _read() {
    let readMore = true;

    while (readMore) {
      const { value, done } = this._stringifier.next();

      if (done) {
        this.push(null);
        readMore = false;
      } else {
        readMore = this.push(value);
      }
    }
  }

  /**
   * @param {EXPECTED_ANY} obj obj
   * @returns {Generator<string, undefined, unknown>} stringified result
   * @private
   */
  *_stringify(obj) {
    if (
      typeof obj === "string" ||
      typeof obj === "number" ||
      typeof obj === "boolean" ||
      obj === null
    ) {
      yield JSON.stringify(obj);
    } else if (Array.isArray(obj)) {
      yield "[";
      this._indentLevel++;

      let isFirst = true;
      for (let item of obj) {
        if (item === undefined) {
          item = null;
        }

        yield `${isFirst ? "" : ","}\n${this._indent}`;
        yield* this._stringify(item);
        isFirst = false;
      }

      this._indentLevel--;
      yield obj.length ? `\n${this._indent}]` : "]";
    } else {
      yield "{";
      this._indentLevel++;

      let isFirst = true;
      const entries = Object.entries(obj);
      for (const [itemKey, itemValue] of entries) {
        if (itemValue === undefined) {
          continue;
        }

        yield `${isFirst ? "" : ","}\n${this._indent}${JSON.stringify(itemKey)}: `;
        yield* this._stringify(itemValue);
        isFirst = false;
      }

      this._indentLevel--;
      yield entries.length ? `\n${this._indent}}` : "}";
    }
  }
}

/**
 * @param {StatsCompilation} stats stats
 * @param {string} filepath filepath file path
 * @returns {Promise<void>}
 */
async function writeStats(stats, filepath) {
  await pipeline(new StatsSerializeStream(stats), createWriteStream(filepath));
}

module.exports = { StatsSerializeStream, writeStats };