nixpkgs/pkgs/development/tools/yarn2nix-moretea/yarn2nix/lib/fixPkgAddMissingSha1.js

const https = require("https");
const crypto = require("crypto");

// TODO:
// make test case where getSha1 function is used, i.e. the case when resolved is without sha1?
// consider using https://github.com/request/request-promise-native

function getSha1(url) {
  return new Promise((resolve, reject) => {
    https.get(url, res => {
      const { statusCode } = res;
      const hash = crypto.createHash("sha1");

      if (statusCode !== 200) {
        const err = new Error(`Request Failed.\nStatus Code: ${statusCode}`);

        // consume response data to free up memory
        res.resume();

        reject(err);
      }

      res.on("data", chunk => {
        hash.update(chunk);
      });

      res.on("end", () => {
        resolve(hash.digest("hex"));
      });

      res.on("error", reject);
    });
  });
}

// Object -> Object
async function fixPkgAddMissingSha1(pkg) {
  // local dependency

  if (!pkg.resolved) {
    console.error(
      `yarn2nix: can't find "resolved" field for package ${pkg.nameWithVersion}, you probably required it using "file:...", this feature is not supported, ignoring`
    );
    return pkg;
  }

  const [url, sha1] = pkg.resolved.split("#", 2);

  if (sha1 || url.startsWith("https://codeload.github.com")) {
    return pkg;
  }

  // if there is no sha1 in resolved url
  // (this could happen if yarn.lock was generated by older version of yarn)
  // - request it from registry by https and add it to pkg
  const newSha1 = await getSha1(url);

  return {
    ...pkg,
    resolved: `${url}#${newSha1}`
  };
}

module.exports = fixPkgAddMissingSha1;