When Babel cache gets too big, an exception "TypeError: Method Uint8Array.length called on incompatible receiver" is thrown from fs.writeFileSync

[sompylasar]

This issue: #2678 (Babel cache errors when it gets too big)
was improperly fixed via this commit: 8ffc701
which worked around the original error but introduced a different error:

TypeError: Method Uint8Array.length called on incompatible receiver [object Object]
    at Buffer.get length (native)
    at Object.fs.writeFileSync (fs.js:1161:20)
    at save (/__CENSORED__/node_modules/babel-register/lib/cache.js:45:16)
    at nextTickCallbackWith0Args (node.js:436:9)
    at process._tickDomainCallback (node.js:406:13)

which gets thrown from fs.writeFileSync: https://github.com/nodejs/node/blob/v4.7.0/lib/fs.js#L1161

The error is caused by erroneously passing an Object ({}) instead of a String, Buffer or UInt8Array into fs.writeFileSync. https://nodejs.org/api/fs.html#fs_fs_writefilesync_file_data_options

The error as of now is in the latest master of babel/packages/babel-register:

babel/packages/babel-register/src/cache.js

Line 26 in 9c2794d

fs.writeFileSync(FILENAME, serialised);

/**
 * Write stringified cache to disk.
 */

export function save() {
  let serialised = {};  //<<<<< `serialized` is initialized with a non-serialized `{}`, i.e. `Object`.
  try {
    serialised = JSON.stringify(data, null, "  ");
  } catch (err) {
    if (err.message === "Invalid string length") {
      err.message = "Cache too large so it's been cleared.";
      console.error(err.stack);
      //<<<<< No control flow interruption happens here, fall through, `serialized === {}`.
    } else {
      throw err;
    }
  }
  mkdirpSync(path.dirname(FILENAME));
  fs.writeFileSync(FILENAME, serialised);  //<<<<< `{}` in `serialized` got to here.
}

Proposed change:

  export function save() {
-   let serialised = {};
+   let serialised = "{}";

[babel-bot]

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so it's possible this won't be addressed swiftly.

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[xtuc]

Good catch 👍

This would have catch using Flow annotations I think. I will make a PR for that.

[xtuc]

Closed in #5260. Feel free to reopen this issue.