Encoder for GIF provides a Promise to getBuffer when a string, Buffer, or Uint8Array is expected

[stevezac-osu]

Fixing Issue 980: The 'chunk' argument must be of type string or an Instance of Buffer or Uint8Array. Received an instance of Promise.

What's Changing and Why

On jimp/packages/core/src/utils/image-bitmap.js getBuffer(mime, cb) function, the method is intended to provide a string or a buffer to a callback function so that the callback can consume such buffer (typically with the Write function).

However, occasionally the following error will occur ( see also #980 ):

internal/streams/writable.js:285
      throw new ERR_INVALID_ARG_TYPE(
      ^

TypeError [ERR_INVALID_ARG_TYPE]: The "chunk" argument must be of type string or an instance of Buffer or Uint8Array. Received an instance of Promise
    at new NodeError (internal/errors.js:322:7)
    at WriteStream.Writable.write (internal/streams/writable.js:285:13)
    at WriteStream.<anonymous> (/home/zachs1590/cs464-jimp-testing/node_modules/@jimp/core/dist/index.js:462:16)
    at WriteStream.emit (events.js:400:28)
    at internal/fs/streams.js:340:12
    at FSReqCallback.oncomplete (fs.js:180:23) {
  code: 'ERR_INVALID_ARG_TYPE'

I traced the issue back to the fact that one of the encoders, the GIF encoder, consistently returns a promise rather than a string or a buffer response. See jimp/packages/type-gif/src/index.js line 34.

Rather than solve this issue at the GIF encoder (if that could be solved at all), it seemed like a better idea to make the get buffer function more robust by permitting encoders to return a promise as a valid data type and handle such a response gracefully.

Accordingly, on jimp/packages/core/src/utils/image-bitmap.js getBuffer(mime, cb), I have added

  if (this.constructor.encoders[mime]) {
    const buffer = this.constructor.encoders[mime](this);
    //Typically, buffers return a string or map.  However, the gif library "gifwrap" seemingly returns promises.
    if(buffer instanceof Promise){
      //trigger the callback when the promise has been resolved
      buffer.then((buff) => {
        cb.call(this, null, buff);
      })
    } else {
      cb.call(this, null, buffer);
    }

What else might be affected

n/a

[stevezac-osu]

Please note -- I think this solves not only #980, but also #1000 and #1056

[jasonz1987]

please merge this pr.

[jbwebtech]

@stevezac-osu thank you for finding (and fixing!) the issue many of us are experiencing. I implemented your change locally, and it worked great! 👍🎉

[github-actions]

🚀 PR was released in v0.22.10 🚀