[Storage] Workaround to avoid duplicated 'content-length' headers on HTTP requests [storage-file]

[kinelski]

Both SDK and Axios module add a content-length header to HTTP requests. This workaround fixes this duplicated header issue while axios/axios#2107 is not solved.

A similar PR "fixed" the same problem in the storage-queue package (#2422). A different approach is being adopted this time because the previous "fix" wouldn't be enough to avoid the bug in storage-file.

The Axios HTTP adapter won't always include its own Content-Length header: when the request body is a stream, the header is not added. The piece of code responsible for this behavior:

if (data && !utils.isStream(data)) {
  if (Buffer.isBuffer(data)) {
    // Nothing to do...
  } else if (utils.isArrayBuffer(data)) {
    data = Buffer.from(new Uint8Array(data));
  } else if (utils.isString(data)) {
    data = Buffer.from(data, 'utf-8');
  } else {
    return reject(createError(
      'Data after transformation must be a string, an ArrayBuffer, a Buffer, or a Stream',
      config
    ));
  }


  // Add Content-Length header if data exists
  headers['Content-Length'] = data.length;
}

We need to make sure to remove the content-length header from the SDK requests only when necessary.

There are two possible scenarios we need to pay attention to:

• When the request body is a function: this function will be called by ms-rest-js to retrieve the stream body.

    let axiosBody =
      // Workaround for https://github.com/axios/axios/issues/755
      // tslint:disable-next-line:no-null-keyword
      typeof httpRequestBody === "undefined" ? null :
      typeof httpRequestBody === "function" ? httpRequestBody() :
      httpRequestBody;

This scenario is commonly triggered in Highlevel tests, since most of them make use of streams to upload files to Azure.

• When the request makes use of a progress event: ms-rest-js creates a stream to use as the request body in this case.

    const onUploadProgress = httpRequest.onUploadProgress;
    if (onUploadProgress && axiosBody) {
      let loadedBytes = 0;
      const uploadReportStream = new Transform({
        transform: (chunk: string | Buffer, _encoding, callback) => {
          loadedBytes += chunk.length;
          onUploadProgress({ loadedBytes });
          callback(undefined, chunk);
        }
      });
      if (isReadableStream(axiosBody)) {
        axiosBody.pipe(uploadReportStream);
      } else {
        uploadReportStream.end(axiosBody);
      }
      axiosBody = uploadReportStream;
    }

When any of the aforementioned scenarios happens, Axios won't include its own Content-Length header and we must keep ours.

[XiaoningLiu]

LGTM Thanks for your investigation!