Pause and resume (In a quick succession) gets you lot of exceptions and an infinite loop

[varunsharma27]

Doing pause and resume (In a quick succession) on demo gets you lot of exceptions :-

papaparse.js:733 Uncaught DOMException: Failed to execute 'readAsText' on 'FileReader': The object is already busy reading Blobs.
    at FileStreamer._readChunk (https://www.papaparse.com/resources/js/papaparse.js:733:21)
    at FileStreamer._nextChunk (https://www.papaparse.com/resources/js/papaparse.js:722:10)
    at FileStreamer.ChunkStreamer.parseChunk (https://www.papaparse.com/resources/js/papaparse.js:538:10)
    at FileStreamer._chunkLoaded (https://www.papaparse.com/resources/js/papaparse.js:743:9)
    at FileReader.<anonymous> (https://www.papaparse.com/resources/js/papaparse.js:1800:25)
FileStreamer._readChunk	@	papaparse.js:733
FileStreamer._nextChunk	@	papaparse.js:722
ChunkStreamer.parseChunk	@	papaparse.js:538
FileStreamer._chunkLoaded	@	papaparse.js:743
(anonymous)	@	papaparse.js:1800
load (async)		
FileStreamer.stream	@	papaparse.js:710
CsvToJson	@	papaparse.js:265
parseNextFile	@	papaparse.js:163
$.fn.parse	@	papaparse.js:113
(anonymous)	@	demo.js:103
dispatch	@	jquery.min.js:3
r.handle	@	jquery.min.js:3

And if you choose to handle them, like this :-

function stepFn(results, parser)
{
	stepped++;
	if (results)
	{
		parser.pause();
		try{
		parser.resume();
		} catch (e) {
			console.log(e);
		}
		if (results.data){
			array2 = array2.concat(results.data); // Just to check the data
			rowCount += results.data.length;
		}
		if (results.errors)
		{
			errorCount += results.errors.length;
			firstError = firstError || results.errors[0];
		}
	}
}

Then you get into an infinite loop with the same data.

It appears that resume should be waiting for previous pause to halt the parsing before continuing again.
It appears this wasn't the case before since Issue #321 talks about doing this to produce another bug (Cursor related).
I am using :-
Papa.LocalChunkSize = 10485
Otherwise you get :-

RangeError: Maximum call stack size exceeded
    at FileStreamer.ChunkStreamer.parseChunk (papaparse.js:491)
    at ParserHandle.resume (papaparse.js:1078)
    at stepFn (demo.js:212)
    at ParserHandle._config.step (papaparse.js:1017)
    at doStep (papaparse.js:1651)
    at Parser.parse (papaparse.js:1561)
    at ParserHandle.parse (papaparse.js:1058)
    at FileStreamer.ChunkStreamer.parseChunk (papaparse.js:489)
    at ParserHandle.resume (papaparse.js:1078)
    at stepFn (demo.js:212)

[econic]

Having the same issue after trying to pause and resume the parser within each step

[yew2993]

I found that calling pause and resume in a promise chain resolved this issue for me.

function step(fn) {
  return (results, parser) => {
    Promise.resolve().then(() => {
      parser.pause();
      fn(results);
    }).then(() => {
      parser.resume();
    })
  }
}

[varunsharma27]

@yew2993 The issue is fixed in the PR, currently waiting merge. It happens because resume is not waiting for previous pause to halt the parsing before continuing again.

[pokoli]

I've merged the PR so it should work correctly on master