Another bug in 2.15

[StasD]

Issues a warning:

Sending `DownloadBegin` with no listeners registered.

when I do

  let {promise} = fs.downloadFile({fromUrl, toFile});

[StasD]

Going back to 2.14 for now...

[itinance]

@StasD
So, it's just a warning and not a serious error? Will definitely have a look at it. I'm just asking to identify if its a serious issue breaking downloadFile

[StasD]

It's a warning, but it is displayed very prominently when I run the program in iOS simulator, and I have to press "Dismiss All" before I can use the program in the simulator again.
Just noticed there is another warning about "DownloadProgress" listener.
So, these are very annoying and also not necessary. I don't care about those listeners whatsoever, and if I did, I would have found how to use them in the documentation.
It would be great if you remove these warnings or downgrade them so that they don't show up as prominently in the simulator. Thanks.

[itinance]

I think it has something to do with this PR: #752

[itinance]

@jnpdx can you have a look at this issue here pls? There is little chance that it was introduced with #752

[StasD]

Also I use react-native-navigation component, which requires AppDelegate.m to be modified: here. I took a quick look at "Files changed" section of that PR and thought this information could be relevant...

[jnpdx]

@itinance

It looks like event listeners are only registered in the event that a begin parameter is passed. So, it seems that the options would be:

1. Register an empty callback with the emitter in the event that no begin parameter was sent.
2. Only send events with the emitter if the begin or similar parameters have been registered.

#1 seems like a better option because #2 will require changing the signature of the native methods in order to implement. I'd be happy to submit a PR for #1.

However, I have a secondary issue, which is I can't actually seem to replicate this issue, whether I pass callbacks or not.

@StasD -- what versions of React Native and iOS are you on?

[StasD]

All latest: RN 0.61.2, iOS 13.1 in the simulator.

[StasD]

@itinance Also, please check the above link from react-native-navigator documentation. I have a suspicion that the way how AppDelegate.m is modified might have something to do with this. Though I might be wrong.

[jnpdx]

@StasD Ah, I see, this issue only appears for me in certain scenarios (eg other listeners have never been registered). Since I was testing uploads as well, I didn't see it.

It looks like the current hot fix would be to pass () => {} for the begin parameter when you call downloadFile. (@StasD can you confirm that works with your setup as a temporary fix?)

That also supports my first fix idea I suggested above. I'll submit a PR unless @itinance has an issue with that method of fixing it.

[jnpdx]

@StasD alternately, try with this fork, which will become my PR if it works: https://github.com/jnpdx/react-native-fs#7558d9f

[StasD]

Yes, if I pass () => {} for the begin parameter, warnings disappear. Interestingly, the warning for progress disappears too...

[jnpdx]

@StasD yeah, I think that's why I didn't see this issue at first the emitter is really inconsistent about when it complains about things. I'll submit my patch as a PR.