Using Electron's net module, the aim is to fetch a resource and, once the response is received, to pipe it to a writeable stream like so:
const stream = await fetchResource('someUrl');
stream.pipe(fs.createWriteStream('./someFilepath'));
As simplified implementation of fetchResource
is as follows:
import { net } from 'electron';
async function fetchResource(url) {
return new Promise((resolve, reject) => {
const data = [];
const request = net.request(url);
request.on('response', response => {
response.on('data', chunk => {
data.push(chunk);
});
response.on('end', () => {
// Maybe do some other stuff with data...
});
// Return the response to then pipe...
resolve(response);
});
request.end();
});
}
The response ends up being an instance of IncomingMessage, which implements a Readable Stream interface according to the node docs , so it should be able to be piped to a write stream.
The primary issue is there ends up being no data in the stream that get's piped through 😕
Answering my own question, but the issue is reading from multiple sources: the resolved promise and the 'data'
event. The event listener source was flushing out all the data before the resolved promise could get to it.
A solution is to fork the stream into a new one that won't compete with the original if more than once source tries to pipe from it.
import stream from 'stream';
// ...make a request and get a response stream, then fork the stream...
const streamToResolve = response.pipe(new stream.PassThrough());
// Listen to events on response and pipe from it
// ...
// Resolve streamToResolve and separately pipe from it
// ...
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