I'm writing a custom middleware that needs to send files. (I'm porting it from Express to Koa, actually.)

I'd like to reuse the capability from your middleware to send a specific file.

Here's a simplified example:

import { Middleware } from "koa";
import server from "koa-files";
import path from "node:path";
import fs from "node:fs";

export function myMiddleware(): Middleware {
  return (context, next) => {
    const rootPath = "/home/user/app/files";
    const fileName = "folder/file.jpg";
  
    console.log("exists", fs.existsSync(path.join(rootPath, fileName))); // true
  
    context.path = fileName; // I've also tried `context.url = filename` and `context.path = "/"+filename`
  
    server(rootPath)(context, next);
  };
}

I see "exists: true" on the console, so I know the file exists.

But the response on the page is always just "Not found".

I know it's probably unusual to create and call middleware from within another middleware - but the library doesn't export a function to just send a specific file on demand, and since my rootPath can't be determined at startup, I have to create and run the middleware every time. That would probably be fine, since your middleware doesn't do any heavy initialization.

But it just doesn't work. Any idea why?

Hi, great work on this. It seems much cleaner than koa-range and it's nice to see multipart support.

This is less of an issue and more of a question, or potentially a note that could be added to the docs, but I've been getting these connection reset errors trying to play videos from a node server using Chrome 81:

Error: write ECONNRESET
      at WriteWrap.onWriteComplete [as oncomplete] (internal/stream_base_commons.js:92:16)
      at handleWriteReq (internal/stream_base_commons.js:51:26)
      at writeGeneric (internal/stream_base_commons.js:143:15)
      at TLSSocket.Socket._writeGeneric (net.js:780:11)
      at TLSSocket.Socket._write (net.js:792:8)
      at doWrite (_stream_writable.js:441:12)
      at clearBuffer (_stream_writable.js:580:7)
      at TLSSocket.Writable.uncork (_stream_writable.js:336:7)
      at ServerResponse.OutgoingMessage.uncork (_http_outgoing.js:244:17)
      at connectionCorkNT (_http_outgoing.js:698:8)

This happens with every range request implementation I've tried, including both this and koa-range. Fortunately, it doesn't seem to be affecting playback at all.

I noticed you have an error event handler in your example that silences these, among others:

function httpError(error) {
  return /^(EOF|EPIPE|ECANCELED|ECONNRESET|ECONNABORTED)$/i.test(error.code);
}

// ...

// Listen error event
app.on('error', error => !httpError(error) && console.error(error));

So, my question is, what is the reasoning behind this, aside from just not clogging up logs with these things? Do we know why these are happening, and whether or not they might be a problem in a production environment?

It's been really hard to find information about this through either Google or Stack Overflow. Would you mind pointing me in the right direction, and maybe allowing me to add some notes about the answers I find to your README, for the sake of others?