Exception thrown in readline.createInterface with input stream

[ww9rivers]

• Version: v13.3.0
• Platform: Linux localhost 4.15.0-64-generic The README is oriented towards Node #73-Ubuntu SMP Thu Sep 12 13:16:13 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
• Subsystem:

I have a piece of code that reads a text file directly from a .tar.gz archive. The code started to throw an exception with Node v13.3.0.

Debugging the code, I found that, when the execution reached this point (line 446 in readline.js):

Interface.prototype._normalWrite = function(b) {
  if (b === undefined) {
    return;
  }
  let string = this._decoder.write(b); // <<<<
  if (this._sawReturnAt &&
      DateNow() - this._sawReturnAt <= this.crlfDelay) {
    string = string.replace(/^\n/, '');
    this._sawReturnAt = 0;
  }

the this._decoder was undefined.

That function was invoked when a ondata handler was set on line 223:

  if (!this.terminal) {
    function onSelfCloseWithoutTerminal() {
      input.removeListener('data', ondata);
      input.removeListener('end', onend);
    }

    input.on('data', ondata);
    input.on('end', onend);
    self.once('close', onSelfCloseWithoutTerminal);
    this._decoder = new StringDecoder('utf8');
  } else {

It seems that the line of code that sets this._decoder should be moved up 3 lines.

Does that make sense?

[BridgeAR]

@ww9rivers would you be so kind and post a minimal code piece with which it's possible to trigger the error?
It would also be great if you could check in what Node.js version the behavior changed. I can not find anything in the v13.3.0 release that should have impacted this, so I guess it either never worked or it broke in a former version.

[ww9rivers]

@ww9rivers would you be so kind and post a minimal code piece with which it's possible to trigger the error?

I have just put that in a gist:
https://gist.github.com/ww9rivers/5cd5343951f2ac0e966bf6c19c5f96ee

Thank you for the quick response! I was previously using a version 10 release, I believe. But I am not sure what the exact version was.

Edit: I edited the gist and add an archive file below:
tarball.tar.gz

Wonder if the exception has something to do with the use of Promise. I created another test, which is in the tarball, with Promise removed. That works OK.

[mscdex]

It's better to post the code here instead of an external link in case the external link dies at some point.

FWIW here is the code:

const fs = require('fs');
const readline = require('readline');
const util = require('util');
const tar = require('tar');
const zlib = require('zlib');
const test = require("tap").test;


function get_nsconf (archive, nsconf) {
        return new Promise((resolve, reject) => {
                if (!nsconf) { nsconf = '/nsconfig/ns.conf' }
                console.debug('----> Parsing NetScaler backup: '+archive);
                fs.createReadStream(archive).on('error', console.error)
                        .pipe(zlib.createUnzip())
                        .pipe(new tar.Parse())
                        .on('entry', entry => {
                                if (entry.path.endsWith(nsconf)) {
                                        if ('File' !== entry.type) {
                                                throw new Error('Wrong type for entry: '+nsconf+' : '+entry.type);
                                        }
                                        resolve({tar: archive, entry: entry});
                                } else {
                                        entry.resume();
                                }
                        })
        });
}

test('NetScaler config read test', t => {
        const archive = './tarball.tar.gz';
        const nsconf = 'tap-tar.js';
        get_nsconf(archive, nsconf).then(nsc => {
                let count = 0;
                // processing nsc as resolved by get_nsconf():
                console.debug('----> Found: '+nsc.entry.path);
                t.ok(nsc.tar == archive);
                t.ok(nsc.entry != undefined);
                readline.createInterface({
                        input: nsc.entry
                }).on('line', line => {
                        count++
                        console.log(line);
                        t.ok(null !== line && undefined !== line);
                }).on('close', () => {
                        console.log('----> File closed. Line count = '+count);
                        t.end();
                });
                console.debug('----> Closing file. Line count = '+count);
        }).catch(err => {
                console.log('Error: ', err, '\n', util.inspect(err.stack));
        });
});

[ww9rivers]

Thanks! I think I have two problems in the test above: The use of Promise is one. But the question I asked in the initial issue report is still valid.

So I created 3 tests, all in the tarball attached below. The tap-read.js is basically the same as the test posted above, which throws an error when run with Node v12.13.1. The other 2 tests work.

I cloned Node source and made the changed I suggested in the initial post above, tap-read.js still does not work but no longer throws an error either.
tarball.tar.gz

[BridgeAR]

@ww9rivers would you be so kind and reduce your test case to Node.js core code only? Right now there are still multiple node modules involved. It should be possible to see if it is indeed a Node.js bug or not.

[antsmartian]

@ww9rivers Could you please provide us a sample with only Node.js core code involved as @BridgeAR mentioned. That will help us to provide more information about the issue.

[RedYetiDev]

@ww9rivers Could you please provide us a sample with only Node.js core code involved as @BridgeAR mentioned. That will help us to provide more information about the issue.

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