[run] repl/stdin to remote issues

[rwaldron]

Easily reproduced with:

var repl = require('repl');
var connections = 0;

repl.start({
  prompt: 'Node.js via stdin> ',
  input: process.stdin,
  output: process.stdout
});

Actual:

$ t2 run repl.js
INFO Looking for your Tessel...
INFO Connected to bishop.
INFO Building project.
INFO Writing project to RAM on bishop (96.256 kB)...
INFO Deployed.
INFO Running repl.js...
Node.js via stdin> 1

Expected:

$ t2 run repl.js
INFO Looking for your Tessel...
INFO Connected to bishop.
INFO Building project.
INFO Writing project to RAM on bishop (96.256 kB)...
INFO Deployed.
INFO Running repl.js...
Node.js via stdin> 1
1
Node.js via stdin> 1 + 2
3
Node.js via stdin>

If you run with just node.js:

$ node repl.js
Node.js via stdin> 1
1
Node.js via stdin> 1 + 2
3
Node.js via stdin>

[johnnyman727]

Wow, I didn't know the repl lib existed. That's cool!

The problem is that we aren't piping stdin of the host to the process. It can be fixed by adding the following line to where the JS file is executed (within the run and push functions):

process.stdin.pipe(remoteProcess.stdin);

(assuming remoteProcess is the name of the process variable returned from exec)

[rwaldron]

I'll play around with it, or @HipsterBrown can dig in

[wyze]

I tried playing around with this one for a little bit tonight. Using what @johnnyman727 suggested above, this was the output:

~/Projects/personal/t2-repl 8s
❯ t2 run repl.js
INFO Looking for your Tessel...
INFO Connected to t2-testing.
INFO Building project.
INFO Writing project to RAM on t2-testing (3.072 kB)...
INFO Deployed.
INFO Running repl.js...
Node.js via stdin> 1
1
1
Node.js via stdin> 1 + 2
1 + 2
3
Node.js via stdin>

So, I pressed on and modified remoteProcess.stdout instead of a straight pipe to the CLI, I was filtering based on the buffer length. Seems kind of hacky/dirty so I didn't open a PR. I can open a PR if interested, but here was the output after my additional changes:

~/Projects/personal/t2-repl 31s
❯ t2 run repl.js
INFO Looking for your Tessel...
INFO Connected to t2-testing.
INFO Building project.
INFO Writing project to RAM on t2-testing (3.072 kB)...
INFO Deployed.
INFO Running repl.js...
Node.js via stdin> 1
1
Node.js via stdin> 1 + 2
3
Node.js via stdin>

[johnnyman727]

@wyze thanks for trying it out!

So on a hunch, I checked this out as well. It looks like the stdin duplication does not happen if you t2 run repl.js --usb. It's only an issue with SSH connections.

That's because the way the ssh2 library works, it spits out a Channel object once exec is called. A Channel is a TransformStream with the Readable side as stdout and the Writeable side as stdin.

In order to have the same remoteProcess.stdin, remoteProcess.stdout, remoteProcess.stderr API as the USBConnections, we set remoteProcess.stdin and remoteProcess.stdout to the same object. That means when we write to remoteProcess.stdin, it's also getting written to remoteProcess.stdout somehow and then piped back to process.stdout.

I'm not sure what the best solution is here because I don't really understand why there seems to be a feedback loop between remoteProcess.stdin and remoteProcess.stdout.

[johnnyman727]

BTW, this would be a really useful feature to add to the CLI (t2 repl) especially if we can get bash history working with it.

[JRJurman]

I'm trying to get similar functionality in my own project. What edits should I be making, or is there a PR to introduce this?

[rwaldron]

@JRJurman

I'm trying to get similar functionality in my own project. What edits should I be making, or is there a PR to introduce this?

Do you mean for your program to produce an interactive terminal/repl/readline when it's run? If yes, then that is already available, but only via LAN connection (which is over SSH).

• cb710fe
• c37ff9d
• 90eac0e

[boneskull]

I'm running into this. I want to interact with a REPL (or more specifically, something using readline, but can only do so if connecting via LAN.

I would attempt to fix this on my own, but I don't understand what was happening before @rwaldron's list of changesets (in other words, what misbehavior to avoid).