Add dumb mode support

[arichiardi]

Hello folks!

I am trying to call ts-node from inside an Emacs buffer and I see the color escape characters in there.
This problem already happened to me, in lumo specifically.

I had to enable "dumb" mode in there, so now readline support whatsoever, was wondering whether it could be done here as well.

Thanks and good job here!

[blakeembrey]

I'm not sure I understand the issue. Do you just want to disable colours? The only time, I believe, there's colour used is for the error title. You should be able to specify --no-color to disable that (https://www.npmjs.com/package/chalk#chalksupportscolor), but let me know if that doesn't work.

[arichiardi]

Yes I thought there was full readline support but I am trying --no-color now.

[arichiardi]

Unfortunately it is not a problem of colors, see the bottom how the command is launched:

[arichiardi]

I think I can workaround with NODE_NO_READLINE=1.

Edit: nope.

[blakeembrey]

So the issue is related to the REPL specifically? I'm not sure what I can do there, it's all standard node REPL functionality - maybe someone has asked on their issues. Do you have the same issue running node?

[arichiardi]

Not really an expert on this, but this is how it is solved in lumo.

[blakeembrey]

Since that's just an internal option to readline, I'm not sure how to interpret it. It looks like they overrode the line printing? I'm using REPL, so it's not exactly the same, but possibly I could change something (here: https://nodejs.org/api/repl.html#repl_customizing_repl_output) if I knew what the issue is. Can you share what exactly is broken? Is it the prompt, after you hit enter and it prints stuff out, everything?

[arichiardi]

You can see the print screen above for the error. That is what I see when I start it from within Emacs.
Apparently that is what he did, I am trying to understand as well 😀

[cspotcode]

Took a quick look and did some research. tl;dr if anything, we can add support for node's NODE_NO_READLINE env var, to more closely mimic the built-in REPL. Otherwise I'm not sure there's anything we should do here.

NodeJS internally does this when creating its REPL:
https://github.com/nodejs/node/blob/master/lib/internal/repl.js#L28-L30
https://github.com/nodejs/node/blob/master/lib/internal/repl.js#L50-L51

We do this: (slightly different)
https://github.com/TypeStrong/ts-node/blob/master/src/bin.ts#L345

https://www.gnu.org/software/emacs/manual/html_node/emacs/Terminal-emulator.html
Is it possible @arichiardi was not using term mode? Or why is emacs giving a TTY if it can't handle ANSI sequences?

We could theoretically support node's NODE_NO_READLINE flag by copy-pasting what node does internally. But I'm not sure that's the right solution for this particular issue.
https://nodejs.org/api/repl.html#repl_using_the_node_js_repl_with_advanced_line_editors

^[[1G^[[0J is the sequence to move the cursor to the beginning of the line and erase the entire line. (not super-helpful, but I googled it, so here you go)

[cspotcode]

NODE_NO_READLINE support has been added in v9.0.0: https://github.com/TypeStrong/ts-node/releases/tag/v9.0.0

I'm pretty sure this is the correct fix for this class of problem. If anyone finds that it does not work for them, please file an issue.