Don't enable test mode by TERM=dumb

[tompng]

Problem

In IRB's test code, TERM=dumb triggers Reline's test mode io Reline::GeneralIO (unlike the name, this is not a general io)

In practice, TERM=dumb seems to be used in real world. (example: pry/pry#2303)
It will unintentionally enables Reline's test mode and cause problems.

I think Reline should not use TERM=dumb to enable test mode. We need another way to enable it, or remove this test mode after fixing IRB's test not to depend on this.

[st0012]

I haven't looked much into the issue yet, but we need to be very cautious about this change because many projects, like Rails and debug, use TERM=dumb to turn on the Reline test mode. If we did decide to implement this change, let's make sure we roll it out gradually (e.g. supporting both TERM=dumb and the alternative for a while) so we have time to help those projects updating their tests.

[dgutov]

FWIW, if we're talking about Reline inside Emacs, then removing special handling for TERM=dumb is not enough: if I just change those checks, that brings back the ▽ problem.

[tompng]

If we're doing this, we also need to disable ▽ and "\e[6n" (Query Cursor Position) if TERM=dumb.

[eregon]

like Rails and debug, use TERM=dumb to turn on the Reline test mode.

I'm surprised by this, does anyone using Rails or the debug gem really want the Reline test mode?
It outputs a lot of extra output which seems unusable except maybe when debugging Reline itself:

$ echo 'my input' > in
$ TERM=dumb ruby -rreadline -e 'p Readline; p [STDIN,STDOUT,STDERR].map(&:tty?); p Readline.readline("> ", true)' < in |& ruby -e 'p STDIN.read' 
"Reline\n[false, false, false]\n> > mmymy my imy inmy inpmy inpumy input> my input\r\n\"my input\"\n"

(context: #886)

[st0012]

It's used in those projects to run integration tests that can verify the console's outupt. Not by their users.

[eregon]

Would you have an example?
I find it unlikely that some test would check e.g. that my input results in mmymy my imy inmy inpmy inpumy input or so.

I'd expect tests would use TERM=dumb to avoid extra escape sequences from Reline (#886), but then (non-reline-internal) tests would also expect no extra prints like mmymy my imy inmy inpmy inpumy input.

[eregon]

Reline test mode

What does that do?
I think it's most people expectation that TERM=dumb means no extra escape sequences, and also that it behaves like a dumb terminal so e.g. echo'es the input as-is or with minimal changes, and without what looks like reline debugging output or so.

IOW, I doubt that disabling the mmymy my imy inmy inpmy inpumy input debugging would break any non-reline-internal test.
And that the original issue seems worth solving and seems not so likely to break anything.

[st0012]

https://github.com/rails/rails/blob/7ff005d9416388f0fa6d89895c4c560c13717164/railties/test/engine/commands_test.rb#L40

The goal is to just capture input for testing. But unfortunately we have to print every character too.