Survey breaks when stdin is piped (eg unix pipe)

[noerw]

Currently survey does not support reading from piped stdin.
The issue lies in several layers:

• with piped stdin, Cursor.Location() (called by all prompts implicitly) fails with io.EOF:
  

  survey/terminal/cursor.go

  Lines 106 to 109 in f45c05b

  	text, err := reader.ReadSlice(byte('R'))
  	if err != nil {
  	return nil, err
  	}

  
  Subsequently, no input is read, and control commands printed instead of being applied.

• RuneReader does not treat io.EOF as end of input, but aborts and returns it as error, which is unnecessary (e.g. MultiLine input waiting for 3 newlines until it continues)

I'm not exactly sure how a piped stdin differs from a terminal stdin, so I don't know how to fix this.
One step surely would be to change Cursor, so that it detects piped stdin, and switches to a NO-OP mode?

[cben]

When input is a pipe, survey library is probably not best experience. Do you have a use for the prompts and escape sequences on stdout?
Consider detecting it with https://github.com/mattn/go-isatty and just reading from stdin without prompts.

Or are you using a pipe for testing your program that uses survey?
(I'm playing with that now, with mixed success; I should probably stick to the advice at https://github.com/AlecAivazis/survey#testing
about go-expect, vt10x, and tests inside this repo 😁)

Currently, reading from a pipe you are also likely to hit #282 — terminal state is not cleaned up.

[noerw]

When input is a pipe, survey library is probably not best experience. Do you have a use for the prompts and escape sequences on stdout?

Piping stdin & stdout are two separate things, with different use cases: Our program can benefit from being the last element in a pipeline, while primarily used interactively. The prompts also look nice, no matter if they are interactive.

Consider detecting it with https://github.com/mattn/go-isatty and just reading from stdin without prompts.

That's what we currently do, until this is resolved. But there is no reason for Multiline to error on EOF.

[saurabhaditya]

I was trying to use a CLI with heredoc that errored and landed here debugging that. The library used is this 'survey' that does not take bash style heredoc for inputs.