Strings consisting '\t' or '\v' not interpreted in YAML

[Lord-KA]

When using escaped tab in string, YAML stops interpreting all escaped chars.

• OS: Linux
• OS Version: Ubuntu 22
• Architecture: x86_64

master

Steps to reproduce

Tarantool 2.10.0-beta1-1165-g0b622ac1a
type 'help' for interactive help
tarantool> a = '\t\n\n'
---
...

tarantool> a
---
- "\t\n\n"
...

tarantool> b = '\v\n\n'
---
...

tarantool> b
---
- "\v\n\n"
...

tarantool> c = '\\\n\n'
---
...

tarantool> c
---
- |+
  \

...

Actual behavior

Strings printed in YAML consisting '\t and \v' are not interpreted.

Expected behavior

Strings printed in YAML consisting '\t' and '\v' are interpreted.

[Totktonada]

I guess (after a brief reading) that the specification allows both variants. But the goal of JSON and YAML are to be easy to interpret by a human. A human hardly distiguish a sequence of whitespaces from a tab. I think that current behavior (escape a tab) is the best choice.

[Lord-KA]

The problem is that we use YAML as default output in console. By definition it should be easy to read as an interface, but here if a module (in my case it was tarantool.compat.dump()) tries to output a complex string for a human to read, like help or some pretty dump, when it uses '\t' to e.g. align something user sees exactly escaped '\t'. I had to use multiple spaces instead and it doesn't seem like a good alternative.

[Totktonada]

I agree that #3012 would be pretty useful for a prose text (help messages and so on). However I disagree that tab escaping is a problem.

The only known use case is a formatted text within a string, like formatted help message. A tab may be rendered differently (different terminal emulators, text editors, documentation/emails/messaging apps, where the text will be pasted and so on) and it is better to always use whitespaces for formatting.

[Lord-KA]

I am not aware of any terminal emulator that interprets '\t' any other way, than several whitespaces. In case of several whitespaces, I think it would be preferable to leave the exact number of those to the renderer.

[Totktonada]

Several, but how many?

$ echo -e 'foo\tbar\nfoofoof\tbar'
foo	bar
foofoof	bar

This output looks differently in urxvt and in Vim. It also looks differently on GitHub with and without refined-github. There is no one way to show tabs.

$ echo -e 'foo\tbar\nfoofoofo\tbar'
foo	bar
foofoofo	bar

This output doesn't form columns in urxvt, but it is unclear, whether it'll do in other terminals.