`and` / `or` keywords with `raise` / `fail`

[smanolloff]

The idea of banning the and & or keywords is really cool.

However, there is one specific case in which they may be preferred:

authenticate_user! || fail AuthenticationFailure, 'Invalid credentials'
# SyntaxError: unexpected '\n', expecting :: or '[' or '.'

authenticate_user! or fail AuthenticationFailure, 'Invalid credentials'
# (this works ok)

Of course, we we could just use

fail AuthenticationFailure, 'Invalid credentials' unless authenticate_user!

... but doesn't it degrade readability?

Is the usage of and or or, immediately followed by a raise or fail, justified?
I would be happy if you could share your thoughts!

[philoserf]

I find the object.test or fail 'message' construction is very common in the wild.

[bbatsov]

I find the object.test or fail 'message' construction is very common in the wild.

In Perl. :-) Seriously, though - yeah, it's popular to some extent but way more people use modifier if/unless for such code.

[smanolloff]

Sure, i guess that is fine.
But we should not forget that the if / unless one-liners are not exactly the same as the boolean operators:

def current_user
  fail 'Authentication failed' unless @current_user ||= authenticate
  @current_user # need to return explicitly
end

def current_user
  @current_user ||= authenticate or fail 'Authentication failed'
end

[luizdamim]

👍 for allowing and/or followed by raise/fail. I use it quite frequently in my codebase.

[Ajedi32]

I think the real crux of the issue is that and and or are perfectly fine to use for their intended purpose: as control flow operators. The problems they cause usually occur when people try to use them in place of || and && as boolean operators.

Then again though, if and unless can usually be used in place of or and and, so idk...

[bbatsov]

I think the real crux of the issue is that and and or are perfectly fine to use for their intended purpose: as control flow operators.

Pretty sure those were never intended as flow of control operators. This is something which people came up with to justify their existence. It's pretty clear they were actually added to facilitate a style of programming with less parentheses in it, which is a good or a bad thing, depending who you ask.

[cheerfulstoic]

Avdi Grimm has a really great (and free) RubyTapas episode about this:

http://devblog.avdi.org/2014/08/26/how-to-use-rubys-english-andor-operators-without-going-nuts/

👍 on use as flow control operators!

[pirj]

Duplicate of #730