formatting multiline boolean expressions

How should one format multiline boolean expressions? For instance maybe each condition is a long statement and it would be too long or unreadable on a single line. Or should this be avoided altogether? If so, what's the alternative?

I couldn't find any guidance on this in the style guide. Should it be added, whatever the verdict is?

One option:

def my_predicate?
  first_long_condition ||
  second_long_condition ||
  third_long_condition ||
  last_long_condition
end

Or maybe with indentation after the first one?

def my_predicate?
  first_long_condition ||
    second_long_condition ||
    third_long_condition ||
    last_long_condition
end

Or wrap only when you hit the line limit? With or without indenting?

def my_predicate?
  first_long_condition || second_long_condition ||
    third_long_condition || last_long_condition
end

Of course you could give each condition its own predicate method, but in many cases that's overkill:

def predicate_one?
  first_long_condition
end

# and so forth ...

def my_predicate?
  predicate_one? || predicate_two? || predicate_three? || predicate_four?
end

You could evaluate them separately and assign the results, but you forfeit short-circuit evaluation:

def my_predicate?
  a = first_long_condition
  b = second_long_condition
  c = third_long_condition
  d = last_long_condition

  a || b || c || d
end

This is related to #476 but not exactly the same.

Review the existing style guide and related issue #476, then resolve the formatting alternatives raised in this discussion. Done means the community-approved guidance for multiline boolean expressions is added to the style guide with examples.