Endless Method Keyword/Operator Precedence Check

[phene]

Is your feature request related to a problem?

Consider the following code

def foo = true and false
def bar = true && false

foo # => true
bar # => false

Because the = operator has higher precedence than and or or, they will not be included as part the method.

Describe the solution you'd like

A rubocop check to detect operators/keywords with lower precedence than = on the same line as an endless expression would be incredibly helpful in avoiding this sort of footgun.

[vlad-pisanov]

Such a cop is badly needed. Our team has run into if/unless gotchas several times:

def foo = 42 if cond
# NoMethodError: undefined method `cond' for main

[dvandersluis]

@vlad-pisanov I'm looking into this one. There is a somewhat common pattern of defining methods unless defined, such as:

def foo
  42
end unless defined?(:foo)

which could be written in endless form potentially:

def foo = 42 unless defined?(:foo)

How would you handle that? Exception in the cop specifically for defined??

[vlad-pisanov]

@dvandersluis I haven't encountered this pattern before. Maybe it could be conditionally permitted for endless methods with a cop option like AllowInlineModifiers or something? 🤔

[dvandersluis]

Perhaps I'm misremembering its prevalance. A github code search reveals some uses but not as prevalent as I thought. There's also unless respond_to? in any case.

I think I'll just leave it for now and if issues come up we can address.

[phene]

FWIW, def foo = 42 unless defined?(:foo) and

def foo
  42
end unless defined?(:foo)

seem like major anti-patterns.

[dvandersluis]

Agreed it's an anti-pattern, just wanted to avoid unexpected behaviour.