This cop identifies places where Hash#merge! can be replaced by Hash#[]=.

Example:

hash.merge!(a: 1)
hash.merge!({'key' => 'value'})
hash.merge!(a: 1, b: 2)

This cop enforces the consistent usage of %-literal delimiters.

Specify the 'default' key to set all preferred delimiters at once. You can continue to specify individual preferred delimiters to override the default.

Example:

# Style/PercentLiteralDelimiters:
#   PreferredDelimiters:
#     default: '[]'
#     '%i':    '()'

# good
%w[alpha beta] + %i(gamma delta)

# bad
%W(alpha #{beta})

# bad
%I(alpha beta)

This cop checks for chaining of a block after another block that spans multiple lines.

Example:

Thread.list.find_all do |t|
  t.alive?
end.map do |t|
  t.object_id
end

Use a guard clause instead of wrapping the code inside a conditional expression

Example:

# bad
def test
  if something
    work
  end
end

# good
def test
  return unless something
  work
end

# also good
def test
  work if something
end

# bad
if something
  raise 'exception'
else
  ok
end

# good
raise 'exception' if something
ok

This cop checks for the use of output safety calls like htmlsafe, raw, and safeconcat. These methods do not escape content. They simply return a SafeBuffer containing the content as is. Instead, use safe_join to join content and escape it and concat to concatenate content and escape it, ensuring its safety.

Example:

user_content = "hi"

# bad
"
#{user_content}
".html_safe
=> ActiveSupport::SafeBuffer
"
hi
"

# good
content_tag(:p, user_content)
=> ActiveSupport::SafeBuffer
"
<b>hi</b>
"

# bad
out = ""
out << "
#{user_content}
"
out << "
#{user_content}
"
out.html_safe
=> ActiveSupport::SafeBuffer
"
hi
hi
"

# good
out = []
out << content_tag(:li, user_content)
out << content_tag(:li, user_content)
safe_join(out)
=> ActiveSupport::SafeBuffer
"
<b>hi</b>
<b>hi</b>
"

# bad
out = "
trusted content
".html_safe
out.safe_concat(user_content)
=> ActiveSupport::SafeBuffer
"
trusted_content
hi"

# good
out = "
trusted content
".html_safe
out.concat(user_content)
=> ActiveSupport::SafeBuffer
"
trusted_content
<b>hi</b>"

# safe, though maybe not good style
out = "trusted content"
result = out.concat(user_content)
=> String "trusted contenthi"
# because when rendered in ERB the String will be escaped:
<%= result %>
=> trusted content<b>hi</b>

# bad
(user_content + " " + content_tag(:span, user_content)).html_safe
=> ActiveSupport::SafeBuffer
"hi <span><b>hi</b></span>"

# good
safe_join([user_content, " ", content_tag(:span, user_content)])
=> ActiveSupport::SafeBuffer
"<b>hi</b> <span>&lt;b&gt;hi&lt;/b&gt;</span>"

This cop checks for redundant uses of self.

self is only needed when:

• Sending a message to same object with zero arguments in presence of a method name clash with an argument or a local variable.

  Note, with using explicit self you can only send messages with public or protected scope, you cannot send private messages this way.

  Example:

  def bar :baz end

  def foo(bar) self.bar # resolves name clash with argument end

  def foo2 bar = 1 self.bar # resolves name clash with local variable end

• Calling an attribute writer to prevent an local variable assignment

  attr_writer :bar

  def foo self.bar= 1 # Make sure above attr writer is called end

Special cases:

We allow uses of self with operators because it would be awkward otherwise.

This cop checks for usage of comparison operators (==, >, <) to test numbers as zero, positive, or negative. These can be replaced by their respective predicate methods. The cop can also be configured to do the reverse.

The cop disregards nonzero? as it its value is truthy or falsey, but not true and false, and thus not always interchangeable with != 0.

Example:

# EnforcedStyle: predicate (default)

# bad

foo == 0
0 > foo
bar.baz > 0

# good

foo.zero?
foo.negative?
bar.baz.positive?

Example:

# EnforcedStyle: comparison

# bad

foo.zero?
foo.negative?
bar.baz.positive?

# good

foo == 0
0 > foo
bar.baz > 0

This cop checks dynamic find_by_* methods. Use find_by instead of dynamic method. See. https://github.com/bbatsov/rails-style-guide#find_by

Example:

# bad
User.find_by_name(name)

# bad
User.find_by_name_and_email(name)

# bad
User.find_by_email!(name)

# good
User.find_by(name: name)

# good
User.find_by(name: name, email: email)

# good
User.find_by!(email: email)