Examples of `ActiveSupport::Deprecation`

deprecation.rb

require 'active_support'

class Foo
  def foo
    "foo"
  end

  def bar
    ActiveSupport::Deprecation.warn("bar is deprecated")

    foo
  end

  def bar1
    ActiveSupport::Deprecation.warn("bar1 is deprecated", caller)

    foo
  end

  def bar2
    ActiveSupport::Deprecation.deprecation_warning("bar2 is deprecated")

    foo
  end

  def bar3
    ActiveSupport::Deprecation.deprecation_warning("bar3 is deprecated", :bar)

    foo
  end

  def bar4
    ActiveSupport::Deprecation.deprecation_warning("bar4 is deprecated", "use bar instead")

    foo
  end

  def bar5
    ActiveSupport::Deprecation.deprecation_warning("bar5 is deprecated", "use bar instead", caller)

    foo
  end

  def bar5
    ActiveSupport::Deprecation.deprecation_warning("bar5 is deprecated", "use bar instead", caller)

    foo
  end

  def bar6
    deprecator = ActiveSupport::Deprecation.new("1.0", "foo")

    deprecator.deprecation_warning("bar6 is deprecated")

    foo
  end
end

Foo1 = ActiveSupport::Deprecation::DeprecatedConstantProxy.new('Foo1', 'Foo')

class Bar
  def initialize
    deprecator = ActiveSupport::Deprecation.new("1.0", "foo")
    @request = ActiveSupport::Deprecation::DeprecatedInstanceVariableProxy.new(self, :request, :@request, deprecator)
    @_request = :my_request
  end

  def request
    @_request
  end

  def old_request
    @request
  end
end

@old_object = ActiveSupport::Deprecation::DeprecatedObjectProxy.new(Object.new, "Don't use this object anymore!")

module Fred
  extend self

  def foo; end
  def bar; end
  def baz; end
end

ActiveSupport::Deprecation.deprecate_methods(Fred, :foo, bar: :qux, baz: 'use Bar#baz instead')

class Baz
  class Deprecator
    def deprecation_warning(deprecated_method_name, message, callstack = nil)
      message = "#{deprecated_method_name} is deprecated and will be removed from MyLibrary | #{message}"
      Kernel.warn message
    end
  end

  def self.deprecator
    Deprecator.new
  end

  def foo
    true
  end

  def bar
    true
  end
  deprecate foo: :bar, deprecator: deprecator
end

class MyCustomHandler
  def self.call(message, callstack)
    true
  end
end

ActiveSupport::Deprecation.behavior = :stderr
# ActiveSupport::Deprecation.behavior = [:stderr, :log]
# ActiveSupport::Deprecation.behavior = MyCustomHandler
# ActiveSupport::Deprecation.behavior = proc { |message, callstack|
#   # custom stuff
# }
#
# https://github.com/rails/rails/commit/3f04785f77899b286d02a0a95dd7fbfc341dc999
# https://github.com/rails/rails/commit/e4637530cd181fb03b35ce5fa2e95508f4bc1e1c

The examples for deprecation_warning have more than just a method name as the first argument, e.g. deprecation_warning("bar2 is deprecated"). However, I believe it should just be the method name: deprecation_warning("bar2") as the "is deprecated" is added by the default behavior.