Avoid calling >= on unknown receivers in ls command

[dejmedus]

If Ls#dump_methods is called with an obj whose ancestors alter >=, the comparison (c >= Object/c >= Class) may raise an error. For example:

class Foo; class << self; undef >=; end; end
foo = Foo.new
ls foo

Foo >= Object # NoMethodError     

To prevent this, we could defensively flip the comparison so that <= is called on known receivers

[tompng]

To solve the problem, the change looks good. However, ls foo ls Foo doesn't work when some other methods are missing:

<
constants
class_variables
to_s
ancestors
public_instance_methods

Unlike Object instances that we need to consider BasicObject, I think we can assume Classes doesn't undef/change most of these methods: constants, class_variables, to_s, ancestors, public_instance_methods.
But for <, I guess it might be removed and need to change if klass < Object to if Object > klass in the situation you are assuming.

Can you share what kind of situation :<= is removed? Will :> be removed too?
Do you know an existing gem that creates a class without :<=?
The correct fix depends on the situation what you are assuming, and needs to be commented in test code.

[dejmedus]

👋 Yes, sorry, I should have added more details! The situation came up in Rubydex where an undefined method '>=' NoMethodError occurred on c >= Class due to a shadowed singleton_class returning an instance rather than the real class (better details in this issue). I believe the singleton_class is okay due to #1177 and is being fixed in Rubydex, but this raised the idea that flipping the comparison might prevent situations where a foreign object behaved oddly when compared

need to change if klass < Object to if Object > klass in the situation

I've updated my commit with this change:)

[tompng]

Thank you for providing the background 👍
I've confirmed the bug that described in Shopify/rubydex#685 with IRB 1.17.0

irb(main):001* module Rubydex
irb(main):002*   class SingletonClass
irb(main):003*     def ancestors; [self] end
irb(main):004*   end
irb(main):005*   class Namespace
irb(main):006*     def singleton_class
irb(main):007*       SingletonClass.new
irb(main):008*     end
irb(main):009*   end
irb(main):010> end
irb(main):011> 
irb(main):012> 
=> :singleton_class
irb(main):013> ns = Rubydex::Namespace.new
=> #<Rubydex::Namespace:0x000000016221e2c0>
irb(main):014> ls ns
/path/to/.rbenv/versions/4.0.0/lib/ruby/gems/4.0.0/gems/irb-1.17.0/lib/irb/command/ls.rb:74:in 'block in IRB::Command::Ls#dump_methods': undefined method '>=' for an instance of Rubydex::SingletonClass (NoMethodError)

        singleton_ancestors = (singleton_class&.ancestors || []).reject { |c| c >= Class }

So the error is caused by:

Rubydex::SingletonClass.new >= Class
(irb):13:in '<main>': undefined method '>=' for an instance of Rubydex::SingletonClass (NoMethodError)

However, flipping the operator doesn't solve the problem. It still raises error because the receiver was not a Class that doesn't have :>=, but was a normal Object.

Class <= Rubydex::SingletonClass.new
(irb):14:in 'Module#<=': compared with non class/module (TypeError)

[tompng]

Closing because the original issue was not about Class that removed :>=, and already fixed by #1177