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Avoid calling >= on unknown receivers in ls command #1193

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4 changes: 2 additions & 2 deletions lib/irb/command/ls.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -72,8 +72,8 @@ def dump_methods(o, klass, obj)
singleton_class = begin Kernel.instance_method(:singleton_class).bind(obj).call; rescue TypeError; nil end
dumped_mods = Array.new
ancestors = klass.ancestors
ancestors = ancestors.reject { |c| c >= Object } if klass < Object
singleton_ancestors = (singleton_class&.ancestors || []).reject { |c| c >= Class }
ancestors = ancestors.reject { |c| Object <= c } if Object > klass
singleton_ancestors = (singleton_class&.ancestors || []).reject { |c| Class <= c }
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@tompng tompng Mar 28, 2026

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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.

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@dejmedus dejmedus Mar 29, 2026

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👋 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:)

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@tompng tompng Mar 29, 2026

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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)


# singleton_class' ancestors should be at the front
maps = class_method_map(singleton_ancestors, dumped_mods) + class_method_map(ancestors, dumped_mods)
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10 changes: 10 additions & 0 deletions test/irb/test_command.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -757,6 +757,16 @@ def test_ls_with_no_singleton_class
assert_match(/Numeric#methods:\s+/, out)
assert_match(/Integer#methods:\s+/, out)
end

def test_ls_with_object_altering_comparison_methods
out, err = execute_lines(
"class BadCompare; class << self; undef >=; undef <; end; def foo; end; end\n",
"obj = BadCompare.new\n",
"ls obj\n",
)
assert_empty err
assert_match(/BadCompare#methods:\s+foo/, out)
end
end

class ShowDocTest < CommandTestCase
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