Bug #8743
closedInconsistent behaviour calling public_methods on class (Plus documentation slightly ambiguous)
Description
=begin
= Background
I was trying to identify classes on which a specific class method (def self.xx) was actually defined (in the case of multiple levels of inheritance). This currently doesn't seem to be possible, although the docs suggest that calling class.public_methods(false) should do this.
While investigating, I discovered that the behaviour of calling instance.public_methods(false) is not consistent with that of calling class.public_methods(false) [They should be different, of course, but the behaviour should be consistent]. The attached test script highlights this.
= Steps to Reproduce
Run the attached ruby script
= Expected Result
Ideally, all tests pass, but at least test_consistent_behaviour
should pass
= Actual Results
test_this_is_what_i_expect, and test_consistent_behaviour both fail.
= Example test output
steves@sapphire ~/s/t/ruby> env RUBYLIB=./lib ./ruby ~/foo.rb
Run options:
Running tests:¶
[2/5] PublicMethodsTest#test_consistent_behaviour = 0.00 s
- Failure:
PublicMethodsTest#test_consistent_behaviour [/Users/steves/foo.rb:73]:
Differences: bar. "bar" is inherited from A, but doesn't include methods inherited from Object!
[5/5] PublicMethodsTest#test_this_is_what_i_expect = 0.00 s
2) Failure:
PublicMethodsTest#test_this_is_what_i_expect [/Users/steves/foo.rb:59]:
Differences: allocate, new, superclass.
Finished tests in 0.005998s, 833.6112 tests/s, 2834.2781 assertions/s.
5 tests, 17 assertions, 2 failures, 0 errors, 0 skips
ruby -v: ruby 2.1.0dev (2013-08-06 trunk 42401) [x86_64-darwin12.4.0]
Seen on ruby 1.8, 2.0 and trunk
=end
Files
Updated by jeremyevans0 (Jeremy Evans) about 5 years ago
- Status changed from Open to Closed
- Backport deleted (
1.9.3: UNKNOWN, 2.0.0: UNKNOWN)
The reason for this interesting behavior is because the documentation for include flag (2nd argument) for public_methods
is not precise. It states:
If the all parameter is set to false, only those methods
in the receiver will be listed.
However, the behavior is actually:
If the all parameter is set to false, the list will include methods
in ancestors, stopping after a non-singleton class is encountered
(including the methods from the non-singleton class).
The lookup process for Empty.public_methods(false)
is something like this:
- Empty.singleton_class # adds no methods
- Object.singleton_class # adds no methods
- BasicObject.singleton_class # adds no methods
- Class # adds 3 methods
[:allocate, :superclass, :new]
- Module # does not get here, as Class is not a singleton class
So that is the reason Empty.public_methods(false)
gives you [:allocate, :superclass, :new]
.
B.public_methods(false)
including singleton methods from A
is similar:
- B.singleton_class # adds no methods
- A.singleton_class # adds 1 method
[:bar]
- Object.singleton_class # adds no methods
- BasicObject.singleton_class # adds no methods
- Class # adds 3 methods
[:allocate, :superclass, :new]
- Module # does not get here, as Class is not a singleton class
Which is the reason that Bar.public_methods(false)
gives you [:bar, :allocate, :superclass, :new]
.
I'm not sure it worth updating the documentation to be more precise in this area, but I'm open to suggestions.