21 Jun
2023
21 Jun
'23
11:10 p.m.
Issue #19742 has been updated by ioquatix (Samuel Williams).
I'll add my observation that Marshal states it cannot handle anonymous modules, but I
say, it cannot handle ANY non-permanent (temporary) modules (assuming `permanent?` as
defined above). The difference is subtle but demonstrated by this example:
```ruby
# (1) Expected:
point = Struct.new(:x, :y)
Marshal.dump(point.new(1, 2)) # can't dump anonymous class
#<Class:0x00000001084f14c0> (TypeError)
# (2) Point2 is not anonymous (it did have a name), but it's also not permanent (the
name is no longer valid).
Point = Struct.new(:x, :y)
point = Point
Point2 = Point
Object.send(:remove_const, :Point)
Marshal.dump(Point2.new(1, 2)) # undefined class/module Point (ArgumentError)
# (3) Try to trick Marshal:
Point = Struct.new(:x, :y)
Marshal.dump(point.new(1, 2)) # Point can't be referred to (TypeError)
```
In all the above examples, the marshalled class may or may not be anonymous, but it's
always not permanent, according to my (slightly fixed) definition:
```ruby
class Module
def permanent?
Object.const_get(self.name).equal?(self) rescue nil
end
end
```
If being "not anonymous" was the only criteria, re-assigning the constants would
----------------------------------------
Feature #19742: Introduce `Module#anonymous?`
https://bugs.ruby-lang.org/issues/19742#change-103642
* Author: ioquatix (Samuel Williams)
* Status: Open
* Priority: Normal
----------------------------------------
As a follow-on <from https://bugs.ruby-lang.org/issues/19521>gt;, I'd like propose
we introduce `Module#anonymous?`.
In some situations, like logging/formatting, serialisation/deserialization, debugging or
meta-programming, we might like to know if a class is a proper constant or not.
However, this brings about some other issues which might need to be discussed.
After assigning a constant, then removing it, the internal state of Ruby still believes
that the class name is permanent, even thought it's no longer true.
e.g.
```
m = Module.new
m.anonymous? # true
M = m
m.anonyomous # false
Object.send(:remove_const, :M)
M # uninitialized constant M (NameError)
m.anonymous? # false
```
Because RCLASS data structure is not updated after the constant is removed, internally the
state still has a "permanent class name".
I want to use this proposal to discuss this issue and whether there is anything we should
do about such behaviour (or even if it's desirable).
Proposed PR: https://github.com/ruby/ruby/pull/7966
cc @fxn
--
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