[ruby-core:78321] [Ruby trunk Feature#12979] Avoid exception for #dup on Integer (and similar cases)
From:
nobu@...
Date:
2016-11-25 07:48:46 UTC
List:
ruby-core #78321
Issue #12979 has been updated by Nobuyoshi Nakada.
I found that a rubygems test ,`TestGemSpecification#test_initialize_copy_broken` in test/rubygems/test_gem_specification.rb, depends on this exception.
And rubyspec fails as usual.
```diff
diff --git i/object.c w/object.c
index 05bef4d..7075e13 100644
--- i/object.c
+++ w/object.c
@@ -423,7 +423,7 @@ rb_obj_dup(VALUE obj)
VALUE dup;
if (rb_special_const_p(obj)) {
- rb_raise(rb_eTypeError, "can't dup %s", rb_obj_classname(obj));
+ return obj;
}
dup = rb_obj_alloc(rb_obj_class(obj));
init_copy(dup, obj);
diff --git i/test/ruby/test_object.rb w/test/ruby/test_object.rb
index 7b3defa..2f80bc6 100644
--- i/test/ruby/test_object.rb
+++ w/test/ruby/test_object.rb
@@ -19,9 +19,9 @@
end
def test_dup
- assert_raise(TypeError) { 1.dup }
- assert_raise(TypeError) { true.dup }
- assert_raise(TypeError) { nil.dup }
+ assert_equal 1, 1.dup
+ assert_equal true, true.dup
+ assert_equal nil, nil.dup
assert_raise(TypeError) do
Object.new.instance_eval { initialize_copy(1) }
diff --git i/test/rubygems/test_gem_specification.rb w/test/rubygems/test_gem_specification.rb
index 87f0f36..0d51d93 100644
--- i/test/rubygems/test_gem_specification.rb
+++ w/test/rubygems/test_gem_specification.rb
@@ -1260,7 +1260,8 @@
s.version = '1'
end
- spec.instance_variable_set :@licenses, :blah
+ def (broken_license = Object.new).dup; raise TypeError; end
+ spec.instance_variable_set :@licenses, broken_license
spec.loaded_from = '/path/to/file'
e = assert_raises Gem::FormatException do
```
----------------------------------------
Feature #12979: Avoid exception for #dup on Integer (and similar cases)
https://bugs.ruby-lang.org/issues/12979#change-61686
* Author: Martin D端rst
* Status: Open
* Priority: Normal
* Assignee: Nobuyoshi Nakada
----------------------------------------
This is a proposal resulting from a discussion in Bug #11929. Because this is proposing a different solution from #11929, it has a new number.
#11929 shows that people are confused that e.g. 3.dup throws an exception (but Integer#dup is actually implemented, so Integer.respond_to? :dup => true).
Integer#dup should fail silently, returning the receiver, in the same way as Integer#freeze fails silently. Citing from #11929 (comment by Mike Vastola): "If the object can't be duped/cloned because it's an immediate, dup/clone should return the object itself. (There shouldn't be any harm in doing so since nothing about the object can be changed in the first place.)". Citing some more:
> I literally can't imagine any scenario in which a dev, when, say, coding a class with the line:
>
> return val.dup.freeze
> .. really wants an Exception thrown when val happens to be de-facto un-dup-able. What they really want is:
>
> return val.dup.freeze rescue val
The proposal also has the advantage that it leads to a much more unified, streamlined protocol, avoiding needless exposition of internals. It would do exactly what dup (and clone) are described to do, namely (pretend to) return a shallow copy.
--
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