Bug #18998
closedKernel#Integer does not convert SimpleDelegator object expectly
Description
Kernel#Integer method doens not convert a SimpleDelegator object of which value is a String.
This is an sample code.
require 'delegate'
p Integer(SimpleDelegator.new('0x10'))
I expect Kernel#Integer to convert the input value as a String and the expected returned value is 16
.
Hoever the actual returned value is 0
so it's seemed that #to_i
method is just called.
taichi@LAPTOP-TVTKLNFD:temp
$ cat test.rb
require 'delegate'
p Integer(SimpleDelegator.new('0x10'))
taichi@LAPTOP-TVTKLNFD:temp
$ ruby test.rb
0
Which is the correct behavior?
Updated by taichi730 (Taichi Ishitani) about 2 years ago
- Subject changed from Kernel#Integer does not convert SimpleDelegator expectly to Kernel#Integer does not convert SimpleDelegator object expectly
Updated by byroot (Jean Boussier) about 2 years ago
So this behavior isn't documented, so it's hard to say wether it's correct:
Integer(arg, base=0, exception: true) → integer or nil
Converts arg to an Integer. Numeric types are converted directly (with floating point numbers being truncated). base (0, or between 2 and 36) is a base for integer string representation. If arg is a String, when base is omitted or equals zero, radix indicators (0, 0b, and 0x) are honored. In any case, strings should consist only of one or more digits, except for that a sign, one underscore between two digits, and leading/trailing spaces are optional. This behavior is different from that of String#to_i. Non string values will be converted by first trying to_int, then to_i.
Passing nil raises a TypeError, while passing a String that does not conform with numeric representation raises an ArgumentError. This behavior can be altered by passing exception: false, in this case a not convertible value will return nil.
However the intent of the implementation is fairly clear:
static VALUE
rb_convert_to_integer(VALUE val, int base, int raise_exception)
{
VALUE tmp;
// snip
if (RB_FLOAT_TYPE_P(val)) {
double f = RFLOAT_VALUE(val);
if (!raise_exception && !isfinite(f)) return Qnil;
if (FIXABLE(f)) return LONG2FIX((long)f);
return rb_dbl2big(f);
}
else if (RB_INTEGER_TYPE_P(val)) {
return val;
}
else if (RB_TYPE_P(val, T_STRING)) {
return rb_str_convert_to_inum(val, base, TRUE, raise_exception);
}
else if (NIL_P(val)) {
if (!raise_exception) return Qnil;
rb_raise(rb_eTypeError, "can't convert nil into Integer");
}
tmp = rb_protect(rb_check_to_int, val, NULL);
if (RB_INTEGER_TYPE_P(tmp)) return tmp;
rb_set_errinfo(Qnil);
if (!raise_exception) {
VALUE result = rb_protect(rb_check_to_i, val, NULL);
rb_set_errinfo(Qnil);
return result;
}
return rb_to_integer(val, "to_i", idTo_i);
}
If passed an object that is neither a direct string nor a native numeric, Integer
first tries to invoke to_int
, then fallback to invoke to_i
.
I suppose a case could be made to first try to call to_str
.
Updated by taichi730 (Taichi Ishitani) about 2 years ago
Thank you for your reply.
I understood that there is no documented specification and the current implementation.
How should Integer method behave for this case?
My thought is that Integer method should convert a Delegator object like when a String is given.
Because of this, I override Integer method like below in my project.
module Kernel
alias_method :__orignal_Integer, :Integer
def Integer(arg, base = 0, exception: true)
arg = arg.__getobj__ if arg.is_a?(::Delegator)
__orignal_Integer(arg, base, exception: exception)
end
end
Updated by byroot (Jean Boussier) about 2 years ago
My thought is that Integer method should convert a Delegator object like when a String is given.
I don't think it would be advisable for Kernel#Integer
to know about Delegator
. Delegator
is just a class from the stdlib, you could implement the same yourself and that wouldn't solve your problem.
I think based on the spec lined up above, it would be best if you defined #to_int
on your delegator. But I don't know your full use case, so not sure if it's relevant.
Either way I don't think there is really a bug here, aside from maybe the method needed more documentation.
A change of behavior would fall under a feature request, and a proper spec would need to be drafted. The only possible change I could see would be to try to call to_str
between to_int
and to_i
, but that could be a breaking change, so a hard sell.
Updated by taichi730 (Taichi Ishitani) about 2 years ago
it would be best if you defined #to_int on your delegator
I've tried this approach but it was failed because base
and exception
arguments cannot be passed to #to_i
method on my delegator.
Therefore, I've overridden Kernel#Integer
method.
Updated by nobu (Nobuyoshi Nakada) about 2 years ago
- Status changed from Open to Closed
Applied in changeset git|7563604fb868d87057733f52d780d841fc1ab6bb.
[Bug #18998] Honor #to_str
next to #to_int
in Kernel#Integer
Updated by nobu (Nobuyoshi Nakada) about 2 years ago
- Backport changed from 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN to 2.7: REQUIRED, 3.0: REQUIRED, 3.1: REQUIRED