Package: dpkg
Version: 1.19.0.5
Severity: minor
Hi,
There are some examples in Dpkg::Version that (if followed) would
imply that the problem will reject the version number "0" despite it
being valid.
Example:
"""
boolean evaluation
When the Dpkg::Version object is used in a boolean evaluation (for
example in "if ($v)" or "$v || 'default'") it returns its string representation
if the
version stored is valid ($v->is_valid()) and undef otherwise.
"""
This gives "surprising" results for version 0, which has a string
value that is considered false. To improve the correctness of the
examples. I have come to the following alternative examples:
-> "if (defined($v) and $v->is_valid())"
-> "$v // 'default'"
Sadly, the "if"-case is no longer elegant but that is the best I could
come up with that worked if $v is possibly undef and still have it
work. However, it no longer serves as a good example for "boolean
evaluation" (but neither did the original if you want to support the
version "0").
I have used the below to experiment/find the bug:
"""
use v5.20;
use Dpkg::Version;
my $v = Dpkg::Version->new("0");
my $v_or_fallback = $v || 'default';
my $v_dor_fallback = $v // 'default';
say "$v is valid" if $v->is_valid;
if ($v) {
say "$v is true";
} else {
say "$v is false";
}
say "\$v || 'default' = $v_or_fallback";
say "\$v // 'default' = $v_dor_fallback";
"""
Result:
"""
0 is valid
0 is false
$v || 'default' = default
$v // 'default' = 0
"""
Thanks,
~Niels
