So far as I can tell this code erroneously reports a scalar $moo:
{ package X; our @moo; }
use Devel::Symdump;
use Data::Dumper;
print Devel::Symdump->new("X")->scalars; # prints "X::moo"
Googling, I gather this isn't strictly a bug in this module, but more a
"feature" of Perl, for example see this thread:
http://stackoverflow.com/questions/3391572/perl-iterate-over-a-typeglob
Specifically, from perlref (perl 5.14.2):
*foo{THING} returns undef if that particular THING hasn't been used yet,
except in the case of scalars. *foo{SCALAR} returns a reference to an
anonymous scalar if $foo hasn't been used yet. This might change in a
future release.
So in the above example in general it is impossible to tell if $moo was
declared or not, unless it has been assigned a defined value.
Even though nothing much can be done about this, I think it would be
useful to specifically point it out in the documentation, and save
uninformed users some head-scratching. A suggested amendment is
attached, but anything equivalent would do.
References to similar modules with different approaches might also help
(e.g. Package::Stash which attempts to go a step further than this one
and check if a scalar entry is defined, which may be useful in some cases).
| Subject: | Symdump.pm.diff |
--- Symdump.pm~ 2007-06-25 07:07:38.000000000 +0100
+++ Symdump.pm 2012-05-10 00:08:44.683643430 +0100
@@ -371,6 +371,13 @@
symbols. Unknown symbols are usually either formats or variables that
haven't yet got a defined value.
+Note that scalar symbol table entries are a special case. If a symbol
+table entry exists at all, presence of a scalar is currently
+unknowable, due to a feature of Perl described in perlref "Making
+References" point 7. For example, this package will mark a scalar
+value C<$foo> as present if any of C<@foo>, C<%foo>, C<&foo> etc. have
+been declared or used.
+
=item as_string
=item as_HTML