Branch: refs/heads/yves/fix_universal_import_fragility
Home: https://github.com/Perl/perl5
Commit: 5ca0b4b539d7ce9ed9977a03d85e5fac33809f9e
https://github.com/Perl/perl5/commit/5ca0b4b539d7ce9ed9977a03d85e5fac33809f9e
Author: Yves Orton <demer...@gmail.com>
Date: 2023-07-18 (Tue, 18 Jul 2023)
Changed paths:
M gv.c
M lib/UNIVERSAL.pm
M pod/perldiag.pod
M t/op/universal.t
M universal.c
Log Message:
-----------
Fix assorted bugs related to not having a UNIVERSAL::import
Since perl 5.0 the methods "import" and "unimport" have been
special cased in gv.c (unimport was removed for a while) to
not produce errors if they are called. This is partly
because
use Foo;
is defined to be
BEGIN {
require Foo;
Foo->import();
}
which would blow up if there is no import function defined in
Foo, for instance if it were defining a class and not a package
which exports modules.
This special case can be broken by simple code like
\&UNIVERSAL::isa
which will create a stub function which then blows up when it is
used. Notably the module "autouse" which is shipped with perl will
trigger this behavior.
A related issue is that if you ask for a function to be exported
from a module that does not have support for exporting there is no
error, eg:
use File::Spec qw(catfile);
will silently succeed without exporting a catfile function. This is
exacerbated on case insensitive file systems when the module name
is case-mismatched, the use succeeds but the export does not, leading
to confusion, eg:
use LIst::Util qw(sum); # note the typo!
will load List::Util but will not export the sum function.
This patch defines UNIVERSAL::import() and UNIVERSAL::unimport()
functions. This prevents the "reference to \&UNIVERSAL::import" bug.
The function is defined to be a no-op unless arguments are passed into
the functions, in which case a warning is thrown indicating
that there is likely a problem. The error is modelled after the
error produced by calling a non-existent method or function:
./perl -Ilib -le'BEGIN{ my $import_sub= \&UNIVERSAL::import;}
use File::Spec qw(catfile);'
Attempt to call UNIVERSAL::import() with arguments via package File::Spec
(Perhaps you forgot to load "File::Spec"?) at -e line 1.
BEGIN failed--compilation aborted at -e line 1.
This fixes Issue #19416, Issue #19417, Issue #19418. See also Issue #19410 for
discussion, however this patch does not fix that case (it may not be
fixable.)
