Resolving 'prototype mismatch' warning

[1nickt]

Learned monks,

I am working on a test script:

#!/usr/bin/perl
use strict; use warnings;
use Test::More;

my @compressors = qw/ Foo::Bar Compress::Snappy Compress::LZ4 /;
for my $compressor ( @compressors ) {
    note "   Testing with $compressor";
    if ( ! eval "use $compressor; 1;" ) {
        note "   Cannot load $compressor - skipping tests";
        next;
    }
    note "   Ready";
}

Output:

#    Testing with Foo::Bar
#    Cannot load Foo::Bar - skipping tests
#    Testing with Compress::Snappy
#    Ready
#    Testing with Compress::LZ4
Prototype mismatch: sub main::compress ($) vs ($;$) at /perl5/perlbrew
+/perls/perl-5.22.1/lib/5.22.1/Exporter.pm line 66.
 at (eval 8) line 1.
Prototype mismatch: sub main::decompress ($) vs ($;$) at /perl5/perlbr
+ew/perls/perl-5.22.1/lib/5.22.1/Exporter.pm line 66.
 at (eval 8) line 1.
Prototype mismatch: sub main::uncompress ($) vs ($;$) at /perl5/perlbr
+ew/perls/perl-5.22.1/lib/5.22.1/Exporter.pm line 66.
 at (eval 8) line 1.
#    Ready

I understand why the warning is printed (the two modules have identical APIs), and I know I could work around it by making separate test files, but that's not desirable. Also, it's just a warning and the subs work fine when the second module is loaded, but the warnings are undesirable.

I have searched but not found a way to clear the symbol table so the second time through the loop the subs can be imported without the warning. I can't use any non-core modules for the solution. Any help greatly appreciated!

[jdporter]

Bleh. Those modules are automatically importing names into main? Turn that crap off!

Update: It's worse than I thought. Both of those modules do EXPORT rather than EXPORT_OK. Ugh. Have you ever wanted to strangle a programmer with his own entrails?

Well, so... remember that Exporter::import imports the names into your current namespace, which is only main by default. So you could set up a separate namespace for each test. That would be one good way to avoid namespace pollution/collisions.

[Corion]

GotToBTru suggested in the CB to use the () feature of use to prevent ->import being called:

...
eval "use $modulename (); 1";
...

That way, the pollution should be somewhat prevented.

[1nickt]

Solved: Thanks jdporter and choroba and corion (for help in CB).

By declaring a package name I can avoid the namespace collision:

  if ( $compressor ) {
    my $namespace = 'My::' . $compressor;
    if ( ! eval "package $namespace; use $compressor; 1;" ) {
      die "Could not load $compressor - $@";
    } else {
      ...
    }
  }

And then I can access the imported subs through my namespace by forming the full sub name into a string and by turning off strict refs:

  } else {
    my $compress   = "My::$compressor\::compress";

    no strict 'refs';
    my $compressed = &$compress( $raw ); 
    use strict 'refs';
  }

[LanX]

You are free to disable this specific warning.

Personally I wouldn't trust any tests run with cluttered namespaces and potential side effects.

So why don't you just spawn a new clean Perl process for each tested module?