in reply to announce missing modules

You can put code refs in @INC, which means you could do this automatically, rather than having to wrap your list of modules...

package MissingModules;
my %missing = ();
BEGIN {
    push( @INC, sub {
        my ( $code, $mod ) = @_;
        $mod =~ s#/#::#g;
        $mod =~ s/\.pm$//;
        $missing{ $mod }++;
        open( my $fh, '+>', undef );
        print {$fh} "package $mod;\n1;\n";
        seek( $fh, 0, 0 );
        return $fh;
    } );
}
INIT {
    if ( my @list = keys %missing ) {
        warn "Please install CPAN modules: cpan -i @list\n";
        exit;
    }
}

1;

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Then in your other code:

#!/usr/bin/perl 
use MissingModules;
use CGI;
use Foo;
use Bar;
use Baz;

1;

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When you run it, you will get...

% perl test.pl
Please install CPAN modules: cpan -i Bar Baz Foo

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We're not surrounded, we're in a target-rich environment!

Replies are listed 'Best First'.
Re^2: announce missing modules
by Arif (Acolyte) on Feb 24, 2008 at 17:40 UTC
    That's a great idea. I started to play with something similar and got the following for the anon function on the @INC array. 
    BEGIN {
        use 5.8.0;
        use vars qw(@missing);

        push @INC, sub { 
                my ($coderef, $filename) = @_;

                # Ignore non-modules.
                return undef unless ($filename =~ s/.pm$//);

                # Remember the module.
                $filename =~ s/\//::/g;
                push @missing, $filename;

                # Return a dummy file handle.
                open my $FH, '<', \'1;';
                $FH;
        };
}

    [download]
    The INIT block is a great idea. 
    INIT {
        # Check and clean up.
        die "Missing modules.\n\tcpan -i ", join(' ',' @missing), "\n\
+n" if (@missing);
        pop @INC;
}

    [download]
    The open my $FH, '<', \'1;'; is available in perl 5.8.8.

    Is there a better way to deduce the module name than removing the .pm extension and replacing /s with ::? Will it work on non-UNIX platforms?

    Popping the function off again seems like a good idea.

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[select]
      Just for the record, I found the flaw in this scheme. One of my included modules includes 'Storable', which tries to include 'Log::Agent'. If it fails then the 'Storable' module does something else. The above @INC scheme forces the user to install the conditional module. This shouldn't happen.

      So back to the old method (slightly refined to handle module versions and import lists) 

      
{
   our @missing =
         map +(m/^(\S+)/),
         grep !eval "use $_; 1",
         grep $_,
         split /\s*\n\s*/, "
              Storable
              File::Basename
              A::B wq(a b c)
              Foo::Bar
              CGI qw/:standard/
        " and die "Please install CPAN modules: cpan -i @missing\n";
}

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