Re^2: BEGIN and END blocks, use strict and scoping

If I understand you correctly, the END block can make use of lexical variables defined in the file before the END block itself. This would obviate the need for using a BEGIN block to test for the presence/absence on disk of a given file. It would also mean that I could place use strict; in its customary position.

The following little script should illustrate the point in various ways depending on whether the file present is indeed present and depending on whether the croak call is live or commented-out.

#!/usr/local/bin/perl
use strict;
use warnings;
use File::Copy;
use Carp;
use Test::More (qw|no_plan|);

my $test = "/Users/jimk/present";
my $hide = $test . '.hidden';
my $status;

if (-f $test) {
    $status = 1;
    move($test, $hide);
    ok(! -f $test, "original file no longer present");
    ok(  -f $hide, "hidden file present");
} else {
    open FH, ">$test";
    print FH "1\n";
    close FH;
    ok(-f $test, "file created where it didn't previously exist");
    ok(1, "test not relevant");
}

my $trick = 0;
if (! $trick) {
    croak "Trick is false";
}

END {
    if ($status) {
        move($hide, $test);
        ok(! -f $hide, "hidden file no longer present");
        ok(  -f $test, "original file once again present");
    } else {
        unlink $test;
        ok(! -f $test, "specially created file has been removed");
        ok(1, "test not relevant");
    }
}
[download]

Update: While the solution above guarantees that the testing process is (more) non-destructive, it does have one drawback, AFACIT. When the croak occurs earlier in the file, (1) the total number of tests run is reduced by the quantity lying between the croak and the END block and (2) the numbers associated with the tests inside the END block are no longer at the end of the range predicted by the plan.

Revised example:


#!/usr/local/bin/perl
use strict;
use warnings;
use File::Copy;
use Carp;
use Test::More 
tests => 7;
# (qw|no_plan|);

my $test = "/Users/jimk/present";
my $hide = $test . '.hidden';
my $status;
my $trick = 0;

if (-f $test) {
    $status = 1;
    move($test, $hide);
    ok(! -f $test, "original file no longer present");
    ok(  -f $hide, "hidden file present");
} else {
    open FH, ">$test";
    print FH "1\n";
    close FH;
    ok(-f $test, "file created where it didn't previously exist");
    ok(1, "test not relevant");
}

croak "Trick is false" unless $trick;

ok('alpha', "alpha reached");
ok('beta', "beta reached");
ok('gamma', "gamma reached");

# croak "Trick is false" unless $trick;

END {
    if ($status) {
        move($hide, $test);
        ok(! -f $hide, "hidden file no longer present");
        ok(  -f $test, "original file once again present");
    } else {
        unlink $test;
        ok(! -f $test, "specially created file has been removed");
        ok(1, "test not relevant");
    }
}
[download]

... produces (assuming that present was indeed present at the outset):

1..7
ok 1 - original file no longer present
ok 2 - hidden file present
Trick is false at end.pl line 28
ok 3 - hidden file no longer present
ok 4 - original file once again present
# Looks like you planned 7 tests but only ran 4.
# Looks like your test died just after 4.
[download]

Tests 3 and 4 above are not the third and fourth as you would intuitively predict from eyeballing the file. You become more dependent on the croak message in locating the error within the file.

Thanks!

Jim Keenan

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