Test::Warn, 'use' vs 'require'

asarih has asked for the wisdom of the Perl Monks concerning the following question:

I want to use Test::Warn in my tests. Since it has many dependencies, I might not have that module on every system that I want to run the tests. So I need to skip the tests that uses this module.

Normally, I would do:

use Test::More qw(no_plan);

SKIP: {
    eval { require Test::Warn };
    skip 'Test::Warn not found', 1 if $@;
    warning_like { warn "warning!" } qr(warning), 'basic warning';
}
[download]

But, on a system that does have Test::Warn, this will fail with this diagnostic message:

Can't call method "warning_like" without a package or object reference

If I use Test::Warn instead, the above test works (and of course, fails on systems that don't have Test::Warn).

I read documentation on use and require, but I cannot figure out how to get around this problem. (Since perl is not complaining about the exported symbol "warning_like", I assume that import has been successfully run by the time that line is executed.)

I'd appreciate any help.

Comment on Test::Warn, 'use' vs 'require' Download Code

Replies are listed 'Best First'.
Re: Test::Warn, 'use' vs 'require' by chromatic (Archbishop) on Sep 27, 2006 at 21:31 UTC
You need to load Test::Warn before `perl` compiles the `warning_like()` statements, because that function has a prototype. The easiest way may be to set a flag. `my $have_test_warn = 0; BEGIN { eval { require Test::Warn; Test::Warn->import(); $have_test_warn = 1; }; }` [download] Then test for `$have_test_warn` in your `SKIP` blocks.	[reply] [d/l] [select]
Re^2: Test::Warn, 'use' vs 'require' by Joost (Canon) on Sep 27, 2006 at 23:49 UTC
Ah right, I didn't spot the codeblock prototype. In other words, to make sure the code compiles without warnings if the mode isn't there, this should work: `warning_like( sub { warn "warning!" }, qr(warning), 'basic warning');` [download] "What should it profit a man, if he should win a flame war, yet lose his cool?"	[reply] [d/l]
Re^3: Test::Warn, 'use' vs 'require' (&) by tye (Sage) on Sep 28, 2006 at 01:49 UTC
Make that: `&warning_like( sub { warn "warning!" }, qr(warning), 'basic warning' +);` [download] (note the `&`) so it will work even if the prototype gets loaded soon enough. Update: Ah, yes, `&` prototypes don't have this problem like some other prototypes do. - tye	[reply] [d/l] [select]
Re^4: Test::Warn, 'use' vs 'require' (&) by adrianh (Chancellor) on Sep 28, 2006 at 18:19 UTC
Re: Test::Warn, 'use' vs 'require' by Joost (Canon) on Sep 27, 2006 at 19:58 UTC
use `eval { require Test::Warn; Test::Warn->import(@use_args); };` [download] See use update: in other words, require does NOT import anything. if you want to use "require" as a replacement for "use" you'll have to call import() by hand. "What should it profit a man, if he should win a flame war, yet lose his cool?"	[reply] [d/l]
Re^2: Test::Warn, 'use' vs 'require' by asarih (Hermit) on Sep 27, 2006 at 20:09 UTC
The `eval` block appears to fail even on a system that does have Test::Warn. The content of "$@" is: Undefined subroutine &Test::Warn::import called at t/01-test_errors.t line 13.	[reply]
Re^3: Test::Warn, 'use' vs 'require' by Joost (Canon) on Sep 27, 2006 at 20:17 UTC
The eval block appears to fail even on a system that does have Test::Warn. Erm.. that's wierd. Are you sure you're calling `Test::Warn->import();` instead of `Test::Warn::import()` ? "What should it profit a man, if he should win a flame war, yet lose his cool?"	[reply] [d/l] [select]
Re^4: Test::Warn, 'use' vs 'require' by asarih (Hermit) on Sep 27, 2006 at 20:27 UTC
Re^5: Test::Warn, 'use' vs 'require' by Joost (Canon) on Sep 27, 2006 at 20:44 UTC
Re: Test::Warn, 'use' vs 'require' by asarih (Hermit) on Sep 28, 2006 at 02:04 UTC
Thanks, chromatic and Joost! I ended up doing this: `my $have_test_warn; BEGIN { eval { require Test::Warn; Test::Warn->import(); $have_test_warn = 1; }; } SKIP: { skip 'Test::Warn not installed', 4 unless $have_test_warn; .... }` [download] I didn't assign the value to `$have_test_warn` in the declaration. If I did, it is executed before it gets to the SKIP block, and the value is 0 again.	[reply] [d/l]


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