How do I conditionally make warnings fatal?

Question

I want to have fatal errors that can be demoted to warnings (or conversely, warnings that can be promoted to fatal errors) depending on the user's preference. At present, I'm using `die` and overriding it like this: ``` my $force; BEGIN { no warnings 'once'; Getopt::Long::Configure('pass_through'); GetOptions('force', \$force); *CORE::GLOBAL::die = sub { warn @_ } if $force; Getopt::Long::Configure('no_pass_through'); } use My::Module; ... die "maybe"; ... exit(1) if $force; exit(0); # success! ``` I don't like this approach, mostly because there are a few places where I still want to die (e.g. missing command-line arguments). I'd rather change (most) instances of `die` to `warn` and do a conditional `use warnings FATAL => 'all'`1. The problem is that `use warnings` is lexically scoped, so this is ineffective: ``` if (!$force) { use warnings FATAL => 'all'; } ``` Attempting to use a postfix conditional is a syntax error: ``` use warnings FATAL => 'all' unless $force; ``` and `use` can…

Accepted Answer

You could try:

```
use if !$force, warnings => qw( FATAL all );
```

Yes, there's a module called `if` that is distributed with Perl to make it really easy to do conditional imports.

Note that this is evaluated at compile time, so `$force` needs to be defined at compile time. (Probably within a `BEGIN { ... }` block.) Based on the code samples in your question, you seem to have figured that part out already though.

Alternatively, more manual:

```
BEGIN {
    require warnings;
    warnings->import(qw/ FATAL all /) unless $force;
}
```

A completely different approach would be to use a signal handler `$SIG{__WARN__}` or `$SIG{__DIE__}` to decide to die or not at run-time.

How do I conditionally make warnings fatal?

Solution

Problem