Do I need to do escaping in my regex check?

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

Good day my fellow esteemed Monks!

I come to you today with what I think is an easy one... I'm doing a validation check on input data, but I'm not getting expected results. Down deep in my software I've got the following sub, which compares a value against a list of enum type values. The important part for this discussion is the regex check:

sub enum {
    my ($attr, $value, $constraints) = @_;

    my $enum_values = $constraints->{enum};

    if (scalar @$enum_values) {
        if (! (grep /^$value$/, @$enum_values)) {
            my $enum_values_string = join ', ', @$enum_values;
            return "Attribute $attr is enum type but value '$value' is
+n't one of '$enum_values_string'";
        }
    }

    return 0;
}
[download]

Here's the test failure, which shows the actual value I'm trying to send in, along with the actual allowed values. You can see by eye that there's a match (the "isn't one of" is a joined string of the allowed values, separated by comma):

Attribute PoweredBy is enum type but value 'None (Private Label)' isn't one of 'None (Private Label), Text, Banner, Extra' at tests/Email/035_email_model_broadcast.t line 199.

Is this a failure due to the parens not being escaped? What's the best way to handle this? I'd rather not have to escape the input data, and I can't manually escape the allowed values in the sub above as the data is pulled from a database.

Thanks,

-stevieb

Comment on Do I need to do escaping in my regex check? Select or Download Code

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Re: Do I need to do escaping in my regex check? by choroba (Cardinal) on Mar 14, 2022 at 14:34 UTC
If you are checking one of the values is present, you don't need a regex at all. `if (! grep $_ eq $value, @$enum_values) {` [download] If you want to match regexes, you need to store regexes, not strings. Use quotemeta to escape the strings. `map{substr$_->[0],$_->[1]\|\|0,1}[\\|\|{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^ARGV,3]`	[reply] [d/l] [select]
Re: Do I need to do escaping in my regex check? by hv (Prior) on Mar 14, 2022 at 14:39 UTC
Yes, the parens are being treated as regexp metacharacters. You can escape it outside the pattern using `quotemeta($value)`, or within the pattern using `\Q...\E`: `if (! (grep /^\Q$value\E$/, @$enum_values)) {` However I'd normally rather do this as a hash lookup - faster, and it's already an equality check: `my %enum_values = map +($_ => 1), @{ $constraints->{enum} }; if (keys(%enum_values) && !$enum_values{$value}) { my $enum_values_string = join ', ', sort keys %enum_values; ...` [download] Another option is using the List::Util function 'none' (or 'any' for the inverse): `use List::Util qw{ none }; if (none { $_ eq $value } @$enum_values) { ...` [download]	[reply] [d/l] [select]
Re: Do I need to do escaping in my regex check? by LanX (Saint) on Mar 14, 2022 at 14:43 UTC
> `grep /^$value$/,` Seems like you want `grep /^\Q$value$/, ...` (see `quotemeta` ), but I agree with brother choroba that you are overcomplicating things. If you want a literal string to be anchored at start `^` and end `$` , using `eq` is the straightforward solution.ł If you want the literal value to match partially, using `grep /\Q$value/, ...` without both anchors makes sense.˛ If you want $value to contain some regex syntax, you have to escape the unintended metas individually° updates °) like `"None \$Private Label\$"` , please note the need for double escaping aka slasheritis ˛) added missing \Q ł) see also 99 Perl Problems ;-) Cheers Rolf _{(addicted to the Perl Programming Language :) Wikisyntax for the Monastery}	[reply] [d/l] [select]


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Do I need to do escaping in my regex check?

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