Damn Data::UUID

The Data::UUID module has the annoying behavior that it will not fail if you provide an invalid namespace when creating a v3 UUID. It will generate a UUID, but depending on the circumstances it may generate a different UUID in subsequent calls. Consider the following example:

#!/usr/bin/perl

use strict;
use warnings;

use Data::UUID;
use UUID::Tiny;

sub v3_data_uuid {
    my $namespace = shift;
    my $name = shift;
    my $ug = shift;
    $ug = new Data::UUID unless defined $ug; 
    return lc($ug->create_from_name_str($namespace, $name));
}

sub v3_uuid_tiny {
    my $namespace = shift;
    my $name = shift;
    return UUID_to_string(create_UUID(UUID_V3, $namespace, $name));
}

# Generate a v3 UUID using Data::UUID
print "Data::UUID\n";
my $ug = new Data::UUID;
print '  1. ', lc($ug->create_from_name_str(UUID_NS_DNS, 'abc')), "\n";
print '  2. ', lc($ug->create_from_name_str(UUID_NS_DNS, 'abc')), "\n";
print '  3. ', v3_data_uuid(UUID_NS_DNS, 'abc'), "\n";
print '  4. ', v3_data_uuid(UUID_NS_DNS, 'abc'), "\n";
print '  5. ', v3_data_uuid(UUID_NS_DNS, 'abc', $ug), "\n";

# Generate a v3 UUID using UUID::Tiny
print "UUID::Tiny\n";
print '  1. ', UUID_to_string(create_UUID(UUID_V3, UUID_NS_DNS, 'abc')), "\n";
print '  2. ', UUID_to_string(create_UUID(UUID_V3, UUID_NS_DNS, 'abc')), "\n";
print '  3. ', v3_uuid_tiny(UUID_NS_DNS, 'abc'), "\n";
print '  4. ', v3_uuid_tiny(UUID_NS_DNS, 'abc'), "\n";

# Generate a v3 UUID using Data::UUID with an invalid namespace
print "Data::UUID - bad namespace\n";
my $namespace = 'namespace';
print '  1. ', lc($ug->create_from_name_str($namespace, 'abc')), "\n";
print '  2. ', lc($ug->create_from_name_str($namespace, 'abc')), "\n";
print '  3. ', v3_data_uuid($namespace, 'abc'), "\n";
print '  4. ', v3_data_uuid($namespace, 'abc'), "\n";
print '  5. ', v3_data_uuid($namespace, 'abc', $ug), "\n";

# Generate a v3 UUID using UUID::Tiny with an invalid namespace
print "UUID::Tiny - bad namespace\n";
print '  1. ', UUID_to_string(create_UUID(UUID_V3, $namespace, 'abc')), "\n";

This example also uses UUID::Tiny as a point of comparison. The output that I get when running this example is:

$ ./uuid.pl 
Data::UUID
  1. 1fc38bb9-aae5-3dba-9894-38925088c9c0
  2. 1fc38bb9-aae5-3dba-9894-38925088c9c0
  3. 1fc38bb9-aae5-3dba-9894-38925088c9c0
  4. 1fc38bb9-aae5-3dba-9894-38925088c9c0
  5. 1fc38bb9-aae5-3dba-9894-38925088c9c0
UUID::Tiny
  1. 5bd670ce-29c8-3369-a8a1-10ce44c7259e
  2. 5bd670ce-29c8-3369-a8a1-10ce44c7259e
  3. 5bd670ce-29c8-3369-a8a1-10ce44c7259e
  4. 5bd670ce-29c8-3369-a8a1-10ce44c7259e
Data::UUID - bad namespace
  1. 15da4c6e-29ae-3f6c-a7ed-ec36373d4e5d
  2. 15da4c6e-29ae-3f6c-a7ed-ec36373d4e5d
  3. 8fa130be-2517-3e29-a087-c7d75545a62c
  4. 8fa130be-2517-3e29-a087-c7d75545a62c
  5. 8fa130be-2517-3e29-a087-c7d75545a62c
UUID::Tiny - bad namespace
UUID::Tiny::string_to_uuid(): 'namespace' is no UUID string! at ./uuid.pl line 50

When a valid UUID is used for the namespace, Data::UUID consistently generates the same value. However, if I pass in a bad value such as the string literal namespace, then I get different values depending on how/where/when it is called. UUID::Tiny on the other hand dies with a nice error message telling me exactly what is wrong.