NAME

VERSION

SYNOPSIS

    use Path::IsDev qw(is_dev);

    if( is_dev('/some/path') ) {
        ...
    } else {
        ...
    }

DESCRIPTION

This has many useful applications, notably ones that require behaviours for "installed" modules to be different to those that are still "in development"

FUNCTIONS

    export PATH_ISDEV_DEBUG=1

    if( is_dev( $path ) ) {

    }

    Path::IsDev::is_dev

    use Path::IsDev qw( is_dev );

UNDERSTANDING AND DEBUGGING THIS MODULE

This module operates on a very simplistic level, and its easy for false-positives to occur.

There are two types of Heuristics, Postive/Confirming Heuristics, and Negative/Disconfirming Heuristics.

Positive Heuristics and Negative Heuristics are based solely on the presence of specific marker files in a directory, or special marker directories.

For instance, the files "META.yml", "Makefile.PL", and "Build.PL" are all Positive Heuristic markers, because their presence often indicates a "root" of a development tree.

And for instance, the directories "t/", "xt/" and ".git/" are also Positive Heuristic markers, because these structures are common in "perl" development trees, and uncommon in install trees.

However, these markers sometimes go wrong, for instance, consider you have a "local::lib" or "perlbrew" install in $HOME

    $HOME/
    $HOME/lib/
    $HOME/perl5/perls/perl-5.19.3/lib/site_perl/

Etc.

Under normal circumstances, neither $HOME nor those 3 paths are considered "dev".

However, all it takes to cause a false positive, is for somebody to install a "t" or "xt" directory, or a marker file in one of the above directories for "path_isdev($dir)" to return true.

This may not be a problem, at least, until you use "Path::FindDev" which combines "Path::IsDev" with recursive up-level traversal.

    $HOME/
    $HOME/lib/
    $HOME/perl5/perls/perl-5.19.3/lib/site_perl/

    find_dev('$HOME/perl5/perls/perl-5.19.3/lib/site_perl/') # returns false, because it is not inside a dev directory

    mkdir $HOME/t

    find_dev('$HOME/perl5/perls/perl-5.19.3/lib/site_perl/') # returns $HOME, because $HOME/t exists.

And it is this kind of problem that usually catches people off guard.

    PATH_ISDEV_DEBUG=1 \
        perl -Ilib -MPath::FindDev=find_dev \
        -E "say find_dev(q{/home/kent/perl5/perlbrew/perls/perl-5.19.3/lib/site_perl})"

    ...
    [Path::IsDev=0] + ::Tool::Dzil => 0 : dist.ini does not exist
    [Path::IsDev=0] + ::Tool::MakeMaker => 0 : Makefile.PL does not exist
    [Path::IsDev=0] + ::Tool::ModuleBuild => 0 : Build.PL does not exist
    [Path::IsDev=0] + ::META => 0 : META.json does not exist
    [Path::IsDev=0] + ::META => 1 : META.yml exists
    [Path::IsDev=0] + ::META => 1 : /home/kent/perl5/META.yml is a file
    [Path::IsDev=0] + ::META matched path /home/kent/perl5
    /home/kent/perl5

Whoops!.

    [Path::IsDev=0] + ::META => 1 : META.yml exists
    [Path::IsDev=0] + ::META => 1 : /home/kent/perl5/META.yml is a file

No wonder!

    rm /home/kent/perl5/META.yml

    PATH_ISDEV_DEBUG=1 \
        perl -Ilib -MPath::FindDev=find_dev \
        -E "say find_dev(q{/home/kent/perl5/perlbrew/perls/perl-5.19.3/lib/site_perl})"

    ...
    [Path::IsDev=0] Matching /home/kent/perl5
    ...
    [Path::IsDev=0] + ::TestDir => 0 : xt does not exist
    [Path::IsDev=0] + ::TestDir => 1 : t exists
    [Path::IsDev=0] + ::TestDir => 1 : /home/kent/perl5/t is a dir
    [Path::IsDev=0] + ::TestDir matched path /home/kent/perl5
    /home/kent/perl5

Double whoops!

    [Path::IsDev=0] + ::TestDir => 1 : t exists
    [Path::IsDev=0] + ::TestDir => 1 : /home/kent/perl5/t is a dir

And you could keep doing that until you rule out all the bad heuristics in your tree.

Or, you could use a negative heuristic.

    touch /home/kent/perl5/.path_isdev_ignore

    PATH_ISDEV_DEBUG=1 \
        perl -Ilib -MPath::FindDev=find_dev \
        -E "say find_dev(q{/home/kent/perl5/perlbrew/perls/perl-5.19.3/lib/site_perl})"
    ...
    [Path::IsDev=0] Matching /home/kent/perl5
    [Path::IsDev=0] - ::IsDev::IgnoreFile => 1 : .path_isdev_ignore exists
    [Path::IsDev=0] - ::IsDev::IgnoreFile => 1 : /home/kent/perl5/.path_isdev_ignore is a file
    [Path::IsDev=0] - ::IsDev::IgnoreFile excludes path /home/kent/perl5
    [Path::IsDev=0] no match found
    ...
    [Path::IsDev=0] Matching /
    ...
    [Path::IsDev=0] no match found

Success!

    [Path::IsDev=0] - ::IsDev::IgnoreFile => 1 : .path_isdev_ignore exists
    [Path::IsDev=0] - ::IsDev::IgnoreFile => 1 : /home/kent/perl5/.path_isdev_ignore is a file

HEURISTICS

HEURISTIC SETS

ADVANCED USAGE

    use Path::IsDev is_dev => { set => 'Basic' };
    use Path::IsDev is_dev => { set => 'SomeOtherSet' , -as => 'is_dev_other' };

    export PATH_ISDEV_DEFAULT_SET="SomeOtherSet"

    ...
    use Path::IsDev qw( is_dev );
    is_dev('/some/path') # uses SomeOtherSet

    export PATH_ISDEV_DEFAULT_SET="SomeOtherSet"

    ...
    use Path::IsDev  is_dev => { set => 'Basic' };
    is_dev('/some/path') # uses Basic, regardless of ENV

SECURITY

And if they managed to achieve that, if they could poison the privileged users %ENV, they could trick the privileged user into executing arbitrary code.

Though granted, if you can do either of those 2 things, you're probably security vulnerable anyway, and granted, if you could do either of those 2 things you could do much more evil things by the following:

    export PERL5OPT="-MEvil::Module"

So with that in understanding, saying this modules default utility is "insecure" is mostly a bogus argument.

And to that effect, this module does nothing to "lock down" that mechanism, and this module encourages you to NOT force a set, unless you NEED to, and strongly suggests that forcing a set for the purpose of security will achieve no real improvement in security, while simultaneously reducing utility.

AUTHOR

COPYRIGHT AND LICENSE

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.