Provided by: libpath-isdev-perl_1.001003-3_all 
NAME
Path::IsDev - Determine if a given Path resembles a development source tree
VERSION
version 1.001003
SYNOPSIS
use Path::IsDev qw(is_dev);
if( is_dev('/some/path') ) {
...
} else {
...
}
DESCRIPTION
This module is more or less a bunch of heuristics for determining if a given path is a
development tree root of some kind.
This has many useful applications, notably ones that require behaviours for "installed"
modules to be different to those that are still "in development"
FUNCTIONS
debug
Debug callback.
To enable debugging:
export PATH_ISDEV_DEBUG=1
"is_dev"
Using an "import"'ed "is_dev":
if( is_dev( $path ) ) {
}
Though the actual heuristics used will be based on how "import" was called.
Additionally, you can call
Path::IsDev::is_dev
without "import"ing anything, and it will behave exactly the same as if you'd imported it
using
use Path::IsDev qw( is_dev );
That is, no "set" specification is applicable, so you'll only get the "default".
UNDERSTANDING AND DEBUGGING THIS MODULE
Understanding how this module works, is critical to understand where you can use it, and
the consequences of using it.
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
Negative Heuristics bundled with this distribution
Just remember, a Negative Heuristic excludes the path it is associated with
• "IsDev::IgnoreFile" - ".path_isdev_ignore"
Positive Heuristics bundled with this distribution
• "Changelog" - Files matching "Changes", "Changelog", and similar, case insensitive,
extensions optional.
• "DevDirMarker" - explicit ".devdir" file to indicate a project root.
• "META" - "META.yml"/"META.json"
• "MYMETA" - "MYMETA.yml"/"MYMETA.json"
• "Makefile" - Any "Makefile" format documented supported by GNU Make
• "TestDir" - A directory called either "t/" or "xt/"
• "Tool::DZil" - A "dist.ini" file
• "Tool::MakeMaker" - A "Makefile.PL" file
• "Tool::ModuleBuild" - A "Build.PL" file
• "VCS::Git" - A ".git" directory
HEURISTIC SETS
Heuristic Sets Bundled with this distribution
• "Basic" - The basic heuristic set that contains most, if not all heuristics.
ADVANCED USAGE
Custom Sets
"Path::IsDev" has a system of "sets" of Heuristics, in order to allow for pluggable and
flexible heuristic types.
Though, for the vast majority of cases, this is not required.
use Path::IsDev is_dev => { set => 'Basic' };
use Path::IsDev is_dev => { set => 'SomeOtherSet' , -as => 'is_dev_other' };
Overriding the default set
If for whatever reason the "Basic" set is insufficient, or if it false positives on your
system for some reason, the "default" set can be overridden.
export PATH_ISDEV_DEFAULT_SET="SomeOtherSet"
...
use Path::IsDev qw( is_dev );
is_dev('/some/path') # uses SomeOtherSet
Though this will only take priority in the event the set is not specified during "import"
If this poses a security concern for the user, then this security hole can be eliminated
by declaring the set you want in code:
export PATH_ISDEV_DEFAULT_SET="SomeOtherSet"
...
use Path::IsDev is_dev => { set => 'Basic' };
is_dev('/some/path') # uses Basic, regardless of ENV
SECURITY
Its conceivable, than an evil user could construct an evil set, containing arbitrary and
vulnerable code, and possibly stash that evil set in a poorly secured privileged users
@INC
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
Kent Fredric <kentnl@cpan.org>
COPYRIGHT AND LICENSE
This software is copyright (c) 2017 by Kent Fredric <kentfredric@gmail.com>.
This is free software; you can redistribute it and/or modify it under the same terms as
the Perl 5 programming language system itself.