NAME
    Path::Class::Rule - File finder using Path::Class

VERSION
    version 0.011

SYNOPSIS
      use Path::Class::Rule;

      my $rule = Path::Class::Rule->new; # match anything
      $rule->file->size(">10k");         # add/chain rules

      # iterator interface
      my $next = $rule->iter( @dirs );
      while ( my $file = $next->() ) {
        ...
      }

      # list interface
      for my $file ( $rule->all( @dirs ) ) {
        ...
      }

DESCRIPTION
    This module iterates over files and directories to identify ones
    matching a user-defined set of rules. The API is based heavily on
    File::Find::Rule, but with more explicit distinction between matching
    rules and options that influence how directories are searched. A
    "Path::Class::Rule" object is a collection of rules (match criteria)
    with methods to add additional criteria. Options that control directory
    traversal are given as arguments to the method that generates an
    iterator.

    Here is a summary of features for comparison to other file finding
    modules:

    *   provides many "helper" methods for specifying rules

    *   offers (lazy) iterator and flattened list interfaces

    *   returns Path::Class objects

    *   custom rules implemented with callbacks

    *   breadth-first (default) or pre- or post-order depth-first searching

    *   follows symlinks (by default, but can be disabled)

    *   directories visited only once (no infinite loops)

    *   doesn't chdir during operation

    *   provides an API for extensions

USAGE
  Constructors
   "new"
      my $rule = Path::Class::Rule->new;

    Creates a new rule object that matches any file or directory. It takes
    no arguments. For convenience, it may also be called on an object, in
    which case it still returns a new object hat matches any file or
    directory.

   "clone"
      my $common      = Path::Class::Rule->new->file->not_empty;
      my $big_files   = $common->clone->size(">1MB");
      my $small_files = $common->clone->size("<10K");

    Creates a copy of a rule object. Useful for customizing different rule
    objects against a common base.

  Matching and iteration
   "iter"
      my $next = $rule->iter( @dirs, \%options);
      while ( my $file = $next->() ) {
        ...
      }

    Creates a subroutine reference iterator that returns a single
    Path::Class object when dereferenced. This iterator is "lazy" -- results
    are not pre-computed.

    It takes as arguments a list of directories to search and an optional
    hash reference of control options. If no search directories are
    provided, the current directory is used ("."). Valid options include:

    *   "depthfirst" -- Controls order of results. Valid values are "1"
        (post-order, depth-first search), "0" (breadth-first search) or "-1"
        (pre-order, depth-first search). Default is 0.

    *   "error_handler" -- Catches errors during execution of rule tests.
        Default handler dies with the filename and error.

    *   "follow_symlinks" -- Follow directory symlinks when true. Default is
        1.

    *   "loop_safe" -- Prevents visiting the same directory more than once
        when true. Default is 1.

    Filesystem loops might exist from either hard or soft links. The
    "loop_safe" option prevents infinite loops, but adds some overhead by
    making "stat" calls. Because directories are visited only once when
    "loop_safe" is true, matches could come from a symlinked directory
    before the real directory depending on the search order. To get only the
    real files, turn off "follow_symlinks". Turning "loop_safe" off and
    leaving "follow_symlinks" on avoids "stat" calls and will be fastest,
    but with the risk of an infinite loop and repeated files. The default is
    slow, but safe.

    The "error_handler" parameter must be a subroutine reference. It will be
    called when a rule test throws an exception. The first argument will be
    the Path::Class object being inspected and the second argument will be
    the exception.

    The Path::Class objects inspected and returned will be relative to the
    search directories provided. If these are absolute, then the objects
    returned will have absolute paths. If these are relative, then the
    objects returned will have relative paths.

   "all"
      my @matches = $rule->all( @dir, \%options );

    Returns a list of Path::Class objects that match the rule. It takes the
    same arguments and has the same behaviors as the "iter" method. The
    "all" method uses "iter" internally to fetch all results.

   "test"
      if ( $rule->test( $path ) ) { ... }

    Test a file path against a rule. Used internally, but provided should
    someone want to create their own, custom iteration algorithm.

  Logic operations
    "Path::Class::Rule" provides three logic operations for adding rules to
    the object. Rules may be either a subroutine reference with specific
    semantics (described below in "EXTENDING") or another
    "Path::Class::Rule" object.

   "and"
      $rule->and( sub { -r -w -x $_ } ); # stacked filetest example
      $rule->and( @more_rules );

    Adds one or more constraints to the current rule. E.g. "old rule AND
    new1 AND new2 AND ...". Returns the object to allow method chaining.

   "or"
      $rule->or(
        $rule->new->name("foo*"),
        $rule->new->name("bar*"),
        sub { -r -w -x $_ },
      );

    Takes one or more alternatives and adds them as a constraint to the
    current rule. E.g. "old rule AND ( new1 OR new2 OR ... )". Returns the
    object to allow method chaining.

   "not"
      $rule->not( sub { -r -w -x $_ } );

    Takes one or more alternatives and adds them as a negative constraint to
    the current rule. E.g. "old rule AND NOT ( new1 AND new2 AND ...)".
    Returns the object to allow method chaining.

   "skip"
      $rule->skip(
        $rule->new->dir->not_writeable,
        $rule->new->dir->name("foo"),
      );

    Takes one or more alternatives and will prune a directory if any of the
    criteria match. For files, it is equivalent to
    "$rule->not($rule->or(@rules))". Returns the object to allow method
    chaining.

    This method should be called as early as possible in the rule chain. See
    "skip_dirs" below for further explanation and an example.

RULE METHODS
    Rule methods are helpers that add constraints. Internally, they generate
    a closure to accomplish the desired logic and add it to the rule object
    with the "and" method. Rule methods return the object to allow for
    method chaining.

  File name rules
   "name"
      $rule->name( "foo.txt" );
      $rule->name( qr/foo/, "bar.*");

    The "name" method takes one or more patterns and creates a rule that is
    true if any of the patterns match the basename of the file or directory
    path. Patterns may be regular expressions or glob expressions (or
    literal names).

   "iname"
      $rule->iname( "foo.txt" );
      $rule->iname( qr/foo/, "bar.*");

    The "iname" method is just like the "name" method, but matches
    case-insensitively.

   "skip_dirs"
      $rule->skip_dirs( @patterns );

    The "skip_dirs" method skips directories that match one or more
    patterns. Patterns may be regular expressions or globs (just like
    "name"). Directories that match will not be returned from the iterator
    and will be excluded from further search.

    Note: this rule should be specified early so that it has a chance to
    operate before a logical shortcut. E.g.

      $rule->skip_dirs(".git")->file; # OK
      $rule->file->skip_dirs(".git"); # Won't work

    In the latter case, when a ".git" directory is seen, the "file" rule
    shortcuts the rule before the "skip_dirs" rule has a chance to act.

  File test rules
    Most of the "-X" style filetest are available as boolean rules. The
    table below maps the filetest to its corresponding method name.

       Test | Method               Test |  Method
      ------|-------------        ------|----------------
        -r  |  readable             -R  |  r_readable
        -w  |  writeable            -W  |  r_writeable
        -w  |  writable             -W  |  r_writable
        -x  |  executable           -X  |  r_executable
        -o  |  owned                -O  |  r_owned
            |                           |
        -e  |  exists               -f  |  file
        -z  |  empty                -d  |  directory, dir
        -s  |  nonempty             -l  |  symlink
            |                       -p  |  fifo
        -u  |  setuid               -S  |  socket
        -g  |  setgid               -b  |  block
        -k  |  sticky               -c  |  character
            |                       -t  |  tty
        -T  |  ascii
        -B  |  binary

    For example:

      $rule->file->nonempty; # -f -s $file

    The -X operators for timestamps take a single argument in a form that
    Number::Compare can interpret.

       Test | Method
      ------|-------------
        -A  |  accessed
        -M  |  modified
        -C  |  changed

    For example:

      $rule->modified(">1"); # -M $file > 1

  Stat test rules
    All of the "stat" elements have a method that takes a single argument in
    a form understood by Number::Compare.

      stat()  |  Method
     --------------------
           0  |  dev
           1  |  ino
           2  |  mode
           3  |  nlink
           4  |  uid
           5  |  gid
           6  |  rdev
           7  |  size
           8  |  atime
           9  |  mtime
          10  |  ctime
          11  |  blksize
          12  |  blocks

    For example:

      $rule->size(">10K")

  Depth rules
      $rule->min_depth(3);
      $rule->max_depth(5);

    The "min_depth" and "max_depth" rule methods take a single argument and
    limit the paths returned to a minimum or maximum depth (respectively)
    from the starting search directory.

  Perl file rules
      # All perl rules
      $rule->perl_files;

      # Individual perl file rules
      $rule->perl_module;     # .pm files
      $rule->perl_pod;        # .pod files 
      $rule->perl_test;       # .t files
      $rule->perl_installer;  # Makefile.PL or Build.PL
      $rule->perl_script;     # .pl or 'perl' in the shebang

    These rule methods match file names (or a shebang line) that are typical
    of Perl distribution files.

  Version control file rules
      # Skip all known VCS files
      $rule->skip_vcs;

      # Skip individual VCS files
      $rule->skip_cvs;
      $rule->skip_rcs;
      $rule->skip_svn;
      $rule->skip_git;
      $rule->skip_bzr;
      $rule->skip_hg;

    Skips files and/or prunes directories related to a version control
    system. Just like "skip_dirs", these rules should be specified early to
    get the correct behavior.

  Other rules
   "dangling"
      $rule->symlink->dangling;
      $rule->not_dangling;

    The "dangling" rule method matches dangling symlinks. Use it or its
    inverse to control how dangling symlinks should be treated. Note that a
    dangling symlink will be returned by the iterator as a Path::Class::File
    object.

   "shebang"
      $rule->shebang(qr/#!.*\bperl\b/);

    The "shebang" rule takes a list of regular expressions or glob patterns
    and checks them against the first line of a file.

  Negated rules
    Most rule methods have a negated form preceded by "not_".

      $rule->not_name("foo.*")

    Because this happens automatically, it includes somewhat silly ones like
    "not_nonempty" (which is thus a less efficient way of saying "empty").

    Rules that skip directories or version control files do not have a
    negated version.

EXTENDING
  Custom rule subroutines
    Rules are implemented as (usually anonymous) subroutines callbacks that
    return a value indicating whether or not the rule matches. These
    callbacks are called with two arguments. The first argument is a
    Path::Class object, which is also locally aliased as the $_ global
    variable for convenience in simple tests.

      $rule->and( sub { -r -w -x $_ } ); # tests $_

    The second argument is a hash reference that can be used to maintain
    state. Keys beginning with an underscore are reserved for
    "Path::Class::Rule" to provide additional data about the search in
    progress. For example, the "_depth" key is used to support minimum and
    maximum depth checks.

    The custom rule subroutine must return one of three values:

    *   A true value -- indicates the constraint is satisfied

    *   A false value -- indicates the constraint is not satisfied

    *   "0 but true" -- a special return value that signals that a directory
        should not be searched recursively

    The "0 but true" value will shortcut logic (it is treated as "true" for
    an "or" rule and "false" for an "and" rule). For a directory, it ensures
    that the directory will not be returned from the iterator and that its
    children will not be evaluated either. It has no effect on files -- it
    is equivalent to returning a false value.

    For example, this is equivalent to the "max_depth" rule method with a
    depth of 3:

      $rule->and(
        sub {
          my ($path, $stash) = @_;
          return $stash->{_depth} <= 3 ? 1 : "0 but true";
        }
      );

    Files of depth 4 will not be returned by the iterator; directories of
    depth 4 will not be returned and will not be searched.

    Generally, if you want to do directory pruning, you are encouraged to
    use the "skip" method instead of writing your own logic using "0 but
    true".

  Extension modules and custom rule methods
    One of the strengths of File::Find::Rule is the many CPAN modules that
    extend it. "Path::Class::Rule" provides the "add_helper" method to
    provide a similar mechanism for extensions.

    The "add_helper" class method takes three arguments, a "name" for the
    rule method, a closure-generating callback, and a flag for not
    generating a negated form of the rule. Unless the flag is true, an
    inverted "not_*" method is generated automatically. Extension classes
    should call this as a class method to install new rule methods. For
    example, this adds a "foo" method that checks if the filename is "foo":

      package Path::Class::Rule::Foo;

      use Path::Class::Rule;

      Path::Class::Rule->add_helper(
        foo => sub {
          my @args = @_; # do this to customize closure with arguments
          return sub {
            my ($item) = shift;
            return if $item->is_dir;
            return $item->basename =~ /^foo$/;
          }
        }
      );

      1;

    This allows the following rule methods:

      $rule->foo;
      $fule->not_foo;

    The "add_helper" method will warn and ignore a helper with the same name
    as an existing method.

LEXICAL WARNINGS
    If you run with lexical warnings enabled, "Path::Class::Rule" will issue
    warnings in certain circumstances (such as a read-only directory that
    must be skipped). To disable these categories, put the following
    statement at the correct scope:

      no warnings 'Path::Class::Rule';

CAVEATS
    This is an early release for community feedback and contribution. Some
    features are still unimplemented:

    *   Untainting options

    *   Some File::Find::Rule helpers (e.g. "grep")

    *   Extension class loading via "import()"

    Filetest operators and stat rules are subject to the usual portability
    considerations. See perlport for details.

SEE ALSO
    There are many other file finding modules out there. They all have
    various features/deficiencies, depending on your preferences and needs.
    Here is an (incomplete) list of alternatives, with some comparison
    commentary.

    File::Find is part of the Perl core. It requires the user to write a
    callback function to process each node of the search. Callbacks must use
    global variables to determine the current node. It only supports
    depth-first search (both pre- and post-order). It supports pre- and
    post-processing callbacks; the former is required for sorting files to
    process in a directory. File::Find::Closures can be used to help create
    a callback for File::Find.

    File::Find::Rule is an object-oriented wrapper around File::Find. It
    provides a number of helper functions and there are many more
    "File::Find::Rule::*" modules on CPAN with additional helpers. It
    provides an iterator interface, but precomputes all the results.

    File::Next provides iterators for file, directories or "everything". It
    takes two callbacks, one to match files and one to decide which
    directories to descend. It does not allow control over breadth/depth
    order, though it does provide means to sort files for processing within
    a directory. Like File::Find, it requires callbacks to use global
    variables.

    Path::Class::Iterator walks a directory structure with an iterator. It
    is implemented as Path::Class subclasses, which adds a degree of extra
    complexity. It takes a single callback to define "interesting" paths to
    return. The callback gets a Path::Class::Iterator::File or
    Path::Class::Iterator::Dir object for evaluation.

    File::Find::Object and companion File::Find::Object::Rule are like
    File::Find and File::Find::Rule, but without File::Find inside. They use
    an iterator that does not precompute results. They can return
    File::Find::Object::Result objects, which give a subset of the utility
    of Path::Class objects. File::Find::Object::Rule appears to be a literal
    translation of File::Find::Rule, including oddities like making "-M"
    into a boolean.

    File::chdir::WalkDir recursively descends a tree, calling a callback on
    each file. No iterator. Supports exclusion patterns. Depth-first
    post-order by default, but offers pre-order option. Does not process
    symlinks.

    File::Find::Iterator is based on iterator patterns in Higher Order Perl.
    It allows a filtering callback. Symlinks are followed automatically
    without infinite loop protection. No control over order. It offers a
    "state file" option for resuming interrupted work.

    File::Find::Declare has declarative helper rules, no iterator, is
    Moose-based and offers no control over ordering or following symlinks.

    File::Find::Node has no iterator, does matching via callback and offers
    no control over ordering.

    File::Set builds up a set of files to operate on from a list of
    directories to include or exclude, with control over recursion. A
    callback is applied to each file (or directory) in the set. There is no
    iterator. There is no control over ordering. Symlinks are not followed.
    It has several extra features for checksumming the set and creating
    tarballs with /bin/tar.

SUPPORT
  Bugs / Feature Requests
    Please report any bugs or feature requests through the issue tracker at
    <http://rt.cpan.org/Public/Dist/Display.html?Name=Path-Class-Rule>. You
    will be notified automatically of any progress on your issue.

  Source Code
    This is open source software. The code repository is available for
    public review and contribution under the terms of the license.

    <https://github.com/dagolden/path-class-rule>

      git clone https://github.com/dagolden/path-class-rule.git

AUTHOR
    David Golden <dagolden@cpan.org>

COPYRIGHT AND LICENSE
    This software is Copyright (c) 2011 by David Golden.

    This is free software, licensed under:

      The Apache License, Version 2.0, January 2004

