Fix m2m regression from 8a67d9cf (simple but deadly)

[dbsrgits/DBIx-Class.git] / lib / DBIx / Class / _Util.pm

package # hide from PAUSE
  DBIx::Class::_Util;

use DBIx::Class::StartupCheck;  # load es early as we can, usually a noop

use warnings;
use strict;

use constant SPURIOUS_VERSION_CHECK_WARNINGS => ( "$]" < 5.010 ? 1 : 0);

my $mro_recursor_stack;

BEGIN {
  package # hide from pause
    DBIx::Class::_ENV_;

  use Config;

  use constant {

    # but of course
    BROKEN_FORK => ($^O eq 'MSWin32') ? 1 : 0,

    BROKEN_GOTO => ( "$]" < 5.008003 ) ? 1 : 0,

    HAS_ITHREADS => $Config{useithreads} ? 1 : 0,

    UNSTABLE_DOLLARAT => ( "$]" < 5.013002 ) ? 1 : 0,

    ( map
      #
      # the "DBIC_" prefix below is crucial - this is what makes CI pick up
      # all envvars without further adjusting its scripts
      # DO NOT CHANGE to the more logical { $_ => !!( $ENV{"DBIC_$_"} ) }
      #
      { substr($_, 5) => !!( $ENV{$_} ) }
      qw(
        DBIC_SHUFFLE_UNORDERED_RESULTSETS
        DBIC_ASSERT_NO_INTERNAL_WANTARRAY
        DBIC_ASSERT_NO_INTERNAL_INDIRECT_CALLS
        DBIC_STRESSTEST_UTF8_UPGRADE_GENERATED_COLLAPSER_SOURCE
        DBIC_STRESSTEST_COLUMN_INFO_UNAWARE_STORAGE
      )
    ),

    IV_SIZE => $Config{ivsize},

    OS_NAME => $^O,
  };

  if ( "$]" < 5.009_005) {
    require MRO::Compat;
    constant->import( OLD_MRO => 1 );

    #
    # Yes, I know this is a rather PHP-ish name, but please first read
    # https://metacpan.org/source/BOBTFISH/MRO-Compat-0.12/lib/MRO/Compat.pm#L363-368
    #
    # Even if we are using Class::C3::XS it still won't work, as doing
    #   defined( *{ "SubClass::"->{$_} }{CODE} )
    # will set pkg_gen to the same value for SubClass and *ALL PARENTS*
    #
    *DBIx::Class::_Util::get_real_pkg_gen = sub ($) {
      require Digest::MD5;
      require Math::BigInt;

      # the non-assign-unless-there-is-a-hash is deliberate
      ( $mro_recursor_stack->{cache} || {} )->{$_[0]}{gen} ||= (
        Math::BigInt->new( '0x' . ( Digest::MD5::md5_hex( join "\0", map {

          ( $mro_recursor_stack->{cache} || {} )->{$_}{methlist} ||= do {

            my $class = $_;

            no strict 'refs';
            my %methlist =
              map
                # this is essentially a uniq_by step
                # it is crucial on OLD_MRO
                {( Scalar::Util::refaddr($_) => $_ )}
                map
                  {
                    (
                      ref(\ "${class}::"->{$_} ) ne 'GLOB'
                        or
                      defined( *{ "${class}::"->{$_} }{CODE} )
                    )
                    ? ( \&{"${class}::$_"} )
                    : ()
                  }
                  keys %{ "${class}::" }
            ;

            # RV to be hashed up and turned into a number
            join "\0", (
              $class,
              map {(
                $_, # refaddr is sufficient, ignore names entirely
                @{
                  ( $mro_recursor_stack->{cache} || {} )->{attrs}{$_}
                    ||=
                  [ attributes::get( $methlist{$_} ) ]
                },
              )} sort keys %methlist
            ),
          }
        } ( 'UNIVERSAL', @{
          ( $mro_recursor_stack->{cache} || {} )->{$_[0]}{linear_isa}
            ||=
           mro::get_linear_isa($_[0])
        } ) ) ) )
      );
    };
  }
  else {
    require mro;
    constant->import( OLD_MRO => 0 );
    *DBIx::Class::_Util::get_real_pkg_gen = \&mro::get_pkg_gen;
  }

  # Both of these are no longer used for anything. However bring
  # them back after they were purged in 08a8d8f1, as there appear
  # to be outfits with *COPY PASTED* pieces of lib/DBIx/Class/Storage/*
  # in their production codebases. There is no point in breaking these
  # if whatever they used actually continues to work
  my $warned;
  my $sigh = sub {

    require Carp;
    my $cluck = "The @{[ (caller(1))[3] ]} constant is no more - adjust your code" . Carp::longmess();

    warn $cluck unless $warned->{$cluck}++;

    0;
  };
  sub DBICTEST () { &$sigh }
  sub PEEPEENESS () { &$sigh }
}

# FIXME - this is not supposed to be here
# Carp::Skip to the rescue soon
use DBIx::Class::Carp '^DBIx::Class|^DBICTest';

use B ();
use Carp 'croak';
use Storable 'nfreeze';
use Scalar::Util qw(weaken blessed reftype refaddr);
use Sub::Quote qw(qsub);
use Sub::Name ();
use attributes ();

# Already correctly prototyped: perlbrew exec perl -MStorable -e 'warn prototype \&Storable::dclone'
BEGIN { *deep_clone = \&Storable::dclone }

use base 'Exporter';
our @EXPORT_OK = qw(
  sigwarn_silencer modver_gt_or_eq modver_gt_or_eq_and_lt
  fail_on_internal_wantarray fail_on_internal_call
  refdesc refcount hrefaddr set_subname describe_class_methods
  scope_guard detected_reinvoked_destructor
  is_exception dbic_internal_try visit_namespaces
  quote_sub qsub perlstring serialize deep_clone dump_value uniq
  parent_dir mkdir_p
  UNRESOLVABLE_CONDITION
);

use constant UNRESOLVABLE_CONDITION => \ '1 = 0';

BEGIN {
  # add preliminary attribute support
  # FIXME FIXME FIXME
  # To be revisited when Moo with proper attr support ships
  Sub::Quote->VERSION(2.002);
}
# Override forcing no_defer, and adding naming consistency checks
sub quote_sub {
  Carp::confess( "Anonymous quoting not supported by the DBIC sub_quote override - supply a sub name" ) if
    @_ < 2
      or
    ! defined $_[1]
      or
    length ref $_[1]
  ;

  Carp::confess( "The DBIC sub_quote override expects sub name '$_[0]' to be fully qualified" )
    unless $_[0] =~ /::/;

  Carp::confess( "The DBIC sub_quote override expects the sub name '$_[0]' to match the supplied 'package' argument" ) if
    $_[3]
      and
    defined $_[3]->{package}
      and
    index( $_[0], $_[3]->{package} ) != 0
  ;

  my @caller = caller(0);
  my $sq_opts = {
    package => $caller[0],
    hints => $caller[8],
    warning_bits => $caller[9],
    hintshash => $caller[10],
    %{ $_[3] || {} },

    # explicitly forced for everything
    no_defer => 1,
  };

  my $cref = Sub::Quote::quote_sub( $_[0], $_[1], $_[2]||{}, $sq_opts );

  # FIXME FIXME FIXME
  # To be revisited when Moo with proper attr support ships
  if(
    # external application does not work on things like :prototype(...), :lvalue, etc
    my @attrs = grep {
      $_ !~ /^[a-z]/
        or
      Carp::confess( "The DBIC sub_quote override does not support applying of reserved attribute '$_'" )
    } @{ $sq_opts->{attributes} || []}
  ) {
    Carp::confess( "The DBIC sub_quote override does not allow mixing 'attributes' with 'no_install'" )
      if $sq_opts->{no_install};

    # might be different from $sq_opts->{package};
    my ($install_into) = $_[0] =~ /(.+)::[^:]+$/;

    attributes->import( $install_into, $cref, @attrs );
  }

  $cref;
}

sub sigwarn_silencer ($) {
  my $pattern = shift;

  croak "Expecting a regexp" if ref $pattern ne 'Regexp';

  my $orig_sig_warn = $SIG{__WARN__} || sub { CORE::warn(@_) };

  return sub { &$orig_sig_warn unless $_[0] =~ $pattern };
}

sub perlstring ($) { q{"}. quotemeta( shift ). q{"} };

sub hrefaddr ($) { sprintf '0x%x', &refaddr||0 }

sub refdesc ($) {
  croak "Expecting a reference" if ! length ref $_[0];

  # be careful not to trigger stringification,
  # reuse @_ as a scratch-pad
  sprintf '%s%s(0x%x)',
    ( defined( $_[1] = blessed $_[0]) ? "$_[1]=" : '' ),
    reftype $_[0],
    refaddr($_[0]),
  ;
}

sub refcount ($) {
  croak "Expecting a reference" if ! length ref $_[0];

  # No tempvars - must operate on $_[0], otherwise the pad
  # will count as an extra ref
  B::svref_2object($_[0])->REFCNT;
}

sub visit_namespaces {
  my $args = { (ref $_[0]) ? %{$_[0]} : @_ };

  my $visited_count = 1;

  # A package and a namespace are subtly different things
  $args->{package} ||= 'main';
  $args->{package} = 'main' if $args->{package} =~ /^ :: (?: main )? $/x;
  $args->{package} =~ s/^:://;

  if ( $args->{action}->($args->{package}) ) {
    my $ns =
      ( ($args->{package} eq 'main') ? '' :  $args->{package} )
        .
      '::'
    ;

    $visited_count += visit_namespaces( %$args, package => $_ ) for
      grep
        # this happens sometimes on %:: traversal
        { $_ ne '::main' }
        map
          { $_ =~ /^(.+?)::$/ ? "$ns$1" : () }
          do { no strict 'refs'; keys %$ns }
    ;
  }

  $visited_count;
}

# FIXME In another life switch this to a polyfill like the one in namespace::clean
sub set_subname ($$) {

  # fully qualify name
  splice @_, 0, 1, caller(0) . "::$_[0]"
    if $_[0] !~ /::|'/;

  &Sub::Name::subname;
}

sub serialize ($) {
  local $Storable::canonical = 1;
  nfreeze($_[0]);
}

sub uniq {
  my( %seen, $seen_undef, $numeric_preserving_copy );
  grep { not (
    defined $_
      ? $seen{ $numeric_preserving_copy = $_ }++
      : $seen_undef++
  ) } @_;
}

my $dd_obj;
sub dump_value ($) {
  local $Data::Dumper::Indent = 1
    unless defined $Data::Dumper::Indent;

  my $dump_str = (
    $dd_obj
      ||=
    do {
      require Data::Dumper;
      my $d = Data::Dumper->new([])
        ->Purity(0)
        ->Pad('')
        ->Useqq(1)
        ->Terse(1)
        ->Freezer('')
        ->Quotekeys(0)
        ->Bless('bless')
        ->Pair(' => ')
        ->Sortkeys(1)
        ->Deparse(1)
      ;

      $d->Sparseseen(1) if modver_gt_or_eq (
        'Data::Dumper', '2.136'
      );

      $d;
    }
  )->Values([$_[0]])->Dump;

  $dd_obj->Reset->Values([]);

  $dump_str;
}

sub scope_guard (&) {
  croak 'Calling scope_guard() in void context makes no sense'
    if ! defined wantarray;

  # no direct blessing of coderefs - DESTROY is buggy on those
  bless [ $_[0] ], 'DBIx::Class::_Util::ScopeGuard';
}
{
  package #
    DBIx::Class::_Util::ScopeGuard;

  sub DESTROY {
    &DBIx::Class::_Util::detected_reinvoked_destructor;

    local $@ if DBIx::Class::_ENV_::UNSTABLE_DOLLARAT;

    eval {
      $_[0]->[0]->();
      1;
    }
      or
    Carp::cluck(
      "Execution of scope guard $_[0] resulted in the non-trappable exception:\n\n$@"
    );
  }
}


sub is_exception ($) {
  my $e = $_[0];

  # FIXME
  # this is not strictly correct - an eval setting $@ to undef
  # is *not* the same as an eval setting $@ to ''
  # but for the sake of simplicity assume the following for
  # the time being
  return 0 unless defined $e;

  my ($not_blank, $suberror);
  {
    local $SIG{__DIE__} if $SIG{__DIE__};
    local $@;
    eval {
      # The ne() here is deliberate - a plain length($e), or worse "$e" ne
      # will entirely obviate the need for the encolsing eval{}, as the
      # condition we guard against is a missing fallback overload
      $not_blank = ( $e ne '' );
      1;
    } or $suberror = $@;
  }

  if (defined $suberror) {
    if (length (my $class = blessed($e) )) {
      carp_unique( sprintf(
        'External exception class %s implements partial (broken) overloading '
      . 'preventing its instances from being used in simple ($x eq $y) '
      . 'comparisons. Given Perl\'s "globally cooperative" exception '
      . 'handling this type of brokenness is extremely dangerous on '
      . 'exception objects, as it may (and often does) result in silent '
      . '"exception substitution". DBIx::Class tries to work around this '
      . 'as much as possible, but other parts of your software stack may '
      . 'not be even aware of this. Please submit a bugreport against the '
      . 'distribution containing %s and in the meantime apply a fix similar '
      . 'to the one shown at %s, in order to ensure your exception handling '
      . 'is saner application-wide. What follows is the actual error text '
      . "as generated by Perl itself:\n\n%s\n ",
        $class,
        $class,
        'http://v.gd/DBIC_overload_tempfix/',
        $suberror,
      ));

      # workaround, keeps spice flowing
      $not_blank = !!( length $e );
    }
    else {
      # not blessed yet failed the 'ne'... this makes 0 sense...
      # just throw further
      die $suberror
    }
  }
  elsif (
    # a ref evaluating to '' is definitively a "null object"
    ( not $not_blank )
      and
    length( my $class = ref $e )
  ) {
    carp_unique( sprintf(
      "Objects of external exception class '%s' stringify to '' (the "
    . 'empty string), implementing the so called null-object-pattern. '
    . 'Given Perl\'s "globally cooperative" exception handling using this '
    . 'class of exceptions is extremely dangerous, as it may (and often '
    . 'does) result in silent discarding of errors. DBIx::Class tries to '
    . 'work around this as much as possible, but other parts of your '
    . 'software stack may not be even aware of the problem. Please submit '
    . 'a bugreport against the distribution containing %s',

      ($class) x 2,
    ));

    $not_blank = 1;
  }

  return $not_blank;
}

{
  my $callstack_state;

  # Recreate the logic of try(), while reusing the catch()/finally() as-is
  #
  # FIXME: We need to move away from Try::Tiny entirely (way too heavy and
  # yes, shows up ON TOP of profiles) but this is a batle for another maint
  sub dbic_internal_try (&;@) {

    my $try_cref = shift;
    my $catch_cref = undef;  # apparently this is a thing... https://rt.perl.org/Public/Bug/Display.html?id=119311

    for my $arg (@_) {

      if( ref($arg) eq 'Try::Tiny::Catch' ) {

        croak 'dbic_internal_try() may not be followed by multiple catch() blocks'
          if $catch_cref;

        $catch_cref = $$arg;
      }
      elsif ( ref($arg) eq 'Try::Tiny::Finally' ) {
        croak 'dbic_internal_try() does not support finally{}';
      }
      else {
        croak(
          'dbic_internal_try() encountered an unexpected argument '
        . "'@{[ defined $arg ? $arg : 'UNDEF' ]}' - perhaps "
        . 'a missing semi-colon before or ' # trailing space important
        );
      }
    }

    my $wantarray = wantarray;
    my $preexisting_exception = $@;

    my @ret;
    my $all_good = eval {
      $@ = $preexisting_exception;

      local $callstack_state->{in_internal_try} = 1
        unless $callstack_state->{in_internal_try};

      # always unset - someone may have snuck it in
      local $SIG{__DIE__} if $SIG{__DIE__};

      if( $wantarray ) {
        @ret = $try_cref->();
      }
      elsif( defined $wantarray ) {
        $ret[0] = $try_cref->();
      }
      else {
        $try_cref->();
      }

      1;
    };

    my $exception = $@;
    $@ = $preexisting_exception;

    if ( $all_good ) {
      return $wantarray ? @ret : $ret[0]
    }
    elsif ( $catch_cref ) {
      for ( $exception ) {
        return $catch_cref->($exception);
      }
    }

    return;
  }

  sub in_internal_try { !! $callstack_state->{in_internal_try} }
}

{
  my $destruction_registry = {};

  sub DBIx::Class::__Util_iThreads_handler__::CLONE {
    %$destruction_registry = map {
      (defined $_)
        ? ( refaddr($_) => $_ )
        : ()
    } values %$destruction_registry;

    weaken($_) for values %$destruction_registry;

    # Dummy NEXTSTATE ensuring the all temporaries on the stack are garbage
    # collected before leaving this scope. Depending on the code above, this
    # may very well be just a preventive measure guarding future modifications
    undef;
  }

  # This is almost invariably invoked from within DESTROY
  # throwing exceptions won't work
  sub detected_reinvoked_destructor {

    # quick "garbage collection" pass - prevents the registry
    # from slowly growing with a bunch of undef-valued keys
    defined $destruction_registry->{$_} or delete $destruction_registry->{$_}
      for keys %$destruction_registry;

    if (! length ref $_[0]) {
      printf STDERR '%s() expects a blessed reference %s',
        (caller(0))[3],
        Carp::longmess,
      ;
      return undef; # don't know wtf to do
    }
    elsif (! defined $destruction_registry->{ my $addr = refaddr($_[0]) } ) {
      weaken( $destruction_registry->{$addr} = $_[0] );
      return 0;
    }
    else {
      carp_unique ( sprintf (
        'Preventing *MULTIPLE* DESTROY() invocations on %s - an *EXTREMELY '
      . 'DANGEROUS* condition which is *ALMOST CERTAINLY GLOBAL* within your '
      . 'application, affecting *ALL* classes without active protection against '
      . 'this. Diagnose and fix the root cause ASAP!!!%s',
      refdesc $_[0],
        ( ( $INC{'Devel/StackTrace.pm'} and ! do { local $@; eval { Devel::StackTrace->VERSION(2) } } )
          ? " (likely culprit Devel::StackTrace\@@{[ Devel::StackTrace->VERSION ]} found in %INC, http://is.gd/D_ST_refcap)"
          : ''
        )
      ));

      return 1;
    }
  }
}

my $module_name_rx = qr/ \A [A-Z_a-z] [0-9A-Z_a-z]* (?: :: [0-9A-Z_a-z]+ )* \z /x;
my $ver_rx =         qr/ \A [0-9]+ (?: \. [0-9]+ )* (?: \_ [0-9]+ )*        \z /x;

sub modver_gt_or_eq ($$) {
  my ($mod, $ver) = @_;

  croak "Nonsensical module name supplied"
    if ! defined $mod or $mod !~ $module_name_rx;

  croak "Nonsensical minimum version supplied"
    if ! defined $ver or $ver !~ $ver_rx;

  no strict 'refs';
  my $ver_cache = ${"${mod}::__DBIC_MODULE_VERSION_CHECKS__"} ||= ( $mod->VERSION
    ? {}
    : croak "$mod does not seem to provide a version (perhaps it never loaded)"
  );

  ! defined $ver_cache->{$ver}
    and
  $ver_cache->{$ver} = do {

    local $SIG{__WARN__} = sigwarn_silencer( qr/\Qisn't numeric in subroutine entry/ )
      if SPURIOUS_VERSION_CHECK_WARNINGS;

    local $SIG{__DIE__} if $SIG{__DIE__};
    local $@;
    eval { $mod->VERSION($ver) } ? 1 : 0;
  };

  $ver_cache->{$ver};
}

sub modver_gt_or_eq_and_lt ($$$) {
  my ($mod, $v_ge, $v_lt) = @_;

  croak "Nonsensical maximum version supplied"
    if ! defined $v_lt or $v_lt !~ $ver_rx;

  return (
    modver_gt_or_eq($mod, $v_ge)
      and
    ! modver_gt_or_eq($mod, $v_lt)
  ) ? 1 : 0;
}

{
  # FIXME - should be a private my(), but I'm too uncertain whether
  # all bases are covered
  our $describe_class_query_cache;

  sub describe_class_methods {

    croak "Expecting a class name"
      if not defined $_[0] or $_[0] !~ $module_name_rx;

    # use a cache on old MRO, since while we are recursing in this function
    # nothing can possibly change (the speedup is immense)
    # (yes, people could be tie()ing the stash and adding methods on access
    # but there is a limit to how much crazy can be supported here)
    #
    # we use the cache for linear_isa lookups on new MRO as well - it adds
    # a *tiny* speedup, and simplifies the code a lot
    #
    local $mro_recursor_stack->{cache} = {}
      unless $mro_recursor_stack->{cache};

    my $my_gen = 0;

    $my_gen += get_real_pkg_gen($_) for (
      'UNIVERSAL',
      my ($class, @my_ISA) = @{
        $mro_recursor_stack->{cache}{$_[0]}{linear_isa}
          ||=
        mro::get_linear_isa($_[0])
      }
    );

    my $slot = $describe_class_query_cache->{$class} ||= {};

    unless ( ($slot->{cumulative_gen}||0) == $my_gen ) {

      # reset
      %$slot = (
        class => $class,
        isa => [ @my_ISA ], # copy before we shove UNIVERSAL into it
        mro => {
          type => mro::get_mro($class),
        },
        cumulative_gen => $my_gen,
      );
      $slot->{mro}{is_c3} = ($slot->{mro}{type} eq 'c3') ? 1 : 0;

      push @my_ISA, 'UNIVERSAL';

      # ensure the cache is populated for the parents, code below can then
      # efficiently operate over the query_cache directly
      for (reverse @my_ISA) {
        my ($parent_gen, @parent_ISA);

        # and even more skips before calling out recursively
        describe_class_methods($_) unless (
          $describe_class_query_cache->{$_}{cumulative_gen}
            and
          $parent_gen = get_real_pkg_gen($_)
            and
          (
            (
              (undef, @parent_ISA) = @{
                $mro_recursor_stack->{cache}{$_}{linear_isa}
                  ||=
                mro::get_linear_isa($_)
              }
            ) == 1
              or
            do {
              $parent_gen += get_real_pkg_gen($_) for @parent_ISA;
              1;
            }
          )
            and
          $describe_class_query_cache->{$_}{cumulative_gen} == $parent_gen
        );
      }

      my ($methods_seen_via_ISA_on_old_mro, $current_node_refaddr);
      no strict 'refs';

      # combine full ISA-order inherited and local method list into a
      # "shadowing stack"

      (
        $current_node_refaddr = refaddr($_)

          and

        # on complex MI herarchies the method can be anywhere in the
        # shadow stack - look through the entire slot, not just [0]
        ( ! grep {
          refaddr($_) == $current_node_refaddr
        } @{ $slot->{methods}{ $_->{name} } || [] } )

          and

        unshift @{ $slot->{methods}{$_->{name}} }, $_

          and

        @{ $slot->{methods}{$_->{name}} } > 1

          and

        $slot->{methods_with_supers}{$_->{name}} = $slot->{methods}{$_->{name}}

      ) for (

        # what describe_class_methods for @my_ISA produced above
        ( map { $_->[0] } map {
          values %{ $describe_class_query_cache->{$_}{methods} }
        } reverse @my_ISA ),

        # our own non-cleaned subs + their attributes
        ( map {
          (
            # these 2 OR-ed checks are sufficient for 5.10+
            (
              ref(\ "${class}::"->{$_} ) ne 'GLOB'
                or
              defined( *{ "${class}::"->{$_} }{CODE} )
            )
              and
            # need to account for dummy helper crefs under OLD_MRO
            (
              ! DBIx::Class::_ENV_::OLD_MRO
                or
              (
                $methods_seen_via_ISA_on_old_mro ||= do {
                  my $rv = {};
                  $rv->{$_->{name}}->{ refaddr( \&{ "$_->{via_class}::$_->{name}"} ) } = 1 for
                    map { @$_ } map
                      { values %{ $describe_class_query_cache->{$_}{methods} } }
                      @my_ISA;
                  $rv;
                }
                  and
                (
                  ! $methods_seen_via_ISA_on_old_mro->{$_}
                    or
                  ! $methods_seen_via_ISA_on_old_mro->{$_}{ refaddr( \&{"${class}::${_}"} ) }
                )
              )
            )
          ) ? {
              via_class => $class,
              name => $_,
              attributes => { map { $_ => 1 } @{
                $mro_recursor_stack->{cache}{attrs}{ refaddr \&{"${class}::${_}"} }
                  ||=
                [ attributes::get( \&{"${class}::${_}"} ) ]
              } },
            }
            : ()
        } keys %{"${class}::"} )
      );


      # recalculate the pkg_gen on newer perls under Taint mode,
      # because of shit like:
      # perl -T -Mmro -e 'package Foo; sub bar {}; defined( *{ "Foo::"->{bar}}{CODE} ) and warn mro::get_pkg_gen("Foo") for (1,2,3)'
      #
      if (
        ! DBIx::Class::_ENV_::OLD_MRO
          and
        ${^TAINT}
      ) {

        $slot->{cumulative_gen} = 0;
        $slot->{cumulative_gen} += get_real_pkg_gen($_)
          for $class, @my_ISA;
      }
    }

    # RV
    +{ %$slot };
  }
}


#
# Why not just use some higher-level module or at least File::Spec here?
# Because:
# 1)  This is a *very* rarely used function, and the deptree is large
#     enough already as it is
#
# 2)  (more importantly) Our tooling is utter shit in this area. There
#     is no comprehensive support for UNC paths in PathTools and there
#     are also various small bugs in representation across different
#     path-manipulation CPAN offerings.
#
# Since this routine is strictly used for logical path processing (it
# *must* be able to work with not-yet-existing paths), use this seemingly
# simple but I *think* complete implementation to feed to other consumers
#
# If bugs are ever uncovered in this routine, *YOU ARE URGED TO RESIST*
# the impulse to bring in an external dependency. During runtime there
# is exactly one spot that could potentially maybe once in a blue moon
# use this function. Keep it lean.
#
sub parent_dir ($) {
  ( $_[0] =~ m{  [\/\\]  ( \.{0,2} ) ( [\/\\]* ) \z }x )
    ? (
      $_[0]
        .
      ( ( length($1) and ! length($2) ) ? '/' : '' )
        .
      '../'
    )
    : (
      require File::Spec
        and
      File::Spec->catpath (
        ( File::Spec->splitpath( "$_[0]" ) )[0,1],
        '/',
      )
    )
  ;
}

sub mkdir_p ($) {
  require File::Path;
  # do not ask for a recent version, use 1.x API calls
  File::Path::mkpath([ "$_[0]" ]);  # File::Path does not like objects
}


{
  my $list_ctx_ok_stack_marker;

  sub fail_on_internal_wantarray () {
    return if $list_ctx_ok_stack_marker;

    if (! defined wantarray) {
      croak('fail_on_internal_wantarray() needs a tempvar to save the stack marker guard');
    }

    my $cf = 1;
    while ( ( (CORE::caller($cf+1))[3] || '' ) =~ / :: (?:

      # these are public API parts that alter behavior on wantarray
      search | search_related | slice | search_literal

        |

      # these are explicitly prefixed, since we only recognize them as valid
      # escapes when they come from the guts of CDBICompat
      CDBICompat .*? :: (?: search_where | retrieve_from_sql | retrieve_all )

    ) $/x ) {
      $cf++;
    }

    my ($fr, $want, $argdesc);
    {
      package DB;
      $fr = [ CORE::caller($cf) ];
      $want = ( CORE::caller($cf-1) )[5];
      $argdesc = ref $DB::args[0]
        ? DBIx::Class::_Util::refdesc($DB::args[0])
        : 'non '
      ;
    };

    if (
      $want and $fr->[0] =~ /^(?:DBIx::Class|DBICx::)/
    ) {
      DBIx::Class::Exception->throw( sprintf (
        "Improper use of %s instance in list context at %s line %d\n\n    Stacktrace starts",
        $argdesc, @{$fr}[1,2]
      ), 'with_stacktrace');
    }

    weaken( $list_ctx_ok_stack_marker = my $mark = [] );

    $mark;
  }
}

sub fail_on_internal_call {
  my ($fr, $argdesc);
  {
    package DB;
    $fr = [ CORE::caller(1) ];
    $argdesc = ref $DB::args[0]
      ? DBIx::Class::_Util::refdesc($DB::args[0])
      : ( $DB::args[0] . '' )
    ;
  };

  my @fr2;
  # need to make allowance for a proxy-yet-direct call
  my $check_fr = (
    $fr->[0] eq 'DBIx::Class::ResultSourceProxy'
      and
    @fr2 = (CORE::caller(2))
      and
    (
      ( $fr->[3] =~ /([^:])+$/ )[0]
        eq
      ( $fr2[3] =~ /([^:])+$/ )[0]
    )
  )
    ? \@fr2
    : $fr
  ;

  if (
    $argdesc
      and
    $check_fr->[0] =~ /^(?:DBIx::Class|DBICx::)/
      and
    $check_fr->[1] !~ /\b(?:CDBICompat|ResultSetProxy)\b/  # no point touching there
  ) {
    DBIx::Class::Exception->throw( sprintf (
      "Illegal internal call of indirect proxy-method %s() with argument '%s': examine the last lines of the proxy method deparse below to determine what to call directly instead at %s on line %d\n\n%s\n\n    Stacktrace starts",
      $fr->[3], $argdesc, @{$fr}[1,2], ( $fr->[6] || do {
        require B::Deparse;
        no strict 'refs';
        B::Deparse->new->coderef2text(\&{$fr->[3]})
      }),
    ), 'with_stacktrace');
  }
}

1;