X-Git-Url: http://git.vpit.fr/?a=blobdiff_plain;f=lib%2FScope%2FUpper.pm;h=377e434e5bd8adc8c6e2be7e2bd4f20b692155c8;hb=cb2377339e35cfbadcaf35f75434972bbaf741bc;hp=84de02eea6ebf8befe98320881ff7d27f3d421fa;hpb=44bbbdcdafa5707a753abb9de5c5d01cd7388880;p=perl%2Fmodules%2FScope-Upper.git

diff --git a/lib/Scope/Upper.pm b/lib/Scope/Upper.pm
index 84de02e..377e434 100644
--- a/lib/Scope/Upper.pm
+++ b/lib/Scope/Upper.pm
@@ -9,61 +9,89 @@ Scope::Upper - Act on upper scopes.
 
 =head1 VERSION
 
-Version 0.10
+Version 0.17
 
 =cut
 
 our $VERSION;
 BEGIN {
- $VERSION = '0.10';
+ $VERSION = '0.17';
 }
 
 =head1 SYNOPSIS
 
-    package X;
+L</reap>, L</localize>, L</localize_elem>, L</localize_delete> and L</WORDS> :
 
-    use Scope::Upper qw/reap localize localize_elem localize_delete :words/;
+    package Scope;
 
-    sub desc { shift->{desc} }
+    use Scope::Upper qw<reap localize localize_elem localize_delete :words>;
 
-    sub set_tag {
-     my ($desc) = @_;
+    sub new {
+     my ($class, $name) = @_;
 
-     # First localize $x so that it gets destroyed last
-     localize '$x' => bless({ desc => $desc }, __PACKAGE__) => UP; # one scope up
+     localize '$tag' => bless({ name => $name }, $class) => UP;
 
-     reap sub {
-      my $pkg = caller;
-      my $x = do { no strict 'refs'; ${$pkg.'::x'} }; # Get the $x in the scope
-      print $x->desc . ": done\n";
-     } => SCOPE 1; # same as UP here
+     reap { print Scope->tag->name, ": end\n" } UP;
+    }
+
+    # Get the tag stored in the caller namespace
+    sub tag {
+     my $l   = 0;
+     my $pkg = __PACKAGE__;
+     $pkg    = caller $l++ while $pkg eq __PACKAGE__;
+
+     no strict 'refs';
+     ${$pkg . '::tag'};
+    }
 
+    sub name { shift->{name} }
+
+    # Locally capture warnings and reprint them with the name prefixed
+    sub catch {
      localize_elem '%SIG', '__WARN__' => sub {
-      my $pkg = caller;
-      my $x = do { no strict 'refs'; ${$pkg.'::x'} }; # Get the $x in the scope
-      CORE::warn($x->desc . ': ' . join('', @_));
-     } => UP CALLER 0; # same as UP here
+      print Scope->tag->name, ': ', @_;
+     } => UP;
+    }
 
-     # delete last @ARGV element
-     localize_delete '@ARGV', -1 => UP SUB HERE; # same as UP here
+    # Locally clear @INC
+    sub private {
+     for (reverse 0 .. $#INC) {
+      # First UP is the for loop, second is the sub boundary
+      localize_delete '@INC', $_ => UP UP;
+     }
     }
 
-    package Y;
+    ...
+
+    package UserLand;
 
     {
-     X::set_tag('pie');
-     # $x is now a X object, and @ARGV has one element less
-     warn 'what'; # warns "pie: what at ..."
-     ...
-    } # "pie: done" is printed
+     Scope->new("top");      # initializes $UserLand::tag
+
+     {
+      Scope->catch;
+      my $one = 1 + undef;   # prints "top: Use of uninitialized value..."
+
+      {
+       Scope->private;
+       eval { require Cwd };
+       print $@;             # prints "Can't locate Cwd.pm in @INC (@INC contains:) at..."
+      }
+
+      require Cwd;           # loads Cwd.pm
+     }
+
+    }                        # prints "top: done"
 
-    package Z;
+L</unwind> and L</want_at> :
 
-    use Scope::Upper qw/unwind want_at :words/;
+    package Try;
+
+    use Scope::Upper qw<unwind want_at :words>;
 
     sub try (&) {
      my @result = shift->();
-     my $cx = SUB UP SUB;
+     my $cx = SUB UP; # Point to the sub above this one
      unwind +(want_at($cx) ? @result : scalar @result) => $cx;
     }
 
@@ -71,13 +99,34 @@ BEGIN {
 
     sub zap {
      try {
+      my @things = qw<a b c>;
       return @things; # returns to try() and then outside zap()
       # not reached
-     }
+     };
      # not reached
     }
 
-    my @what = zap(); # @what contains @things
+    my @stuff = zap(); # @stuff contains qw<a b c>
+    my $stuff = zap(); # $stuff contains 3
+
+L</uplevel> :
+
+    package Uplevel;
+
+    use Scope::Upper qw<uplevel CALLER>;
+
+    sub target {
+     faker(@_);
+    }
+
+    sub faker {
+     uplevel {
+      my $sub = (caller 0)[3];
+      print "$_[0] from $sub()";
+     } @_ => CALLER(1);
+    }
+
+    target('hello'); # "hello from Uplevel::target()"
 
 =head1 DESCRIPTION
 
@@ -96,7 +145,11 @@ localize variables, array/hash values or deletions of elements in higher context
 
 =item *
 
-return values immediately to an upper level with L</unwind>, and know which context was in use then with L</want_at>.
+return values immediately to an upper level with L</unwind>, and know which context was in use then with L</want_at> ;
+
+=item *
+
+execute a subroutine in the setting of an upper subroutine stack frame with L</uplevel>.
 
 =back
 
@@ -117,11 +170,11 @@ BEGIN {
 
 =head2 C<reap $callback, $context>
 
-Add a destructor that calls C<$callback> (in void context) when the upper scope represented by C<$context> ends.
+Adds a destructor that calls C<$callback> (in void context) when the upper scope represented by C<$context> ends.
 
 =head2 C<localize $what, $value, $context>
 
-A C<local> delayed to the time of first return into the upper scope denoted by C<$context>.
+Introduces a C<local> delayed to the time of first return into the upper scope denoted by C<$context>.
 C<$what> can be :
 
 =over 4
@@ -143,8 +196,8 @@ For example,
 will set C<$x> to a reference to the string C<'foo'>.
 Other sigils (C<'@'>, C<'%'>, C<'&'> and C<'*'>) require C<$value> to be a reference of the corresponding type.
 
-When the symbol is given by a string, it is resolved when the actual localization takes place and not when C<localize> is called.
-Thus, if the symbol name is not qualified, it will refer to the variable in the package where the localization actually takes place and not in the one where the C<localize> call was compiled.
+When the symbol is given by a string, it is resolved when the actual localization takes place and not when L</localize> is called.
+Thus, if the symbol name is not qualified, it will refer to the variable in the package where the localization actually takes place and not in the one where the L</localize> call was compiled.
 For example,
 
     {
@@ -161,6 +214,7 @@ For example,
     }
 
 will localize C<$Tool::tag> and not C<$Scope::tag>.
+If you want the other behaviour, you just have to specify C<$what> as a glob or a qualified name.
 
 Note that if C<$what> is a string denoting a variable that wasn't declared beforehand, the relevant slot will be vivified as needed and won't be deleted from the glob when the localization ends.
 This situation never arises with C<local> because it only compiles when the localized variable is already declared.
@@ -170,15 +224,16 @@ Although I believe it shouldn't be a problem as glob slots definedness is pretty
 
 =head2 C<localize_elem $what, $key, $value, $context>
 
-Similar to L</localize> but for array and hash elements.
-If C<$what> is a glob, the slot to fill is determined from which type of reference C<$value> is ; otherwise it's inferred from the sigil.
+Introduces a C<local $what[$key] = $value> or C<local $what{$key} = $value> delayed to the time of first return into the upper scope denoted by C<$context>.
+Unlike L</localize>, C<$what> must be a string and the type of localization is inferred from its sigil.
+The two only valid types are array and hash ; for anything besides those, L</localize_elem> will throw an exception.
 C<$key> is either an array index or a hash key, depending of which kind of variable you localize.
 
-Just like for L</localize>, when C<$what> is a string pointing to an undeclared variable, it will be vivified but the variable itself will be empty when the localization ends (although it will still exist in its parent glob).
+If C<$what> is a string pointing to an undeclared variable, the variable will be vivified as soon as the localization occurs and emptied when it ends, although it will still exist in its glob.
 
 =head2 C<localize_delete $what, $key, $context>
 
-Similiar to L</localize>, but for deleting variables or array/hash elements.
+Introduces the deletion of a variable or an array/hash element delayed to the time of first return into the upper scope denoted by C<$context>.
 C<$what> can be:
 
 =over 4
@@ -201,7 +256,7 @@ C<$key> is ignored.
 
 =head2 C<unwind @values, $context>
 
-Returns C<@values> I<from> the context pointed by C<$context>, i.e. from the subroutine, eval or format just above C<$context>, and immediately restart the program flow at this point - thus effectively returning to (or from, depending on how you see it) an upper context.
+Returns C<@values> I<from> the context pointed by C<$context>, i.e. from the subroutine, eval or format at or just above C<$context>, and immediately restart the program flow at this point - thus effectively returning to an upper scope.
 
 The upper context isn't coerced onto C<@values>, which is hence always evaluated in list context.
 This means that
@@ -217,7 +272,7 @@ You can use L</want_at> to handle these cases.
 
 =head2 C<want_at $context>
 
-Like C<wantarray>, but for the subroutine/eval/format just above C<$context>.
+Like C<wantarray>, but for the subroutine/eval/format at or just above C<$context>.
 
 The previous example can then be "corrected" :
 
@@ -229,6 +284,75 @@ The previous example can then be "corrected" :
 
 will rightfully set C<$num> to C<26>.
 
+=head2 C<uplevel $code, @args, $context>
+
+Executes the code reference C<$code> with arguments C<@args> as if it were located at the subroutine stack frame pointed by C<$context>, effectively fooling C<caller> and C<die> into believing that the call actually happened higher in the stack.
+The code is executed in the context of the C<uplevel> call, and what it returns is returned as-is by C<uplevel>.
+
+    sub target {
+     faker(@_);
+    }
+
+    sub faker {
+     uplevel {
+      map { 1 / $_ } @_;
+     } @_ => CALLER(1);
+    }
+
+    my @inverses = target(1, 2, 4); # @inverses contains (0, 0.5, 0.25)
+    my $count    = target(1, 2, 4); # $count is 3
+
+L<Sub::Uplevel> also implements a pure-Perl version of C<uplevel>.
+Both are identical, with the following caveats :
+
+=over 4
+
+=item *
+
+The L<Sub::Uplevel> implementation of C<uplevel> may execute a code reference in the context of B<any> upper stack frame.
+The L<Scope::Upper> version can only uplevel to a B<subroutine> stack frame, and will croak if you try to target an C<eval> or a format.
+
+=item *
+
+Exceptions thrown from the code called by this version of C<uplevel> will not be caught by C<eval> blocks between the target frame and the uplevel call, while they will for L<Sub::Uplevel>'s version.
+This means that :
+
+    eval {
+     sub {
+      local $@;
+      eval {
+       sub {
+        uplevel { die 'wut' } CALLER(2); # for Scope::Upper
+        # uplevel(3, sub { die 'wut' })  # for Sub::Uplevel
+       }->();
+      };
+      print "inner block: $@";
+      $@ and exit;
+     }->();
+    };
+    print "outer block: $@";
+
+will print "inner block: wut..." with L<Sub::Uplevel> and "outer block: wut..." with L<Scope::Upper>.
+
+=item *
+
+L<Sub::Uplevel> globally overrides the Perl keyword C<caller>, while L<Scope::Upper> does not.
+
+=back
+
+A simple wrapper lets you mimic the interface of L<Sub::Uplevel/uplevel> :
+
+    use Scope::Upper;
+
+    sub uplevel {
+     my $frame = shift;
+     my $code  = shift;
+     my $cxt   = Scope::Upper::CALLER($frame);
+     &Scope::Upper::uplevel($code => @_ => $cxt);
+    }
+
+Albeit the three exceptions listed above, it passes all the tests of L<Sub::Uplevel>.
+
 =head1 CONSTANTS
 
 =head2 C<SU_THREADSAFE>
@@ -321,26 +445,29 @@ Where L</localize>, L</localize_elem> and L</localize_delete> act depending on t
     # $cxt = SCOPE(4), UP SUB UP SUB, or UP SUB EVAL, or UP CALLER(2), or TOP
     ...
 
-Where L</unwind> and L</want_at> point to depending on the C<$cxt>:
+Where L</unwind>, L</want_at> and L</uplevel> point to depending on the C<$cxt>:
 
     sub {
      eval {
       sub {
        {
-        unwind @things => $cxt;
+        unwind @things => $cxt;     # or uplevel { ... } $cxt;
         ...
        }
        ...
       }->(); # $cxt = SCOPE(0 .. 1), or HERE, or UP, or SUB, or CALLER(0)
       ...
-     };      # $cxt = SCOPE(2), or UP UP, or UP SUB, or EVAL, or CALLER(1)
+     };      # $cxt = SCOPE(2), or UP UP, or UP SUB, or EVAL, or CALLER(1) (*)
      ...
     }->();   # $cxt = SCOPE(3), or SUB UP SUB, or SUB EVAL, or CALLER(2)
     ...
 
+    # (*) Note that uplevel() will croak if you pass that scope frame,
+    #     because it cannot target eval scopes.
+
 =head1 EXPORT
 
-The functions L</reap>, L</localize>, L</localize_elem>, L</localize_delete>,  L</unwind> and L</want_at> are only exported on request, either individually or by the tags C<':funcs'> and C<':all'>.
+The functions L</reap>, L</localize>, L</localize_elem>, L</localize_delete>,  L</unwind>, L</want_at> and L</uplevel> are only exported on request, either individually or by the tags C<':funcs'> and C<':all'>.
 
 The constant L</SU_THREADSAFE> is also only exported on request, individually or by the tags C<':consts'> and C<':all'>.
 
@@ -348,13 +475,18 @@ Same goes for the words L</TOP>, L</HERE>, L</UP>, L</SUB>, L</EVAL>, L</SCOPE>
 
 =cut
 
-use base qw/Exporter/;
+use base qw<Exporter>;
 
 our @EXPORT      = ();
 our %EXPORT_TAGS = (
- funcs  => [ qw/reap localize localize_elem localize_delete unwind want_at/ ],
- words  => [ qw/TOP HERE UP SUB EVAL SCOPE CALLER/ ],
- consts => [ qw/SU_THREADSAFE/ ],
+ funcs  => [ qw<
+  reap
+  localize localize_elem localize_delete
+  unwind want_at
+  uplevel
+ > ],
+ words  => [ qw<TOP HERE UP SUB EVAL SCOPE CALLER> ],
+ consts => [ qw<SU_THREADSAFE> ],
 );
 our @EXPORT_OK   = map { @$_ } values %EXPORT_TAGS;
 $EXPORT_TAGS{'all'} = [ @EXPORT_OK ];
@@ -388,17 +520,29 @@ However, it's possible to hook the end of the current scope compilation with L<B
 Some rare oddities may still happen when running inside the debugger.
 It may help to use a perl higher than 5.8.9 or 5.10.0, as they contain some context-related fixes.
 
+Calling C<goto> to replace an L</uplevel>'d code frame does not work when a custom runloop is used or when debugging flags are set with C<perl -D>.
+In those two cases, L</uplevel> will look for a C<goto &sub> statement in its callback and, if there is one, throw an exception before executing the code.
+
+Moreover, in order to handle C<goto> statements properly, L</uplevel> currently has to suffer a run-time overhead proportional to the size of the the callback in every case (with a small ratio), and proportional to the size of B<all> the code executed as the result of the L</uplevel> call (including subroutine calls inside the callback) when a C<goto> statement is found in the L</uplevel> callback.
+Despite this shortcoming, this XS version of L</uplevel> should still run way faster than the pure-Perl version from L<Sub::Uplevel>.
+
 =head1 DEPENDENCIES
 
 L<XSLoader> (standard since perl 5.006).
 
 =head1 SEE ALSO
 
+L<perlfunc/local>, L<perlsub/"Temporary Values via local()">.
+
 L<Alias>, L<Hook::Scope>, L<Scope::Guard>, L<Guard>.
 
+L<Sub::Uplevel>.
+
 L<Continuation::Escape> is a thin wrapper around L<Scope::Upper> that gives you a continuation passing style interface to L</unwind>.
 It's easier to use, but it requires you to have control over the scope where you want to return.
 
+L<Scope::Escape>.
+
 =head1 AUTHOR
 
 Vincent Pit, C<< <perl at profvince.com> >>, L<http://www.profvince.com>.
@@ -426,7 +570,7 @@ Thanks to Shawn M. Moore for motivation.
 
 =head1 COPYRIGHT & LICENSE
 
-Copyright 2008,2009,2010 Vincent Pit, all rights reserved.
+Copyright 2008,2009,2010,2011 Vincent Pit, all rights reserved.
 
 This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.