This is 0.13

[perl/modules/Scope-Upper.git] / lib / Scope / Upper.pm

diff --git a/lib/Scope/Upper.pm b/lib/Scope/Upper.pm
index 988254fa5016b804443464a1fbb23fb2067aa5d9..acd566b0f7588a166d2cf460f3e7f1f76f33492b 100644 (file)
--- a/lib/Scope/Upper.pm
+++ b/lib/Scope/Upper.pm
@@ -9,61 +9,89 @@ Scope::Upper - Act on upper scopes.
 
 =head1 VERSION
 
 
 =head1 VERSION
 

-Version 0.05
+Version 0.13

 
 =cut
 
 our $VERSION;
 BEGIN {
 
 =cut
 
 our $VERSION;
 BEGIN {

- $VERSION = '0.05';
+ $VERSION = '0.13';

 }
 
 =head1 SYNOPSIS
 
 }
 
 =head1 SYNOPSIS
 

-    package X;
+L</reap>, L</localize>, L</localize_elem>, L</localize_delete> and L</WORDS> :
+
+    package Scope;

 
     use Scope::Upper qw/reap localize localize_elem localize_delete :words/;
 
 
     use Scope::Upper qw/reap localize localize_elem localize_delete :words/;
 

-    sub desc { shift->{desc} }
+    sub new {
+     my ($class, $name) = @_;
+
+     localize '$tag' => bless({ name => $name }, $class) => UP;
+
+     reap { print Scope->tag->name, ": end\n" } UP;
+    }

 
 

-    sub set_tag {
-     my ($desc) = @_;
+    # Get the tag stored in the caller namespace
+    sub tag {
+     my $l   = 0;
+     my $pkg = __PACKAGE__;
+     $pkg    = caller $l++ while $pkg eq __PACKAGE__;

 
 

-     # First localize $x so that it gets destroyed last
-     localize '$x' => bless({ desc => $desc }, __PACKAGE__) => UP; # one scope up
+     no strict 'refs';
+     ${$pkg . '::tag'};
+    }

 
 

-     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
+    sub name { shift->{name} }

 
 

+    # Locally capture warnings and reprint them with the name prefixed
+    sub catch {

      localize_elem '%SIG', '__WARN__' => sub {
      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> :
+
+    package Try;

 
     use Scope::Upper qw/unwind want_at :words/;
 
     sub try (&) {
      my @result = shift->();
 
     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;
     }
 
      unwind +(want_at($cx) ? @result : scalar @result) => $cx;
     }
 


@@ -71,28 +99,44 @@ BEGIN {
 
     sub zap {
      try {
 
     sub zap {
      try {

+      my @things = qw/a b c/;

       return @things; # returns to try() and then outside zap()
       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

 
 =head1 DESCRIPTION
 
 
 =head1 DESCRIPTION
 

-This module lets you defer actions that will take place when the control flow returns into an upper scope.
-Currently, you can hook an upper scope end, or localize variables, array/hash values or deletions of elements in higher contexts.
-You can also return to an upper level and know which context was in use then.
+This module lets you defer actions I<at run-time> that will take place when the control flow returns into an upper scope.
+Currently, you can:
+
+=over 4
+
+=item *
+
+hook an upper scope end with L</reap> ;
+
+=item *
+
+localize variables, array/hash values or deletions of elements in higher contexts with respectively L</localize>, L</localize_elem> and L</localize_delete> ;
+
+=item *
+
+return values immediately to an upper level with L</unwind>, and know which context was in use then with L</want_at>.
+
+=back

 
 =head1 FUNCTIONS
 
 In all those functions, C<$context> refers to the target scope.
 
 
 =head1 FUNCTIONS
 
 In all those functions, C<$context> refers to the target scope.
 

-You have to use one or a combination of L</WORDS> to build the C<$context> to pass to these functions.
+You have to use one or a combination of L</WORDS> to build the C<$context> passed to these functions.

 This is needed in order to ensure that the module still works when your program is ran in the debugger.
 This is needed in order to ensure that the module still works when your program is ran in the debugger.

-Don't try to use a raw value or things will get messy.
-
-The only thing you can assume is that it is an I<absolute> indicator of the frame.
-This means that you can safely store it at some point and use it when needed, and it will still denote the original scope.
+The only thing you can assume is that it is an I<absolute> indicator of the frame, which means that you can safely store it at some point and use it when needed, and it will still denote the original scope.

 
 =cut
 
 
 =cut
 


@@ -103,11 +147,11 @@ BEGIN {
 
 =head2 C<reap $callback, $context>
 
 
 =head2 C<reap $callback, $context>
 

-Add a destructor that calls C<$callback> when the upper scope represented by C<$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>
 
 
 =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
 C<$what> can be :
 
 =over 4


@@ -129,24 +173,44 @@ 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.
 
 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.
-This means that
+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,

 
 

-    sub tag { localize '$x', $_[0] => UP }
+    {
+     package Scope;
+     sub new { localize '$tag', $_[0] => UP }
+    }

 
 

-will localize in the caller's namespace.
+    {
+     package Tool;
+     {
+      Scope->new;
+      ...
+     }
+    }
+
+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.
+Although I believe it shouldn't be a problem as glob slots definedness is pretty much an implementation detail, this behaviour may change in the future if proved harmful.

 
 =back
 
 =head2 C<localize_elem $what, $key, $value, $context>
 
 
 =back
 
 =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.
 
 C<$key> is either an array index or a hash key, depending of which kind of variable you localize.
 

+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>
 
 =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
 C<$what> can be:
 
 =over 4


@@ -169,7 +233,7 @@ C<$key> is ignored.
 
 =head2 C<unwind @values, $context>
 
 
 =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>.
+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
 
 The upper context isn't coerced onto C<@values>, which is hence always evaluated in list context.
 This means that


@@ -177,6 +241,7 @@ This means that
     my $num = sub {
      my @a = ('a' .. 'z');
      unwind @a => HERE;
     my $num = sub {
      my @a = ('a' .. 'z');
      unwind @a => HERE;

+     # not reached

     }->();
 
 will set C<$num> to C<'z'>.
     }->();
 
 will set C<$num> to C<'z'>.


@@ -184,16 +249,23 @@ You can use L</want_at> to handle these cases.
 
 =head2 C<want_at $context>
 
 
 =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" :
 
     my $num = sub {
      my @a = ('a' .. 'z');
      unwind +(want_at(HERE) ? @a : scalar @a) => HERE;
 
 The previous example can then be "corrected" :
 
     my $num = sub {
      my @a = ('a' .. 'z');
      unwind +(want_at(HERE) ? @a : scalar @a) => HERE;

+     # not reached

     }->();
 
     }->();
 

-will righteously set C<$num> to C<26>.
+will rightfully set C<$num> to C<26>.
+
+=head1 CONSTANTS
+
+=head2 C<SU_THREADSAFE>
+
+True iff the module could have been built when thread-safety features.

 
 =head1 WORDS
 
 
 =head1 WORDS
 


@@ -219,10 +291,12 @@ The context of the scope just above C<$from>.
 =head3 C<SUB $from>
 
 The context of the closest subroutine above C<$from>.
 =head3 C<SUB $from>
 
 The context of the closest subroutine above C<$from>.

+Note that C<$from> is returned if it is already a subroutine context ; hence C<SUB SUB == SUB>.

 
 =head3 C<EVAL $from>
 
 The context of the closest eval above C<$from>.
 
 =head3 C<EVAL $from>
 
 The context of the closest eval above C<$from>.

+Note that C<$from> is returned if it is already an eval context ; hence C<EVAL EVAL == EVAL>.

 
 =head2 Getting a context from a level
 
 
 =head2 Getting a context from a level
 


@@ -238,10 +312,70 @@ The C<$level>-th upper context, regardless of its type.
 The context of the C<$level>-th upper subroutine/eval/format.
 It kind of corresponds to the context represented by C<caller $level>, but while e.g. C<caller 0> refers to the caller context, C<CALLER 0> will refer to the top scope in the current context.
 
 The context of the C<$level>-th upper subroutine/eval/format.
 It kind of corresponds to the context represented by C<caller $level>, but while e.g. C<caller 0> refers to the caller context, C<CALLER 0> will refer to the top scope in the current context.
 

+=head2 Examples
+
+Where L</reap> fires depending on the C<$cxt> :
+
+    sub {
+     eval {
+      sub {
+       {
+        reap \&cleanup => $cxt;
+        ...
+       }     # $cxt = SCOPE(0), or HERE
+       ...
+      }->(); # $cxt = SCOPE(1), or UP, or SUB, or CALLER, or CALLER(0)
+      ...
+     };      # $cxt = SCOPE(2), or UP UP, or UP SUB, or EVAL, or CALLER(1)
+     ...
+    }->();   # $cxt = SCOPE(3), or SUB UP SUB, or SUB EVAL, or CALLER(2)
+    ...
+
+Where L</localize>, L</localize_elem> and L</localize_delete> act depending on the C<$cxt> :
+
+    sub {
+     eval {
+      sub {
+       {
+        localize '$x' => 1 => $cxt;
+        # $cxt = SCOPE(0), or HERE
+        ...
+       }
+       # $cxt = SCOPE(1), or UP, or SUB, or CALLER, or CALLER(0)
+       ...
+      }->();
+      # $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)
+     ...
+    }->();
+    # $cxt = SCOPE(4), UP SUB UP SUB, or UP SUB EVAL, or UP CALLER(2), or TOP
+    ...
+
+Where L</unwind> and L</want_at> point to depending on the C<$cxt>:
+
+    sub {
+     eval {
+      sub {
+       {
+        unwind @things => $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(3), or SUB UP SUB, or SUB EVAL, or CALLER(2)
+    ...
+

 =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'>.
 
 =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 constant L</SU_THREADSAFE> is also only exported on request, individually or by the tags C<':consts'> and C<':all'>.
+

 Same goes for the words L</TOP>, L</HERE>, L</UP>, L</SUB>, L</EVAL>, L</SCOPE> and L</CALLER> that are only exported on request, individually or by the tags C<':words'> and C<':all'>.
 
 =cut
 Same goes for the words L</TOP>, L</HERE>, L</UP>, L</SUB>, L</EVAL>, L</SCOPE> and L</CALLER> that are only exported on request, individually or by the tags C<':words'> and C<':all'>.
 
 =cut


@@ -250,8 +384,9 @@ use base qw/Exporter/;
 
 our @EXPORT      = ();
 our %EXPORT_TAGS = (
 
 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/ ],
+ funcs  => [ qw/reap localize localize_elem localize_delete unwind want_at/ ],
+ words  => [ qw/TOP HERE UP SUB EVAL SCOPE CALLER/ ],
+ consts => [ qw/SU_THREADSAFE/ ],

 );
 our @EXPORT_OK   = map { @$_ } values %EXPORT_TAGS;
 $EXPORT_TAGS{'all'} = [ @EXPORT_OK ];
 );
 our @EXPORT_OK   = map { @$_ } values %EXPORT_TAGS;
 $EXPORT_TAGS{'all'} = [ @EXPORT_OK ];


@@ -278,11 +413,12 @@ Consider those examples:
 
 The first case is "solved" by moving the C<local> before the C<reap>, and the second by using L</localize> instead of L</reap>.
 
 
 The first case is "solved" by moving the C<local> before the C<reap>, and the second by using L</localize> instead of L</reap>.
 

-L</reap>, L</localize> and L</localize_elem> effects can't cross C<BEGIN> blocks, hence calling those functions in C<import> is deemed to be useless.
+The effects of L</reap>, L</localize> and L</localize_elem> can't cross C<BEGIN> blocks, hence calling those functions in C<import> is deemed to be useless.

 This is an hopeless case because C<BEGIN> blocks are executed once while localizing constructs should do their job at each run.
 This is an hopeless case because C<BEGIN> blocks are executed once while localizing constructs should do their job at each run.

+However, it's possible to hook the end of the current scope compilation with L<B::Hooks::EndOfScope>.

 
 Some rare oddities may still happen when running inside the debugger.
 
 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 fixes.
+It may help to use a perl higher than 5.8.9 or 5.10.0, as they contain some context-related fixes.

 
 =head1 DEPENDENCIES
 
 
 =head1 DEPENDENCIES
 


@@ -290,8 +426,15 @@ L<XSLoader> (standard since perl 5.006).
 
 =head1 SEE ALSO
 
 
 =head1 SEE ALSO
 

+L<perlfunc/local>, L<perlsub/"Temporary Values via local()">.
+

 L<Alias>, L<Hook::Scope>, L<Scope::Guard>, L<Guard>.
 
 L<Alias>, L<Hook::Scope>, L<Scope::Guard>, L<Guard>.
 

+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>.
 =head1 AUTHOR
 
 Vincent Pit, C<< <perl at profvince.com> >>, L<http://www.profvince.com>.


@@ -300,7 +443,8 @@ You can contact me by mail or on C<irc.perl.org> (vincent).
 
 =head1 BUGS
 
 
 =head1 BUGS
 

-Please report any bugs or feature requests to C<bug-scope-upper at rt.cpan.org>, or through the web interface at L<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Scope-Upper>.  I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.
+Please report any bugs or feature requests to C<bug-scope-upper at rt.cpan.org>, or through the web interface at L<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Scope-Upper>.
+I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.

 
 =head1 SUPPORT
 
 
 =head1 SUPPORT
 


@@ -318,7 +462,7 @@ Thanks to Shawn M. Moore for motivation.
 
 =head1 COPYRIGHT & LICENSE
 
 
 =head1 COPYRIGHT & LICENSE
 

-Copyright 2008-2009 Vincent Pit, all rights reserved.
+Copyright 2008,2009,2010 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.
 
 
 This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.