X-Git-Url: http://git.vpit.fr/?a=blobdiff_plain;f=lib%2FScope%2FUpper.pm;h=acd566b0f7588a166d2cf460f3e7f1f76f33492b;hb=d965a45a64e2aab24e3adbda18543e80a0b81e57;hp=988254fa5016b804443464a1fbb23fb2067aa5d9;hpb=9a258ccdcca73cc6ca9470c06e7db103c3ba8193;p=perl%2Fmodules%2FScope-Upper.git

diff --git a/lib/Scope/Upper.pm b/lib/Scope/Upper.pm
index 988254f..acd566b 100644
--- a/lib/Scope/Upper.pm
+++ b/lib/Scope/Upper.pm
@@ -9,61 +9,89 @@ Scope::Upper - Act on upper scopes.
 
 =head1 VERSION
 
-Version 0.05
+Version 0.13
 
 =cut
 
 our $VERSION;
 BEGIN {
- $VERSION = '0.05';
+ $VERSION = '0.13';
 }
 
 =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/;
 
-    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 {
-      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->();
-     my $cx = SUB UP SUB;
+     my $cx = SUB UP; # Point to the sub above this one
      unwind +(want_at($cx) ? @result : scalar @result) => $cx;
     }
 
@@ -71,28 +99,44 @@ 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
 
 =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.
 
-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.
-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
 
@@ -103,11 +147,11 @@ BEGIN {
 
 =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>
 
-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
@@ -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.
 
-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>
 
-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.
 
+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
@@ -169,7 +233,7 @@ 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>.
+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
@@ -177,6 +241,7 @@ This means that
     my $num = sub {
      my @a = ('a' .. 'z');
      unwind @a => HERE;
+     # not reached
     }->();
 
 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>
 
-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;
+     # 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
 
@@ -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<$from>.
+Note that C<$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<$from>.
+Note that C<$from> is returned if it is already an eval context ; hence C<EVAL EVAL == EVAL>.
 
 =head2 Getting a context from a level
 
@@ -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.
 
+=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'>.
 
+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
@@ -250,8 +384,9 @@ 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/ ],
+ 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 ];
@@ -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>.
 
-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.
+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.
-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
 
@@ -290,8 +426,15 @@ 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<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>.
@@ -300,7 +443,8 @@ You can contact me by mail or on C<irc.perl.org> (vincent).
 
 =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
 
@@ -318,7 +462,7 @@ Thanks to Shawn M. Moore for motivation.
 
 =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.