package Scope::Upper;
+use 5.006_001;
+
use strict;
use warnings;
=head1 VERSION
-Version 0.20
+Version 0.31
=cut
our $VERSION;
BEGIN {
- $VERSION = '0.20';
+ $VERSION = '0.31';
}
=head1 SYNOPSIS
=item *
-uniquely identify contextes with L</uid> and L</validate_uid>.
+uniquely identify contexts with L</uid> and L</validate_uid>.
=back
=item *
-A string beginning with C<'@'> or C<'%'>, for which the call is equivalent to respectiveley C<local $a[$key]; delete $a[$key]> and C<local $h{$key}; delete $h{$key}>.
+A string beginning with C<'@'> or C<'%'>, for which the call is equivalent to respectively C<local $a[$key]; delete $a[$key]> and C<local $h{$key}; delete $h{$key}>.
=item *
unwind;
unwind @values, $context;
-Returns C<@values> I<from> the subroutine, eval or format context pointed by or just above C<$context>, and immediately restart the program flow at this point - thus effectively returning C<@values> to an upper scope.
+Returns C<@values> I<from> the subroutine, eval or format context pointed by or just above C<$context>, and immediately restarts the program flow at this point - thus effectively returning C<@values> to an upper scope.
If C<@values> is empty, then the C<$context> parameter is optional and defaults to the current context (making the call equivalent to a bare C<return;>) ; otherwise it is mandatory.
The upper context isn't coerced onto C<@values>, which is hence always evaluated in list context.
yield;
yield @values, $context;
-Returns C<@values> I<from> the context pointed by or just above C<$context>, and immediately restart the program flow at this point.
+Returns C<@values> I<from> the context pointed by or just above C<$context>, and immediately restarts the program flow at this point.
If C<@values> is empty, then the C<$context> parameter is optional and defaults to the current context ; otherwise it is mandatory.
L</yield> differs from L</unwind> in that it can target I<any> upper scope (besides a C<s///e> substitution context) and not necessarily a sub, an eval or a format.
leave @values;
Immediately returns C<@values> from the current block, whatever it may be (besides a C<s///e> substitution context).
-C<leave> is actually a synonym for C<unwind HERE>, while C<leave @values> is a synonym for C<yield @values, HERE>.
+C<leave> is actually a synonym for C<yield HERE>, while C<leave @values> is a synonym for C<yield @values, HERE>.
Like for L</yield>, you can use the fifth value returned by L</context_info> to handle context coercion.
Gives information about the context denoted by C<$context>, akin to what L<perlfunc/caller> provides but not limited only to subroutine, eval and format contexts.
When C<$context> is omitted, it defaults to the current context.
-The values returned are, in order :
+The returned values are, in order :
=over 4
=head2 Getting a context from a context
For any of those functions, C<$from> is expected to be a context.
-When omitted, it defaults to the the current context.
+When omitted, it defaults to the current context.
=head3 C<UP>
my $upper_context = UP $from;
The context of the scope just above C<$from>.
+If C<$from> points to the top-level scope in the current stack, then a warning is emitted and C<$from> is returned (see L</DIAGNOSTICS> for details).
=head3 C<SUB>
my $sub_context = SUB $from;
The context of the closest subroutine above C<$from>.
-Note that C<$from> is returned if it is already a subroutine context ; hence C<SUB SUB == SUB>.
+If C<$from> already designates a subroutine context, then it is returned as-is ; hence C<SUB SUB == SUB>.
+If no subroutine context is present in the call stack, then a warning is emitted and the current context is returned (see L</DIAGNOSTICS> for details).
=head3 C<EVAL>
my $eval_context = EVAL $from;
The context of the closest eval above C<$from>.
-Note that C<$from> is returned if it is already an eval context ; hence C<EVAL EVAL == EVAL>.
+If C<$from> already designates an eval context, then it is returned as-is ; hence C<EVAL EVAL == EVAL>.
+If no eval context is present in the call stack, then a warning is emitted and the current context is returned (see L</DIAGNOSTICS> for details).
=head2 Getting a context from a level
my $context = SCOPE $level;
The C<$level>-th upper context, regardless of its type.
+If C<$level> points above the top-level scope in the current stack, then a warning is emitted and the top-level context is returned (see L</DIAGNOSTICS> for details).
=head3 C<CALLER>
The context of the C<$level>-th upper subroutine/eval/format.
It kind of corresponds to the context represented by C<caller $level>, but while e.g. C<caller 0> refers to the caller context, C<CALLER 0> will refer to the top scope in the current context.
+If C<$level> points above the top-level scope in the current stack, then a warning is emitted and the top-level context is returned (see L</DIAGNOSTICS> for details).
=head2 Examples
# (*) Note that uplevel() will croak if you pass that scope frame,
# because it cannot target eval scopes.
+=head1 DIAGNOSTICS
+
+=head2 C<Cannot target a scope outside of the current stack>
+
+This warning is emitted when L</UP>, L</SCOPE> or L</CALLER> end up pointing to a context that is above the top-level context of the current stack.
+It indicates that you tried to go higher than the main scope, or to point across a C<DESTROY> method, a signal handler, an overloaded or tied method call, a C<require> statement or a C<sort> callback.
+In this case, the resulting context is the highest reachable one.
+
+=head2 C<No targetable %s scope in the current stack>
+
+This warning is emitted when you ask for an L</EVAL> or L</SUB> context and no such scope can be found in the call stack.
+The resulting context is the current one.
+
=head1 EXPORT
The functions L</reap>, L</localize>, L</localize_elem>, L</localize_delete>, L</unwind>, L</yield>, L</leave>, L</want_at>, L</context_info> and L</uplevel> are only exported on request, either individually or by the tags C<':funcs'> and C<':all'>.
=head1 CAVEATS
+It is not possible to act upon a scope that belongs to another perl 'stack', i.e. to target a scope across a C<DESTROY> method, a signal handler, an overloaded or tied method call, a C<require> statement or a C<sort> callback.
+
Be careful that local variables are restored in the reverse order in which they were localized.
Consider those examples:
In those three 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.
+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 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>.
+Starting from C<perl> 5.19.4, it is unfortunately no longer possible to reliably throw exceptions from L</uplevel>'d code while the debugger is in use.
+This may be solved in a future version depending on how the core evolves.
+
=head1 DEPENDENCIES
-L<perl> 5.6.
+L<perl> 5.6.1.
A C compiler.
This module may happen to build with a C++ compiler as well, but don't rely on it, as no guarantee is made in this regard.
-L<XSLoader> (core since perl 5.006).
+L<XSLoader> (core since perl 5.6.0).
=head1 SEE ALSO
=head1 AUTHOR
-Vincent Pit, C<< <perl at profvince.com> >>, L<http://www.profvince.com>.
+Vincent Pit C<< <vpit at cpan.org> >>.
You can contact me by mail or on C<irc.perl.org> (vincent).
perldoc Scope::Upper
-Tests code coverage report is available at L<http://www.profvince.com/perl/cover/Scope-Upper>.
-
=head1 ACKNOWLEDGEMENTS
Inspired by Ricardo Signes.
+The reimplementation of a large part of this module for perl 5.24 was provided by David Mitchell.
+His work was sponsored by the Perl 5 Core Maintenance Grant from The Perl Foundation.
+
Thanks to Shawn M. Moore for motivation.
=head1 COPYRIGHT & LICENSE
-Copyright 2008,2009,2010,2011,2012 Vincent Pit, all rights reserved.
+Copyright 2008,2009,2010,2011,2012,2013,2014,2015,2016,2017,2018,2019 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.
projects / perl / modules / Scope-Upper.git / blobdiff