package feature;
-our $VERSION = '1.63';
+our $VERSION = '1.69';
our %feature = (
fc => 'feature_fc',
isa => 'feature_isa',
say => 'feature_say',
try => 'feature_try',
+ defer => 'feature_defer',
state => 'feature_state',
switch => 'feature_switch',
bitwise => 'feature_bitwise',
"5.15" => [qw(bareword_filehandles current_sub evalbytes fc indirect multidimensional say state switch unicode_eval unicode_strings)],
"5.23" => [qw(bareword_filehandles current_sub evalbytes fc indirect multidimensional postderef_qq say state switch unicode_eval unicode_strings)],
"5.27" => [qw(bareword_filehandles bitwise current_sub evalbytes fc indirect multidimensional postderef_qq say state switch unicode_eval unicode_strings)],
- "all" => [qw(bareword_filehandles bitwise current_sub declared_refs evalbytes fc indirect isa multidimensional postderef_qq refaliasing say signatures state switch try unicode_eval unicode_strings)],
+ "5.35" => [qw(bitwise current_sub evalbytes fc postderef_qq say state unicode_eval unicode_strings)],
+ "all" => [qw(bareword_filehandles bitwise current_sub declared_refs defer evalbytes fc indirect isa multidimensional postderef_qq refaliasing say signatures state switch try unicode_eval unicode_strings)],
"default" => [qw(bareword_filehandles indirect multidimensional)],
);
$feature_bundle{"5.32"} = $feature_bundle{"5.27"};
$feature_bundle{"5.33"} = $feature_bundle{"5.27"};
$feature_bundle{"5.34"} = $feature_bundle{"5.27"};
+$feature_bundle{"5.36"} = $feature_bundle{"5.35"};
$feature_bundle{"5.9.5"} = $feature_bundle{"5.10"};
my %noops = (
postderef => 1,
our $hint_shift = 26;
our $hint_mask = 0x3c000000;
-our @hint_bundles = qw( default 5.10 5.11 5.15 5.23 5.27 );
+our @hint_bundles = qw( default 5.10 5.11 5.15 5.23 5.27 5.35 );
# This gets set (for now) in $^H as well as in %^H,
# for runtime speed of the uc/lc/ucfirst/lcfirst functions.
=head1 SYNOPSIS
- use feature qw(say switch);
- given ($foo) {
- when (1) { say "\$foo == 1" }
- when ([2,3]) { say "\$foo == 2 || \$foo == 3" }
- when (/^a[bc]d$/) { say "\$foo eq 'abd' || \$foo eq 'acd'" }
- when ($_ > 100) { say "\$foo > 100" }
- default { say "None of the above" }
- }
+ use feature qw(fc say);
+
+ # Without the "use feature" above, this code would not be able to find
+ # the built-ins "say" or "fc":
+ say "The case-folded version of $x is: " . fc $x;
+
+
+ # set features to match the :5.10 bundle, which may turn off or on
+ # multiple features (see below)
+ use feature ':5.10';
- use feature ':5.10'; # loads all features available in perl 5.10
- use v5.10; # implicitly loads :5.10 feature bundle
+ # implicitly loads :5.10 feature bundle
+ use v5.10;
=head1 DESCRIPTION
=head2 The 'switch' feature
-B<WARNING>: Because the L<smartmatch operator|perlop/"Smartmatch Operator"> is
-experimental, Perl will warn when you use this feature, unless you have
-explicitly disabled the warning:
+B<WARNING>: This feature is still experimental and the implementation may
+change or be removed in future versions of Perl. For this reason, Perl will
+warn when you use the feature, unless you have explicitly disabled the warning:
no warnings "experimental::smartmatch";
them, so the feature can be enabled and disabled. Details are at
L<perlfunc/Under the "unicode_eval" feature>.
-C<evalbytes> is like string C<eval>, but operating on a byte stream that is
-
not UTF-8 encoded. Details are at L<perlfunc/evalbytes EXPR>. Without a
+C<evalbytes> is like string C<eval>, but it treats its argument as a byte
+
string. Details are at L<perlfunc/evalbytes EXPR>. Without a
S<C<use feature 'evalbytes'>> nor a S<C<use v5.16>> (or higher) declaration in
the current scope, you can still access it by instead writing
C<CORE::evalbytes>.
=head2 The 'signatures' feature
B<WARNING>: This feature is still experimental and the implementation may
-change in future versions of Perl. For this reason, Perl will
-warn when you use the feature, unless you have explicitly disabled the
-warning:
+change or be removed in future versions of Perl. For this reason, Perl will
+warn when you use the feature, unless you have explicitly disabled the warning:
no warnings "experimental::signatures";
=head2 The 'refaliasing' feature
B<WARNING>: This feature is still experimental and the implementation may
-change in future versions of Perl. For this reason, Perl will
-warn when you use the feature, unless you have explicitly disabled the
-warning:
+change or be removed in future versions of Perl. For this reason, Perl will
+warn when you use the feature, unless you have explicitly disabled the warning:
no warnings "experimental::refaliasing";
=head2 The 'declared_refs' feature
B<WARNING>: This feature is still experimental and the implementation may
-change in future versions of Perl. For this reason, Perl will
-warn when you use the feature, unless you have explicitly disabled the
-warning:
+change or be removed in future versions of Perl. For this reason, Perl will
+warn when you use the feature, unless you have explicitly disabled the warning:
no warnings "experimental::declared_refs";
scalar given by the left operand is an object of the class given by the
right operand. See L<perlop/Class Instance Operator> for more details.
-This feature is available from Perl 5.32 onwards.
+This feature is available from Perl 5.32 onwards. From Perl 5.32 to 5.34,
+it was classed as experimental, and Perl emitted a warning for its usage,
+except when explicitly disabled:
+
+ no warnings "experimental::isa";
+
+As of Perl 5.36, use of this feature no longer triggers a warning (though the
+C<experimental::isa> warning category stilll exists for compatibility with
+code that disables it).
=head2 The 'indirect' feature
This feature enables multidimensional array emulation, a perl 4 (or
earlier) feature that was used to emulate multidimensional arrays with
-hashes. This works by converting code like C<< $foo{$x, y} >> into
-C<< $foo{join($;, $x, $y} >>. It is enabled by default, but can be
+hashes. This works by converting code like C<< $foo{$x, $y} >> into
+C<< $foo{join($;, $x, $y)} >>. It is enabled by default, but can be
turned off to disable multidimensional array emulation.
When this feature is disabled the syntax that is normally replaced
The perl built-in filehandles C<STDIN>, C<STDOUT>, C<STDERR>, C<DATA>,
C<ARGV>, C<ARGVOUT> and the special C<_> are always enabled.
-This feature is enabled under this name from Perl 5.34 onwards. In
-previous versions it was simply on all the time.
+This behavior was always present in versions before Perl 5.34. In Perl 5.34,
+it was made controllable with the C<feature> pragma, but was on by default.
+It is not present in the C<:5.36> feature bundle, so C<use v5.36> disables
+this feature.
You can use the L<bareword::filehandles> module on CPAN to disable
bareword filehandles for older versions of perl.
=head2 The 'try' feature.
+B<WARNING>: This feature is still experimental and the implementation may
+change or be removed in future versions of Perl. For this reason, Perl will
+warn when you use the feature, unless you have explicitly disabled the warning:
+
+ no warnings "experimental::try";
+
This feature enables the C<try> and C<catch> syntax, which allows exception
-handling, where exceptions throwin from the body of the block introduced with
+handling, where exceptions thrown from the body of the block introduced with
C<try> are caught by executing the body of the C<catch> block.
For more information, see L<perlsyn/"Try Catch Exception Handling">.
+=head2 The 'defer' feature
+
+This feature enables the C<defer> block syntax, which allows a block of code
+to be deferred until when the flow of control leaves the block which contained
+it. For more details, see L<perlsyn/defer>.
+
=head1 FEATURE BUNDLES
It's possible to load multiple features together, using
postderef_qq say state switch unicode_eval
unicode_strings
+ :5.36 bitwise current_sub evalbytes fc
+ postderef_qq say state unicode_eval
+ unicode_strings
+
The C<:default> bundle represents the feature set that is enabled before
any C<use feature> or C<no feature> declaration.
=back
+=head1 CHECKING FEATURES
+
+C<feature> provides some simple APIs to check which features are enabled.
+
+These functions cannot be imported and must be called by their fully
+qualified names. If you don't otherwise need to set a feature you will
+need to ensure C<feature> is loaded with:
+
+ use feature ();
+
+=over
+
+=item feature_enabled($feature)
+
+=item feature_enabled($feature, $depth)
+
+ package MyStandardEnforcer;
+ use feature ();
+ use Carp "croak";
+ sub import {
+ croak "disable indirect!" if feature::feature_enabled("indirect");
+ }
+
+Test whether a named feature is enabled at a given level in the call
+stack, returning a true value if it is. C<$depth> defaults to 1,
+which checks the scope that called the scope calling
+feature::feature_enabled().
+
+croaks for an unknown feature name.
+
+=item features_enabled()
+
+=item features_enabled($depth)
+
+ package ReportEnabledFeatures;
+ use feature "say";
+ sub import {
+ say STDERR join " ", feature::features_enabled();
+ }
+
+Returns a list of the features enabled at a given level in the call
+stack. C<$depth> defaults to 1, which checks the scope that called
+the scope calling feature::features_enabled().
+
+=item feature_bundle()
+
+=item feature_bundle($depth)
+
+Returns the feature bundle, if any, selected at a given level in the
+call stack. C<$depth> defaults to 1, which checks the scope that called
+the scope calling feature::feature_bundle().
+
+Returns an undefined value if no feature bundle is selected in the
+scope.
+
+The bundle name returned will be for the earliest bundle matching the
+selected bundle, so:
+
+ use feature ();
+ use v5.12;
+ BEGIN { print feature::feature_bundle(0); }
+
+will print C<5.11>.
+
+This returns internal state, at this point C<use v5.12;> sets the
+feature bundle, but C< use feature ":5.12"; > does not set the feature
+bundle. This may change in a future release of perl.
+
+=back
+
=cut
sub import {
Carp::croak(@_);
}
+sub features_enabled {
+ my ($depth) = @_;
+
+ $depth //= 1;
+ my @frame = caller($depth+1)
+ or return;
+ my ($hints, $hinthash) = @frame[8, 10];
+
+ my $bundle_number = $hints & $hint_mask;
+ if ($bundle_number != $hint_mask) {
+ return $feature_bundle{$hint_bundles[$bundle_number >> $hint_shift]}->@*;
+ }
+ else {
+ my @features;
+ for my $feature (sort keys %feature) {
+ if ($hinthash->{$feature{$feature}}) {
+ push @features, $feature;
+ }
+ }
+ return @features;
+ }
+}
+
+sub feature_enabled {
+ my ($feature, $depth) = @_;
+
+ $depth //= 1;
+ my @frame = caller($depth+1)
+ or return;
+ my ($hints, $hinthash) = @frame[8, 10];
+
+ my $hint_feature = $feature{$feature}
+ or croak "Unknown feature $feature";
+ my $bundle_number = $hints & $hint_mask;
+ if ($bundle_number != $hint_mask) {
+ my $bundle = $hint_bundles[$bundle_number >> $hint_shift];
+ for my $bundle_feature ($feature_bundle{$bundle}->@*) {
+ return 1 if $bundle_feature eq $feature;
+ }
+ return 0;
+ }
+ else {
+ return $hinthash->{$hint_feature} // 0;
+ }
+}
+
+sub feature_bundle {
+ my $depth = shift;
+
+ $depth //= 1;
+ my @frame = caller($depth+1)
+ or return;
+ my $bundle_number = $frame[8] & $hint_mask;
+ if ($bundle_number != $hint_mask) {
+ return $hint_bundles[$bundle_number >> $hint_shift];
+ }
+ else {
+ return undef;
+ }
+}
+
1;
# ex: set ro:
https://perl5.git.perl.org / perl5.git / blobdiff