File Coverage

blib/lib/PPIx/Regexp/Token/Assertion.pm

Criterion	Covered	Total	%
statement	45	47	95.7
branch	20	24	83.3
condition	10	14	71.4
subroutine	12	13	92.3
pod	3	3	100.0
total	90	101	89.1

=head1 NAME

PPIx::Regexp::Token::Assertion - Represent a simple assertion.

=head1 SYNOPSIS

 use PPIx::Regexp::Dumper;
 PPIx::Regexp::Dumper->new( 'qr{\bfoo\b}smx' )
     ->print();

=head1 INHERITANCE

C is a
L.

C has no descendants.

=head1 DESCRIPTION

This class represents one of the simple assertions; that is, those that
are not defined via parentheses. This includes the zero-width assertions
C<^>, C<$>, C<\b>, C<\B>, C<\A>, C<\Z>, C<\z> and C<\G>, as well as:

=over

=item * The C<\z> assertion added in Perl 5.005,

=item * The C<\K> assertion added in Perl 5.009005,

=item * The C<\b{gcb}> assertion (and friends) added in Perl 5.021009.
Similar braced constructions (like C<\b{foo}>) are unknown tokens.

=back

=head1 METHODS

This class provides no public methods beyond those provided by its
superclass.

=cut

package PPIx::Regexp::Token::Assertion;

use strict;
use warnings;

use base qw{ PPIx::Regexp::Token };

use PPIx::Regexp::Constant qw{
    COOKIE_CLASS
    COOKIE_LOOKAROUND_ASSERTION
    LITERAL_LEFT_CURLY_ALLOWED
    MINIMUM_PERL
    TOKEN_LITERAL
    TOKEN_UNKNOWN
    @CARP_NOT
};

use constant KEEP_EXPLANATION	=> 'In s///, keep everything before the \\K';

our $VERSION = '0.087';

# Return true if the token can be quantified, and false otherwise
# sub can_be_quantified { return };

my @braced_assertions = (
    [ qr< \\ [bB] [{] (?: g | gcb | wb | sb ) [}] >smx, '5.021009' ],
    [ qr< \\ [bB] [{] (?: lb ) [}] >smx, '5.023007' ],
    [ qr< \\ [bB] [{] .*? [}] >smx, undef, TOKEN_UNKNOWN,
	{ error => 'Unknown bound type' },
    ],
);

=head2 is_matcher

This method returns a true value because an assertion actually matches
something.

=cut

sub is_matcher { return 1; }

sub perl_version_introduced {
    my ( $self ) = @_;
    return ( $self->{perl_version_introduced} ||=
	$self->_perl_version_introduced() );
}

{

    my %perl_version_introduced = (
	'\\K' => '5.009005',
	'\\z' => '5.005',
    );

    sub _perl_version_introduced {
	my ( $self ) = @_;
	my $content = $self->content();
	foreach my $item ( @braced_assertions ) {
	    $content =~ m/ \A $item->[0] \z /smx
		and return $item->[1];
	}
	return $perl_version_introduced{ $content } || MINIMUM_PERL;
    }

}

sub perl_version_removed {
    my ( $self ) = @_;
    return ( $self->{perl_version_removed} ||=
	$self->_perl_version_removed() );
}

sub _perl_version_removed {
    my ( $self ) = @_;
    if ( '\\K' eq $self->content() ) {
	my $parent = $self;
	while ( $parent = $parent->parent() ) {
	    $parent->isa( 'PPIx::Regexp::Structure::Assertion' )
		and return '5.031003';
	}
    }
    return $self->SUPER::perl_version_removed();
}

{
    my %explanation = (
	'$'	=> 'Assert position is at end of string or newline',
	'\\A'	=> 'Assert position is at beginning of string',
	'\\B'	=> 'Assert position is not at word/nonword boundary',
	'\\B{gcb}'	=> 'Assert position is not at grapheme cluster boundary',
	'\\B{g}'	=> 'Assert position is not at grapheme cluster boundary',
	'\\B{lb}'	=> 'Assert position is not at line boundary',
	'\\B{sb}'	=> 'Assert position is not at sentence boundary',
	'\\B{wb}'	=> 'Assert position is not at word boundary',
	'\\G'	=> 'Assert position is at pos()',
	'\\K'	=> KEEP_EXPLANATION,
	'\\Z'	=> 'Assert position is at end of string, or newline before end',
	'\\b'	=> 'Assert position is at word/nonword boundary',
	'\\b{gcb}'	=> 'Assert position is at grapheme cluster boundary',
	'\\b{g}'	=> 'Assert position is at grapheme cluster boundary',
	'\\b{lb}'	=> 'Assert position is at line boundary',
	'\\b{sb}'	=> 'Assert position is at sentence boundary',
	'\\b{wb}'	=> 'Assert position is at word boundary',
	'\\z'	=> 'Assert position is at end of string',
	'^'	=> 'Assert position is at beginning of string or after newline',
    );

    sub __explanation {
	return \%explanation;
    }
}

# An un-escaped literal left curly bracket can always follow this
# element.
sub __following_literal_left_curly_disallowed_in {
    return LITERAL_LEFT_CURLY_ALLOWED;
}

# By logic we should handle '$' here. But
# PPIx::Regexp::Token::Interpolation needs to process it to see if it is
# a sigil. If it is not, that module is expected to make it into an
# assertion. This is to try to keep the order in which the tokenizers
# are called non-critical, and try to keep all processing for a
# character in one place. Except for the back slash, which gets in
# everywhere.
#
## my %assertion = map { $_ => 1 } qw{ ^ $ };
my %assertion = map { $_ => 1 } qw{ ^ };
my %escaped = map { $_ => 1 } qw{ b B A Z z G K };

sub __PPIX_TOKENIZER__regexp {
    my ( undef, $tokenizer, $character ) = @_;

    # Inside a character class, these are all literals.
    my $make = $tokenizer->cookie( COOKIE_CLASS ) ?
	TOKEN_LITERAL :
	__PACKAGE__;

    # '^' and '$'. Or at least '^'. See note above for '$'.
    $assertion{$character}
	and return $tokenizer->make_token( 1, $make );

    $character eq '\\' or return;

    defined ( my $next = $tokenizer->peek( 1 ) ) or return;

    # Handle assertions of the form \b{gcb} and friends, introduced in
    # Perl 5.21.9. These are not recognized inside square bracketed
    # character classes, where \b is not an assertion but a backspace
    # character.
    if ( __PACKAGE__ eq $make ) {	# Only outside [...]
	foreach my $item ( @braced_assertions ) {
	    my $end = $tokenizer->find_regexp( qr/ \A $item->[0] /smx )
		or next;
	    $item->[2]
		or return $end;
	    return $tokenizer->make_token( $end, $item->[2], $item->[3] );
	}
    }

    # We special-case '\K' because it was retracted inside look-around
    # assertions in 5.31.3.
    if ( 'K' eq $next && __PACKAGE__ eq $make &&
	$tokenizer->__cookie_exists( COOKIE_LOOKAROUND_ASSERTION ) ) {
	return $tokenizer->make_token( 2, $make, {
		perl_version_removed	=> '5.031003',
		explanation		=> KEEP_EXPLANATION .
		    '; retracted inside look-around assertion',
	    },
	);
    }

    $escaped{$next}
	and return $tokenizer->make_token( 2, $make );

    return;
}

1;

__END__