package B::Lint;
use if $] > 5.017, 'deprecate';

our $VERSION = '1.17'; ## no critic

=head1 NAME

B::Lint - Perl lint

=head1 SYNOPSIS

perl -MO=Lint[,OPTIONS] foo.pl

=head1 DESCRIPTION

The B::Lint module is equivalent to an extended version of the B<-w>
option of B<perl>. It is named after the program F<lint> which carries
out a similar process for C programs.

=head1 OPTIONS AND LINT CHECKS

Option words are separated by commas (not whitespace) and follow the
usual conventions of compiler backend options. Following any options
(indicated by a leading B<->) come lint check arguments. Each such
argument (apart from the special B<all> and B<none> options) is a
word representing one possible lint check (turning on that check) or
is B<no-foo> (turning off that check). Before processing the check
arguments, a standard list of checks is turned on. Later options
override earlier ones. Available options are:

=over 8

=item B<magic-diamond>

Produces a warning whenever the magic C<E<lt>E<gt>> readline is
used. Internally it uses perl's two-argument open which itself treats
filenames with special characters specially. This could allow
interestingly named files to have unexpected effects when reading.

% touch 'rm *|'
% perl -pe 1

The above creates a file named C<rm *|>. When perl opens it with
C<E<lt>E<gt>> it actually executes the shell program C<rm *>. This
makes C<E<lt>E<gt>> dangerous to use carelessly.

=item B<context>

Produces a warning whenever an array is used in an implicit scalar
context. For example, both of the lines

$foo = length(@bar);
$foo = @bar;

will elicit a warning. Using an explicit B<scalar()> silences the
warning. For example,

$foo = scalar(@bar);

=item B<implicit-read> and B<implicit-write>

These options produce a warning whenever an operation implicitly
reads or (respectively) writes to one of Perl's special variables.
For example, B<implicit-read> will warn about these:

/foo/;

and B<implicit-write> will warn about these:

s/foo/bar/;

Both B<implicit-read> and B<implicit-write> warn about this:

for (@a) { ... }

=item B<bare-subs>

This option warns whenever a bareword is implicitly quoted, but is also
the name of a subroutine in the current package. Typical mistakes that it will
trap are:

use constant foo => 'bar';
@a = ( foo => 1 );
$b{foo} = 2;

Neither of these will do what a naive user would expect.

=item B<dollar-underscore>

This option warns whenever C<$_> is used either explicitly anywhere or
as the implicit argument of a B<print> statement.

=item B<private-names>

This option warns on each use of any variable, subroutine or
method name that lives in a non-current package but begins with
an underscore ("_"). Warnings aren't issued for the special case
of the single character name "_" by itself (e.g. C<$_> and C<@_>).

=item B<undefined-subs>

This option warns whenever an undefined subroutine is invoked.
This option will only catch explicitly invoked subroutines such
as C<foo()> and not indirect invocations such as C<&$subref()>
or C<$obj-E<gt>meth()>. Note that some programs or modules delay
definition of subs until runtime by means of the AUTOLOAD
mechanism.

=item B<regexp-variables>

This option warns whenever one of the regexp variables C<$`>, C<$&> or C<$'>
is used. Any occurrence of any of these variables in your
program can slow your whole program down. See L<perlre> for
details.

=item B<all>

Turn all warnings on.

=item B<none>

Turn all warnings off.

=back

=head1 NON LINT-CHECK OPTIONS

=over 8

=item B<-u Package>

Normally, Lint only checks the main code of the program together
with all subs defined in package main. The B<-u> option lets you
include other package names whose subs are then checked by Lint.

=back

=head1 EXTENDING LINT

Lint can be extended by with plugins. Lint uses L<Module::Pluggable>
to find available plugins. Plugins are expected but not required to
inform Lint of which checks they are adding.

The C<< B::Lint->register_plugin( MyPlugin => \@new_checks ) >> method
adds the list of C<@new_checks> to the list of valid checks. If your
module wasn't loaded by L<Module::Pluggable> then your class name is
added to the list of plugins.

You must create a C<match( \%checks )> method in your plugin class or one
of its parents. It will be called on every op as a regular method call
with a hash ref of checks as its parameter.

The class methods C<< B::Lint->file >> and C<< B::Lint->line >> contain
the current filename and line number.

package Sample;
use B::Lint;
B::Lint->register_plugin( Sample => [ 'good_taste' ] );

sub match {
my ( $op, $checks_href ) = shift @_;
if ( $checks_href->{good_taste} ) {
...
}
}

=head1 TODO

=over

=item while(<FH>) stomps $_

=item strict oo

=item unchecked system calls

=item more tests, validate against older perls

=back

=head1 BUGS

This is only a very preliminary version.

=head1 AUTHOR

Malcolm Beattie, [email protected].

=head1 ACKNOWLEDGEMENTS

Sebastien Aperghis-Tramoni - bug fixes

=cut

use strict;
use B qw( walkoptree_slow
main_root main_cv walksymtable parents
OPpOUR_INTRO
OPf_WANT_VOID OPf_WANT_LIST OPf_WANT OPf_STACKED SVf_POK );
use Carp 'carp';

# The current M::P doesn't know about .pmc files.
use Module::Pluggable ( require => 1 );

use List::Util 'first';
## no critic Prototypes
sub any (&@) { my $test = shift @_; $test->() and return 1 for @_; return 0 }

BEGIN {

# Import or create some constants from B. B doesn't provide
# everything I need so some things like OPpCONST_BARE are defined
# here.
for my $sym ( qw( begin_av check_av init_av end_av ),
[ 'OPpCONST_BARE' => 64 ] )
{
my $val;
( $sym, $val ) = @$sym if ref $sym;

if ( any { $sym eq $_ } @B::EXPORT_OK, @B::EXPORT ) {
B->import($sym);
}
else {
require constant;
constant->import( $sym => $val );
}
}
}

my $file = "unknown"; # shadows current filename
my $line = 0; # shadows current line number
my $curstash = "main"; # shadows current stash
my $curcv; # shadows current B::CV for pad lookups

sub file {$file}
sub line {$line}
sub curstash {$curstash}
sub curcv {$curcv}

# Lint checks
my %check;
my %implies_ok_context;

map( $implies_ok_context{$_}++,
qw(scalar av2arylen aelem aslice helem hslice
keys values hslice defined undef delete) );

# Lint checks turned on by default
my @default_checks
= qw(context magic_diamond undefined_subs regexp_variables);

my %valid_check;

# All valid checks
for my $check (
qw(context implicit_read implicit_write dollar_underscore
private_names bare_subs undefined_subs regexp_variables
magic_diamond )
)
{
$valid_check{$check} = __PACKAGE__;
}

# Debugging options
my ($debug_op);

my %done_cv; # used to mark which subs have already been linted
my @extra_packages; # Lint checks mainline code and all subs which are
# in main:: or in one of these packages.

sub warning {
my $format = ( @_ < 2 ) ? "%s" : shift @_;
warn sprintf( "$format at %s line %d\n", @_, $file, $line );
return undef; ## no critic undef
}

# This gimme can't cope with context that's only determined
# at runtime via dowantarray().
sub gimme {
my $op = shift @_;
my $flags = $op->flags;
if ( $flags & OPf_WANT ) {
return ( ( $flags & OPf_WANT ) == OPf_WANT_LIST ? 1 : 0 );
}
return undef; ## no critic undef
}

my @plugins = __PACKAGE__->plugins;

sub inside_grepmap {

# A boolean function to be used while inside a B::walkoptree_slow
# call. If we are in the EXPR part of C<grep EXPR, ...> or C<grep
# { EXPR } ...>, this returns true.
return any { $_->name =~ m/\A(?:grep|map)/xms } @{ parents() };
}

sub inside_foreach_modifier {

# TODO: use any()

# A boolean function to be used while inside a B::walkoptree_slow
# call. If we are in the EXPR part of C<EXPR foreach ...> this
# returns true.
for my $ancestor ( @{ parents() } ) {
next unless $ancestor->name eq 'leaveloop';

my $first = $ancestor->first;
next unless $first->name eq 'enteriter';

next if $first->redoop->name =~ m/\A(?:next|db|set)state\z/xms;

return 1;
}
return 0;
}

for (
[qw[ B::PADOP::gv_harder gv padix]],
[qw[ B::SVOP::sv_harder sv targ]],
[qw[ B::SVOP::gv_harder gv padix]]
)
{

# I'm generating some functions here because they're mostly
# similar. It's all for compatibility with threaded
# perl. Perhaps... this code should inspect $Config{usethreads}
# and generate a *specific* function. I'm leaving it generic for
# the moment.
#
# In threaded perl SVs and GVs aren't used directly in the optrees
# like they are in non-threaded perls. The ops that would use a SV
# or GV keep an index into the subroutine's scratchpad. I'm
# currently ignoring $cv->DEPTH and that might be at my peril.

my ( $subname, $attr, $pad_attr ) = @$_;
my $target = do { ## no critic strict
no strict 'refs';
\*$subname;
};
*$target = sub {
my ($op) = @_;

my $elt;
if ( not $op->isa('B::PADOP') ) {
$elt = $op->$attr;
}
return $elt if eval { $elt->isa('B::SV') };

my $ix = $op->$pad_attr;
my @entire_pad = $curcv->PADLIST->ARRAY;
my @elts = map +( $_->ARRAY )[$ix], @entire_pad;
($elt) = first {
eval { $_->isa('B::SV') } ? $_ : ();
}
@elts[ 0, reverse 1 .. $#elts ];
return $elt;
};
}

sub B::OP::lint {
my ($op) = @_;

# This is a fallback ->lint for all the ops where I haven't
# defined something more specific. Nothing happens here.

# Call all registered plugins
my $m;
$m = $_->can('match'), $op->$m( \%check ) for @plugins;
return;
}

sub B::COP::lint {
my ($op) = @_;

# nextstate ops sit between statements. Whenever I see one I
# update the current info on file, line, and stash. This code also
# updates it when it sees a dbstate or setstate op. I have no idea
# what those are but having seen them mentioned together in other
# parts of the perl I think they're kind of equivalent.
if ( $op->name =~ m/\A(?:next|db|set)state\z/ ) {
$file = $op->file;
$line = $op->line;
$curstash = $op->stash->NAME;
}

# Call all registered plugins
my $m;
$m = $_->can('match'), $op->$m( \%check ) for @plugins;
return;
}

sub B::UNOP::lint {
my ($op) = @_;

my $opname = $op->name;

CONTEXT: {

# Check arrays and hashes in scalar or void context where
# scalar() hasn't been used.

next
unless $check{context}
and $opname =~ m/\Arv2[ah]v\z/xms
and not gimme($op);

my ( $parent, $gparent ) = @{ parents() }[ 0, 1 ];
my $pname = $parent->name;

next if $implies_ok_context{$pname};

# Three special cases to deal with: "foreach (@foo)", "delete
# $a{$b}", and "exists $a{$b}" null out the parent so we have to
# check for a parent of pp_null and a grandparent of
# pp_enteriter, pp_delete, pp_exists

next
if $pname eq "null"
and $gparent->name =~ m/\A(?:delete|enteriter|exists)\z/xms;

# our( @bar ); would also trigger this error so I exclude
# that.
next
if $op->private & OPpOUR_INTRO
and ( $op->flags & OPf_WANT ) == OPf_WANT_VOID;

warning 'Implicit scalar context for %s in %s',
$opname eq "rv2av" ? "array" : "hash", $parent->desc;
}

PRIVATE_NAMES: {

# Looks for calls to methods with names that begin with _ and
# that aren't visible within the current package. Maybe this
# should look at @ISA.
next
unless $check{private_names}
and $opname =~ m/\Amethod/xms;

my $methop = $op->first;
next unless $methop->name eq "const";

my $method = $methop->sv_harder->PV;
next
unless $method =~ m/\A_/xms
and not defined &{"$curstash\::$method"};

warning q[Illegal reference to private method name '%s'], $method;
}

# Call all registered plugins
my $m;
$m = $_->can('match'), $op->$m( \%check ) for @plugins;
return;
}

sub B::PMOP::lint {
my ($op) = @_;

IMPLICIT_READ: {

# Look for /.../ that doesn't use =~ to bind to something.
next
unless $check{implicit_read}
and $op->name eq "match"
and not( $op->flags & OPf_STACKED
or inside_grepmap() );
warning 'Implicit match on $_';
}

IMPLICIT_WRITE: {

# Look for s/.../.../ that doesn't use =~ to bind to
# something.
next
unless $check{implicit_write}
and $op->name eq "subst"
and not $op->flags & OPf_STACKED;
warning 'Implicit substitution on $_';
}

# Call all registered plugins
my $m;
$m = $_->can('match'), $op->$m( \%check ) for @plugins;
return;
}

sub B::LOOP::lint {
my ($op) = @_;

IMPLICIT_FOO: {

# Look for C<for ( ... )>.
next
unless ( $check{implicit_read} or $check{implicit_write} )
and $op->name eq "enteriter";

my $last = $op->last;
next
unless $last->name eq "gv"
and $last->gv_harder->NAME eq "_"
and $op->redoop->name =~ m/\A(?:next|db|set)state\z/xms;

warning 'Implicit use of $_ in foreach';
}

# Call all registered plugins
my $m;
$m = $_->can('match'), $op->$m( \%check ) for @plugins;
return;
}

# In threaded vs non-threaded perls you'll find that threaded perls
# use PADOP in place of SVOPs so they can do lookups into the
# scratchpad to find things. I suppose this is so a optree can be
# shared between threads and all symbol table muckery will just get
# written to a scratchpad.
*B::PADOP::lint = *B::PADOP::lint = \&B::SVOP::lint;

sub B::SVOP::lint {
my ($op) = @_;

MAGIC_DIAMOND: {
next
unless $check{magic_diamond}
and parents()->[0]->name eq 'readline'
and $op->gv_harder->NAME eq 'ARGV';

warning 'Use of <>';
}

BARE_SUBS: {
next
unless $check{bare_subs}
and $op->name eq 'const'
and $op->private & OPpCONST_BARE;

my $sv = $op->sv_harder;
next unless $sv->FLAGS & SVf_POK;

my $sub = $sv->PV;
my $subname = "$curstash\::$sub";

# I want to skip over things that were declared with the
# constant pragma. Well... sometimes. Hmm. I want to ignore
# C<<use constant FOO => ...>> but warn on C<<FOO => ...>>
# later. The former is typical declaration syntax and the
# latter would be an error.
#
# Skipping over both could be handled by looking if
# $constant::declared{$subname} is true.

# Check that it's a function.
next
unless exists &{"$curstash\::$sub"};

warning q[Bare sub name '%s' interpreted as string], $sub;
}

PRIVATE_NAMES: {
next unless $check{private_names};

my $opname = $op->name;
if ( $opname =~ m/\Agv(?:sv)?\z/xms ) {

# Looks for uses of variables and stuff that are named
# private and we're not in the same package.
my $gv = $op->gv_harder;
my $name = $gv->NAME;
next
unless $name =~ m/\A_./xms
and $gv->STASH->NAME ne $curstash;

warning q[Illegal reference to private name '%s'], $name;
}
elsif ( $opname eq "method_named" ) {
my $method = $op->sv_harder->PV;
next unless $method =~ m/\A_./xms;

warning q[Illegal reference to private method name '%s'], $method;
}
}

DOLLAR_UNDERSCORE: {

# Warn on uses of $_ with a few exceptions. I'm not warning on
# $_ inside grep, map, or statement modifier foreach because
# they localize $_ and it'd be impossible to use these
# features without getting warnings.

next
unless $check{dollar_underscore}
and $op->name eq "gvsv"
and $op->gv_harder->NAME eq "_"
and not( inside_grepmap
or inside_foreach_modifier );

warning 'Use of $_';
}

REGEXP_VARIABLES: {

# Look for any uses of $`, $&, or $'.
next
unless $check{regexp_variables}
and $op->name eq "gvsv";

my $name = $op->gv_harder->NAME;
next unless $name =~ m/\A[\&\'\`]\z/xms;

warning 'Use of regexp variable $%s', $name;
}

UNDEFINED_SUBS: {

# Look for calls to functions that either don't exist or don't
# have a definition.
next
unless $check{undefined_subs}
and $op->name eq "gv"
and $op->next->name eq "entersub";

my $gv = $op->gv_harder;
my $subname = $gv->STASH->NAME . "::" . $gv->NAME;

no strict 'refs'; ## no critic strict
if ( not exists &$subname ) {
$subname =~ s/\Amain:://;
warning q[Nonexistent subroutine '%s' called], $subname;
}
elsif ( not defined &$subname ) {
$subname =~ s/\A\&?main:://;
warning q[Undefined subroutine '%s' called], $subname;
}
}

# Call all registered plugins
my $m;
$m = $_->can('match'), $op->$m( \%check ) for @plugins;
return;
}

sub B::GV::lintcv {

# Example: B::svref_2object( \ *A::Glob )->lintcv

my $gv = shift @_;
my $cv = $gv->CV;
return unless $cv->can('lintcv');
$cv->lintcv;
return;
}

sub B::CV::lintcv {

# Example: B::svref_2object( \ &foo )->lintcv

# Write to the *global* $
$curcv = shift @_;

#warn sprintf("lintcv: %s::%s (done=%d)\n",
# $gv->STASH->NAME, $gv->NAME, $done_cv{$$curcv});#debug
return unless ref($curcv) and $$curcv and not $done_cv{$$curcv}++;
my $root = $curcv->ROOT;

#warn " root = $root (0x$$root)\n";#debug
walkoptree_slow( $root, "lint" ) if $$root;
return;
}

sub do_lint {
my %search_pack;

# Copy to the global $curcv for use in pad lookups.
$curcv = main_cv;
walkoptree_slow( main_root, "lint" ) if ${ main_root() };

# Do all the miscellaneous non-sub blocks.
for my $av ( begin_av, init_av, check_av, end_av ) {
next unless eval { $av->isa('B::AV') };
for my $cv ( $av->ARRAY ) {
next unless ref($cv) and $cv->FILE eq $0;
$cv->lintcv;
}
}

walksymtable(
\%main::,
sub {
if ( $_[0]->FILE eq $0 ) { $_[0]->lintcv }
},
sub {1}
);
return;
}

sub compile {
my @options = @_;

# Turn on default lint checks
for my $opt (@default_checks) {
$check{$opt} = 1;
}

OPTION:
while ( my $option = shift @options ) {
my ( $opt, $arg );
unless ( ( $opt, $arg ) = $option =~ m/\A-(.)(.*)/xms ) {
unshift @options, $option;
last OPTION;
}

if ( $opt eq "-" && $arg eq "-" ) {
shift @options;
last OPTION;
}
elsif ( $opt eq "D" ) {
$arg ||= shift @options;
foreach my $arg ( split //, $arg ) {
if ( $arg eq "o" ) {
B->debug(1);
}
elsif ( $arg eq "O" ) {
$debug_op = 1;
}
}
}
elsif ( $opt eq "u" ) {
$arg ||= shift @options;
push @extra_packages, $arg;
}
}

foreach my $opt ( @default_checks, @options ) {
$opt =~ tr/-/_/;
if ( $opt eq "all" ) {
%check = %valid_check;
}
elsif ( $opt eq "none" ) {
%check = ();
}
else {
if ( $opt =~ s/\Ano_//xms ) {
$check{$opt} = 0;
}
else {
$check{$opt} = 1;
}
carp "No such check: $opt"
unless defined $valid_check{$opt};
}
}

# Remaining arguments are things to check. So why aren't I
# capturing them or something? I don't know.

return \&do_lint;
}

sub register_plugin {
my ( undef, $plugin, $new_checks ) = @_;

# Allow the user to be lazy and not give us a name.
$plugin = caller unless defined $plugin;

# Register the plugin's named checks, if any.
for my $check ( eval {@$new_checks} ) {
if ( not defined $check ) {
carp 'Undefined value in checks.';
next;
}
if ( exists $valid_check{$check} ) {
carp
"$check is already registered as a $valid_check{$check} feature.";
next;
}

$valid_check{$check} = $plugin;
}

# Register a non-Module::Pluggable loaded module. @plugins already
# contains whatever M::P found on disk. The user might load a
# plugin manually from some arbitrary namespace and ask for it to
# be registered.
if ( not any { $_ eq $plugin } @plugins ) {
push @plugins, $plugin;
}

return;
}

1;