summaryrefslogtreecommitdiff
path: root/Master/tlpkg/tlperl/lib/autodie
diff options
context:
space:
mode:
authorSiep Kroonenberg <siepo@cybercomm.nl>2011-02-17 17:57:31 +0000
committerSiep Kroonenberg <siepo@cybercomm.nl>2011-02-17 17:57:31 +0000
commit320d8694fec25ed148613684543b5a0504a046ae (patch)
tree0ddcf933d3acd3c98a387fa2bf73d0554ca6e50d /Master/tlpkg/tlperl/lib/autodie
parent779e71f16ca01a6244b632b95bdb461fec163b34 (diff)
New tlperl part XIV
git-svn-id: svn://tug.org/texlive/trunk@21436 c570f23f-e606-0410-a88d-b1316a301751
Diffstat (limited to 'Master/tlpkg/tlperl/lib/autodie')
-rw-r--r--Master/tlpkg/tlperl/lib/autodie/exception.pm741
-rw-r--r--Master/tlpkg/tlperl/lib/autodie/exception/system.pm81
-rw-r--r--Master/tlpkg/tlperl/lib/autodie/hints.pm598
3 files changed, 1420 insertions, 0 deletions
diff --git a/Master/tlpkg/tlperl/lib/autodie/exception.pm b/Master/tlpkg/tlperl/lib/autodie/exception.pm
new file mode 100644
index 00000000000..8646099c4c8
--- /dev/null
+++ b/Master/tlpkg/tlperl/lib/autodie/exception.pm
@@ -0,0 +1,741 @@
+package autodie::exception;
+use 5.008;
+use strict;
+use warnings;
+use Carp qw(croak);
+
+our $DEBUG = 0;
+
+use overload
+ q{""} => "stringify"
+;
+
+# Overload smart-match only if we're using 5.10
+
+use if ($] >= 5.010), overload => '~~' => "matches";
+
+our $VERSION = '2.06_01';
+
+my $PACKAGE = __PACKAGE__; # Useful to have a scalar for hash keys.
+
+=head1 NAME
+
+autodie::exception - Exceptions from autodying functions.
+
+=head1 SYNOPSIS
+
+ eval {
+ use autodie;
+
+ open(my $fh, '<', 'some_file.txt');
+
+ ...
+ };
+
+ if (my $E = $@) {
+ say "Ooops! ",$E->caller," had problems: $@";
+ }
+
+
+=head1 DESCRIPTION
+
+When an L<autodie> enabled function fails, it generates an
+C<autodie::exception> object. This can be interrogated to
+determine further information about the error that occurred.
+
+This document is broken into two sections; those methods that
+are most useful to the end-developer, and those methods for
+anyone wishing to subclass or get very familiar with
+C<autodie::exception>.
+
+=head2 Common Methods
+
+These methods are intended to be used in the everyday dealing
+of exceptions.
+
+The following assume that the error has been copied into
+a separate scalar:
+
+ if ($E = $@) {
+ ...
+ }
+
+This is not required, but is recommended in case any code
+is called which may reset or alter C<$@>.
+
+=cut
+
+=head3 args
+
+ my $array_ref = $E->args;
+
+Provides a reference to the arguments passed to the subroutine
+that died.
+
+=cut
+
+sub args { return $_[0]->{$PACKAGE}{args}; }
+
+=head3 function
+
+ my $sub = $E->function;
+
+The subroutine (including package) that threw the exception.
+
+=cut
+
+sub function { return $_[0]->{$PACKAGE}{function}; }
+
+=head3 file
+
+ my $file = $E->file;
+
+The file in which the error occurred (eg, C<myscript.pl> or
+C<MyTest.pm>).
+
+=cut
+
+sub file { return $_[0]->{$PACKAGE}{file}; }
+
+=head3 package
+
+ my $package = $E->package;
+
+The package from which the exceptional subroutine was called.
+
+=cut
+
+sub package { return $_[0]->{$PACKAGE}{package}; }
+
+=head3 caller
+
+ my $caller = $E->caller;
+
+The subroutine that I<called> the exceptional code.
+
+=cut
+
+sub caller { return $_[0]->{$PACKAGE}{caller}; }
+
+=head3 line
+
+ my $line = $E->line;
+
+The line in C<< $E->file >> where the exceptional code was called.
+
+=cut
+
+sub line { return $_[0]->{$PACKAGE}{line}; }
+
+=head3 context
+
+ my $context = $E->context;
+
+The context in which the subroutine was called. This can be
+'list', 'scalar', or undefined (unknown). It will never be 'void', as
+C<autodie> always captures the return value in one way or another.
+
+=cut
+
+sub context { return $_[0]->{$PACKAGE}{context} }
+
+=head3 return
+
+ my $return_value = $E->return;
+
+The value(s) returned by the failed subroutine. When the subroutine
+was called in a list context, this will always be a reference to an
+array containing the results. When the subroutine was called in
+a scalar context, this will be the actual scalar returned.
+
+=cut
+
+sub return { return $_[0]->{$PACKAGE}{return} }
+
+=head3 errno
+
+ my $errno = $E->errno;
+
+The value of C<$!> at the time when the exception occurred.
+
+B<NOTE>: This method will leave the main C<autodie::exception> class
+and become part of a role in the future. You should only call
+C<errno> for exceptions where C<$!> would reasonably have been
+set on failure.
+
+=cut
+
+# TODO: Make errno part of a role. It doesn't make sense for
+# everything.
+
+sub errno { return $_[0]->{$PACKAGE}{errno}; }
+
+=head3 eval_error
+
+ my $old_eval_error = $E->eval_error;
+
+The contents of C<$@> immediately after autodie triggered an
+exception. This may be useful when dealing with modules such
+as L<Text::Balanced> that set (but do not throw) C<$@> on error.
+
+=cut
+
+sub eval_error { return $_[0]->{$PACKAGE}{eval_error}; }
+
+=head3 matches
+
+ if ( $e->matches('open') ) { ... }
+
+ if ( $e ~~ 'open' ) { ... }
+
+C<matches> is used to determine whether a
+given exception matches a particular role. On Perl 5.10,
+using smart-match (C<~~>) with an C<autodie::exception> object
+will use C<matches> underneath.
+
+An exception is considered to match a string if:
+
+=over 4
+
+=item *
+
+For a string not starting with a colon, the string exactly matches the
+package and subroutine that threw the exception. For example,
+C<MyModule::log>. If the string does not contain a package name,
+C<CORE::> is assumed.
+
+=item *
+
+For a string that does start with a colon, if the subroutine
+throwing the exception I<does> that behaviour. For example, the
+C<CORE::open> subroutine does C<:file>, C<:io> and C<:all>.
+
+See L<autodie/CATEGORIES> for futher information.
+
+=back
+
+=cut
+
+{
+ my (%cache);
+
+ sub matches {
+ my ($this, $that) = @_;
+
+ # TODO - Handle references
+ croak "UNIMPLEMENTED" if ref $that;
+
+ my $sub = $this->function;
+
+ if ($DEBUG) {
+ my $sub2 = $this->function;
+ warn "Smart-matching $that against $sub / $sub2\n";
+ }
+
+ # Direct subname match.
+ return 1 if $that eq $sub;
+ return 1 if $that !~ /:/ and "CORE::$that" eq $sub;
+ return 0 if $that !~ /^:/;
+
+ # Cached match / check tags.
+ require Fatal;
+
+ if (exists $cache{$sub}{$that}) {
+ return $cache{$sub}{$that};
+ }
+
+ # This rather awful looking line checks to see if our sub is in the
+ # list of expanded tags, caches it, and returns the result.
+
+ return $cache{$sub}{$that} = grep { $_ eq $sub } @{ $this->_expand_tag($that) };
+ }
+}
+
+# This exists primarily so that child classes can override or
+# augment it if they wish.
+
+sub _expand_tag {
+ my ($this, @args) = @_;
+
+ return Fatal->_expand_tag(@args);
+}
+
+=head2 Advanced methods
+
+The following methods, while usable from anywhere, are primarily
+intended for developers wishing to subclass C<autodie::exception>,
+write code that registers custom error messages, or otherwise
+work closely with the C<autodie::exception> model.
+
+=cut
+
+# The table below records customer formatters.
+# TODO - Should this be a package var instead?
+# TODO - Should these be in a completely different file, or
+# perhaps loaded on demand? Most formatters will never
+# get used in most programs.
+
+my %formatter_of = (
+ 'CORE::close' => \&_format_close,
+ 'CORE::open' => \&_format_open,
+ 'CORE::dbmopen' => \&_format_dbmopen,
+ 'CORE::flock' => \&_format_flock,
+);
+
+# TODO: Our tests only check LOCK_EX | LOCK_NB is properly
+# formatted. Try other combinations and ensure they work
+# correctly.
+
+sub _format_flock {
+ my ($this) = @_;
+
+ require Fcntl;
+
+ my $filehandle = $this->args->[0];
+ my $raw_mode = $this->args->[1];
+
+ my $mode_type;
+ my $lock_unlock;
+
+ if ($raw_mode & Fcntl::LOCK_EX() ) {
+ $lock_unlock = "lock";
+ $mode_type = "for exclusive access";
+ }
+ elsif ($raw_mode & Fcntl::LOCK_SH() ) {
+ $lock_unlock = "lock";
+ $mode_type = "for shared access";
+ }
+ elsif ($raw_mode & Fcntl::LOCK_UN() ) {
+ $lock_unlock = "unlock";
+ $mode_type = "";
+ }
+ else {
+ # I've got no idea what they're trying to do.
+ $lock_unlock = "lock";
+ $mode_type = "with mode $raw_mode";
+ }
+
+ my $cooked_filehandle;
+
+ if ($filehandle and not ref $filehandle) {
+
+ # A package filehandle with a name!
+
+ $cooked_filehandle = " $filehandle";
+ }
+ else {
+ # Otherwise we have a scalar filehandle.
+
+ $cooked_filehandle = '';
+
+ }
+
+ local $! = $this->errno;
+
+ return "Can't $lock_unlock filehandle$cooked_filehandle $mode_type: $!";
+
+}
+
+# Default formatter for CORE::dbmopen
+sub _format_dbmopen {
+ my ($this) = @_;
+ my @args = @{$this->args};
+
+ # TODO: Presently, $args flattens out the (usually empty) hash
+ # which is passed as the first argument to dbmopen. This is
+ # a bug in our args handling code (taking a reference to it would
+ # be better), but for the moment we'll just examine the end of
+ # our arguments list for message formatting.
+
+ my $mode = $args[-1];
+ my $file = $args[-2];
+
+ # If we have a mask, then display it in octal, not decimal.
+ # We don't do this if it already looks octalish, or doesn't
+ # look like a number.
+
+ if ($mode =~ /^[^\D0]\d+$/) {
+ $mode = sprintf("0%lo", $mode);
+ };
+
+ local $! = $this->errno;
+
+ return "Can't dbmopen(%hash, '$file', $mode): '$!'";
+}
+
+# Default formatter for CORE::close
+
+sub _format_close {
+ my ($this) = @_;
+ my $close_arg = $this->args->[0];
+
+ local $! = $this->errno;
+
+ # If we've got an old-style filehandle, mention it.
+ if ($close_arg and not ref $close_arg) {
+ return "Can't close filehandle '$close_arg': '$!'";
+ }
+
+ # TODO - This will probably produce an ugly error. Test and fix.
+ return "Can't close($close_arg) filehandle: '$!'";
+
+}
+
+# Default formatter for CORE::open
+
+use constant _FORMAT_OPEN => "Can't open '%s' for %s: '%s'";
+
+sub _format_open_with_mode {
+ my ($this, $mode, $file, $error) = @_;
+
+ my $wordy_mode;
+
+ if ($mode eq '<') { $wordy_mode = 'reading'; }
+ elsif ($mode eq '>') { $wordy_mode = 'writing'; }
+ elsif ($mode eq '>>') { $wordy_mode = 'appending'; }
+
+ return sprintf _FORMAT_OPEN, $file, $wordy_mode, $error if $wordy_mode;
+
+ Carp::confess("Internal autodie::exception error: Don't know how to format mode '$mode'.");
+
+}
+
+sub _format_open {
+ my ($this) = @_;
+
+ my @open_args = @{$this->args};
+
+ # Use the default formatter for single-arg and many-arg open
+ if (@open_args <= 1 or @open_args >= 4) {
+ return $this->format_default;
+ }
+
+ # For two arg open, we have to extract the mode
+ if (@open_args == 2) {
+ my ($fh, $file) = @open_args;
+
+ if (ref($fh) eq "GLOB") {
+ $fh = '$fh';
+ }
+
+ my ($mode) = $file =~ m{
+ ^\s* # Spaces before mode
+ (
+ (?> # Non-backtracking subexp.
+ < # Reading
+ |>>? # Writing/appending
+ )
+ )
+ [^&] # Not an ampersand (which means a dup)
+ }x;
+
+ if (not $mode) {
+ # Maybe it's a 2-arg open without any mode at all?
+ # Detect the most simple case for this, where our
+ # file consists only of word characters.
+
+ if ( $file =~ m{^\s*\w+\s*$} ) {
+ $mode = '<'
+ }
+ else {
+ # Otherwise, we've got no idea what's going on.
+ # Use the default.
+ return $this->format_default;
+ }
+ }
+
+ # Localising $! means perl make make it a pretty error for us.
+ local $! = $this->errno;
+
+ return $this->_format_open_with_mode($mode, $file, $!);
+ }
+
+ # Here we must be using three arg open.
+
+ my $file = $open_args[2];
+
+ local $! = $this->errno;
+
+ my $mode = $open_args[1];
+
+ local $@;
+
+ my $msg = eval { $this->_format_open_with_mode($mode, $file, $!); };
+
+ return $msg if $msg;
+
+ # Default message (for pipes and odd things)
+
+ return "Can't open '$file' with mode '$open_args[1]': '$!'";
+}
+
+=head3 register
+
+ autodie::exception->register( 'CORE::open' => \&mysub );
+
+The C<register> method allows for the registration of a message
+handler for a given subroutine. The full subroutine name including
+the package should be used.
+
+Registered message handlers will receive the C<autodie::exception>
+object as the first parameter.
+
+=cut
+
+sub register {
+ my ($class, $symbol, $handler) = @_;
+
+ croak "Incorrect call to autodie::register" if @_ != 3;
+
+ $formatter_of{$symbol} = $handler;
+
+}
+
+=head3 add_file_and_line
+
+ say "Problem occurred",$@->add_file_and_line;
+
+Returns the string C< at %s line %d>, where C<%s> is replaced with
+the filename, and C<%d> is replaced with the line number.
+
+Primarily intended for use by format handlers.
+
+=cut
+
+# Simply produces the file and line number; intended to be added
+# to the end of error messages.
+
+sub add_file_and_line {
+ my ($this) = @_;
+
+ return sprintf(" at %s line %d\n", $this->file, $this->line);
+}
+
+=head3 stringify
+
+ say "The error was: ",$@->stringify;
+
+Formats the error as a human readable string. Usually there's no
+reason to call this directly, as it is used automatically if an
+C<autodie::exception> object is ever used as a string.
+
+Child classes can override this method to change how they're
+stringified.
+
+=cut
+
+sub stringify {
+ my ($this) = @_;
+
+ my $call = $this->function;
+
+ if ($DEBUG) {
+ my $dying_pkg = $this->package;
+ my $sub = $this->function;
+ my $caller = $this->caller;
+ warn "Stringifing exception for $dying_pkg :: $sub / $caller / $call\n";
+ }
+
+ # TODO - This isn't using inheritance. Should it?
+ if ( my $sub = $formatter_of{$call} ) {
+ return $sub->($this) . $this->add_file_and_line;
+ }
+
+ return $this->format_default . $this->add_file_and_line;
+
+}
+
+=head3 format_default
+
+ my $error_string = $E->format_default;
+
+This produces the default error string for the given exception,
+I<without using any registered message handlers>. It is primarily
+intended to be called from a message handler when they have
+been passed an exception they don't want to format.
+
+Child classes can override this method to change how default
+messages are formatted.
+
+=cut
+
+# TODO: This produces ugly errors. Is there any way we can
+# dig around to find the actual variable names? I know perl 5.10
+# does some dark and terrible magicks to find them for undef warnings.
+
+sub format_default {
+ my ($this) = @_;
+
+ my $call = $this->function;
+
+ local $! = $this->errno;
+
+ # TODO: This is probably a good idea for CORE, is it
+ # a good idea for other subs?
+
+ # Trim package name off dying sub for error messages.
+ $call =~ s/.*:://;
+
+ # Walk through all our arguments, and...
+ #
+ # * Replace undef with the word 'undef'
+ # * Replace globs with the string '$fh'
+ # * Quote all other args.
+
+ my @args = @{ $this->args() };
+
+ foreach my $arg (@args) {
+ if (not defined($arg)) { $arg = 'undef' }
+ elsif (ref($arg) eq "GLOB") { $arg = '$fh' }
+ else { $arg = qq{'$arg'} }
+ }
+
+ # Format our beautiful error.
+
+ return "Can't $call(". join(q{, }, @args) . "): $!" ;
+
+ # TODO - Handle user-defined errors from hash.
+
+ # TODO - Handle default error messages.
+
+}
+
+=head3 new
+
+ my $error = autodie::exception->new(
+ args => \@_,
+ function => "CORE::open",
+ errno => $!,
+ context => 'scalar',
+ return => undef,
+ );
+
+
+Creates a new C<autodie::exception> object. Normally called
+directly from an autodying function. The C<function> argument
+is required, its the function we were trying to call that
+generated the exception. The C<args> parameter is optional.
+
+The C<errno> value is optional. In versions of C<autodie::exception>
+1.99 and earlier the code would try to automatically use the
+current value of C<$!>, but this was unreliable and is no longer
+supported.
+
+Atrributes such as package, file, and caller are determined
+automatically, and cannot be specified.
+
+=cut
+
+sub new {
+ my ($class, @args) = @_;
+
+ my $this = {};
+
+ bless($this,$class);
+
+ # I'd love to use EVERY here, but it causes our code to die
+ # because it wants to stringify our objects before they're
+ # initialised, causing everything to explode.
+
+ $this->_init(@args);
+
+ return $this;
+}
+
+sub _init {
+
+ my ($this, %args) = @_;
+
+ # Capturing errno here is not necessarily reliable.
+ my $original_errno = $!;
+
+ our $init_called = 1;
+
+ my $class = ref $this;
+
+ # We're going to walk up our call stack, looking for the
+ # first thing that doesn't look like our exception
+ # code, autodie/Fatal, or some whacky eval.
+
+ my ($package, $file, $line, $sub);
+
+ my $depth = 0;
+
+ while (1) {
+ $depth++;
+
+ ($package, $file, $line, $sub) = CORE::caller($depth);
+
+ # Skip up the call stack until we find something outside
+ # of the Fatal/autodie/eval space.
+
+ next if $package->isa('Fatal');
+ next if $package->isa($class);
+ next if $package->isa(__PACKAGE__);
+ next if $file =~ /^\(eval\s\d+\)$/;
+
+ last;
+
+ }
+
+ # We now have everything correct, *except* for our subroutine
+ # name. If it's __ANON__ or (eval), then we need to keep on
+ # digging deeper into our stack to find the real name. However we
+ # don't update our other information, since that will be correct
+ # for our current exception.
+
+ my $first_guess_subroutine = $sub;
+
+ while (defined $sub and $sub =~ /^\(eval\)$|::__ANON__$/) {
+ $depth++;
+
+ $sub = (CORE::caller($depth))[3];
+ }
+
+ # If we end up falling out the bottom of our stack, then our
+ # __ANON__ guess is the best we can get. This includes situations
+ # where we were called from the top level of a program.
+
+ if (not defined $sub) {
+ $sub = $first_guess_subroutine;
+ }
+
+ $this->{$PACKAGE}{package} = $package;
+ $this->{$PACKAGE}{file} = $file;
+ $this->{$PACKAGE}{line} = $line;
+ $this->{$PACKAGE}{caller} = $sub;
+ $this->{$PACKAGE}{package} = $package;
+
+ $this->{$PACKAGE}{errno} = $args{errno} || 0;
+
+ $this->{$PACKAGE}{context} = $args{context};
+ $this->{$PACKAGE}{return} = $args{return};
+ $this->{$PACKAGE}{eval_error} = $args{eval_error};
+
+ $this->{$PACKAGE}{args} = $args{args} || [];
+ $this->{$PACKAGE}{function}= $args{function} or
+ croak("$class->new() called without function arg");
+
+ return $this;
+
+}
+
+1;
+
+__END__
+
+=head1 SEE ALSO
+
+L<autodie>, L<autodie::exception::system>
+
+=head1 LICENSE
+
+Copyright (C)2008 Paul Fenwick
+
+This is free software. You may modify and/or redistribute this
+code under the same terms as Perl 5.10 itself, or, at your option,
+any later version of Perl 5.
+
+=head1 AUTHOR
+
+Paul Fenwick E<lt>pjf@perltraining.com.auE<gt>
diff --git a/Master/tlpkg/tlperl/lib/autodie/exception/system.pm b/Master/tlpkg/tlperl/lib/autodie/exception/system.pm
new file mode 100644
index 00000000000..07cd1c9a038
--- /dev/null
+++ b/Master/tlpkg/tlperl/lib/autodie/exception/system.pm
@@ -0,0 +1,81 @@
+package autodie::exception::system;
+use 5.008;
+use strict;
+use warnings;
+use base 'autodie::exception';
+use Carp qw(croak);
+
+our $VERSION = '2.06_01';
+
+my $PACKAGE = __PACKAGE__;
+
+=head1 NAME
+
+autodie::exception::system - Exceptions from autodying system().
+
+=head1 SYNOPSIS
+
+ eval {
+ use autodie qw(system);
+
+ system($cmd, @args);
+
+ };
+
+ if (my $E = $@) {
+ say "Ooops! ",$E->caller," had problems: $@";
+ }
+
+
+=head1 DESCRIPTION
+
+This is a L<autodie::exception> class for failures from the
+C<system> command.
+
+Presently there is no way to interrogate an C<autodie::exception::system>
+object for the command, exit status, and other information you'd expect
+such an object to hold. The interface will be expanded to accommodate
+this in the future.
+
+=cut
+
+sub _init {
+ my ($this, %args) = @_;
+
+ $this->{$PACKAGE}{message} = $args{message}
+ || croak "'message' arg not supplied to autodie::exception::system->new";
+
+ return $this->SUPER::_init(%args);
+
+}
+
+=head2 stringify
+
+When stringified, C<autodie::exception::system> objects currently
+use the message generated by L<IPC::System::Simple>.
+
+=cut
+
+sub stringify {
+
+ my ($this) = @_;
+
+ return $this->{$PACKAGE}{message} . $this->add_file_and_line;
+
+}
+
+1;
+
+__END__
+
+=head1 LICENSE
+
+Copyright (C)2008 Paul Fenwick
+
+This is free software. You may modify and/or redistribute this
+code under the same terms as Perl 5.10 itself, or, at your option,
+any later version of Perl 5.
+
+=head1 AUTHOR
+
+Paul Fenwick E<lt>pjf@perltraining.com.auE<gt>
diff --git a/Master/tlpkg/tlperl/lib/autodie/hints.pm b/Master/tlpkg/tlperl/lib/autodie/hints.pm
new file mode 100644
index 00000000000..e7be03a047a
--- /dev/null
+++ b/Master/tlpkg/tlperl/lib/autodie/hints.pm
@@ -0,0 +1,598 @@
+package autodie::hints;
+
+use strict;
+use warnings;
+
+use constant PERL58 => ( $] < 5.009 );
+
+our $VERSION = '2.06_01';
+
+=head1 NAME
+
+autodie::hints - Provide hints about user subroutines to autodie
+
+=head1 SYNOPSIS
+
+ package Your::Module;
+
+ our %DOES = ( 'autodie::hints::provider' => 1 );
+
+ sub AUTODIE_HINTS {
+ return {
+ foo => { scalar => HINTS, list => SOME_HINTS },
+ bar => { scalar => HINTS, list => MORE_HINTS },
+ }
+ }
+
+ # Later, in your main program...
+
+ use Your::Module qw(foo bar);
+ use autodie qw(:default foo bar);
+
+ foo(); # succeeds or dies based on scalar hints
+
+ # Alternatively, hints can be set on subroutines we've
+ # imported.
+
+ use autodie::hints;
+ use Some::Module qw(think_positive);
+
+ BEGIN {
+ autodie::hints->set_hints_for(
+ \&think_positive,
+ {
+ fail => sub { $_[0] <= 0 }
+ }
+ )
+ }
+ use autodie qw(think_positive);
+
+ think_positive(...); # Returns positive or dies.
+
+
+=head1 DESCRIPTION
+
+=head2 Introduction
+
+The L<autodie> pragma is very smart when it comes to working with
+Perl's built-in functions. The behaviour for these functions are
+fixed, and C<autodie> knows exactly how they try to signal failure.
+
+But what about user-defined subroutines from modules? If you use
+C<autodie> on a user-defined subroutine then it assumes the following
+behaviour to demonstrate failure:
+
+=over
+
+=item *
+
+A false value, in scalar context
+
+=item *
+
+An empty list, in list context
+
+=item *
+
+A list containing a single undef, in list context
+
+=back
+
+All other return values (including the list of the single zero, and the
+list containing a single empty string) are considered successful. However,
+real-world code isn't always that easy. Perhaps the code you're working
+with returns a string containing the word "FAIL" upon failure, or a
+two element list containing C<(undef, "human error message")>. To make
+autodie work with these sorts of subroutines, we have
+the I<hinting interface>.
+
+The hinting interface allows I<hints> to be provided to C<autodie>
+on how it should detect failure from user-defined subroutines. While
+these I<can> be provided by the end-user of C<autodie>, they are ideally
+written into the module itself, or into a helper module or sub-class
+of C<autodie> itself.
+
+=head2 What are hints?
+
+A I<hint> is a subroutine or value that is checked against the
+return value of an autodying subroutine. If the match returns true,
+C<autodie> considers the subroutine to have failed.
+
+If the hint provided is a subroutine, then C<autodie> will pass
+the complete return value to that subroutine. If the hint is
+any other value, then C<autodie> will smart-match against the
+value provided. In Perl 5.8.x there is no smart-match operator, and as such
+only subroutine hints are supported in these versions.
+
+Hints can be provided for both scalar and list contexts. Note
+that an autodying subroutine will never see a void context, as
+C<autodie> always needs to capture the return value for examination.
+Autodying subroutines called in void context act as if they're called
+in a scalar context, but their return value is discarded after it
+has been checked.
+
+=head2 Example hints
+
+Hints may consist of scalars, array references, regular expressions and
+subroutine references. You can specify different hints for how
+failure should be identified in scalar and list contexts.
+
+These examples apply for use in the C<AUTODIE_HINTS> subroutine and when
+calling C<autodie::hints->set_hints_for()>.
+
+The most common context-specific hints are:
+
+ # Scalar failures always return undef:
+ { scalar => undef }
+
+ # Scalar failures return any false value [default expectation]:
+ { scalar => sub { ! $_[0] } }
+
+ # Scalar failures always return zero explicitly:
+ { scalar => '0' }
+
+ # List failures always return an empty list:
+ { list => [] }
+
+ # List failures return () or (undef) [default expectation]:
+ { list => sub { ! @_ || @_ == 1 && !defined $_[0] } }
+
+ # List failures return () or a single false value:
+ { list => sub { ! @_ || @_ == 1 && !$_[0] } }
+
+ # List failures return (undef, "some string")
+ { list => sub { @_ == 2 && !defined $_[0] } }
+
+ # Unsuccessful foo() returns 'FAIL' or '_FAIL' in scalar context,
+ # returns (-1) in list context...
+ autodie::hints->set_hints_for(
+ \&foo,
+ {
+ scalar => qr/^ _? FAIL $/xms,
+ list => [-1],
+ }
+ );
+
+ # Unsuccessful foo() returns 0 in all contexts...
+ autodie::hints->set_hints_for(
+ \&foo,
+ {
+ scalar => 0,
+ list => [0],
+ }
+ );
+
+This "in all contexts" construction is very common, and can be
+abbreviated, using the 'fail' key. This sets both the C<scalar>
+and C<list> hints to the same value:
+
+ # Unsuccessful foo() returns 0 in all contexts...
+ autodie::hints->set_hints_for(
+ \&foo,
+ {
+ fail => sub { @_ == 1 and defined $_[0] and $_[0] == 0 }
+ }
+ );
+
+ # Unsuccessful think_positive() returns negative number on failure...
+ autodie::hints->set_hints_for(
+ \&think_positive,
+ {
+ fail => sub { $_[0] < 0 }
+ }
+ );
+
+ # Unsuccessful my_system() returns non-zero on failure...
+ autodie::hints->set_hints_for(
+ \&my_system,
+ {
+ fail => sub { $_[0] != 0 }
+ }
+ );
+
+=head1 Manually setting hints from within your program
+
+If you are using a module which returns something special on failure, then
+you can manually create hints for each of the desired subroutines. Once
+the hints are specified, they are available for all files and modules loaded
+thereafter, thus you can move this work into a module and it will still
+work.
+
+ use Some::Module qw(foo bar);
+ use autodie::hints;
+
+ autodie::hints->set_hints_for(
+ \&foo,
+ {
+ scalar => SCALAR_HINT,
+ list => LIST_HINT,
+ }
+ );
+ autodie::hints->set_hints_for(
+ \&bar,
+ { fail => SOME_HINT, }
+ );
+
+It is possible to pass either a subroutine reference (recommended) or a fully
+qualified subroutine name as the first argument. This means you can set hints
+on modules that I<might> get loaded:
+
+ use autodie::hints;
+ autodie::hints->set_hints_for(
+ 'Some::Module:bar', { fail => SCALAR_HINT, }
+ );
+
+This technique is most useful when you have a project that uses a
+lot of third-party modules. You can define all your possible hints
+in one-place. This can even be in a sub-class of autodie. For
+example:
+
+ package my::autodie;
+
+ use parent qw(autodie);
+ use autodie::hints;
+
+ autodie::hints->set_hints_for(...);
+
+ 1;
+
+You can now C<use my::autodie>, which will work just like the standard
+C<autodie>, but is now aware of any hints that you've set.
+
+=head1 Adding hints to your module
+
+C<autodie> provides a passive interface to allow you to declare hints for
+your module. These hints will be found and used by C<autodie> if it
+is loaded, but otherwise have no effect (or dependencies) without autodie.
+To set these, your module needs to declare that it I<does> the
+C<autodie::hints::provider> role. This can be done by writing your
+own C<DOES> method, using a system such as C<Class::DOES> to handle
+the heavy-lifting for you, or declaring a C<%DOES> package variable
+with a C<autodie::hints::provider> key and a corresponding true value.
+
+Note that checking for a C<%DOES> hash is an C<autodie>-only
+short-cut. Other modules do not use this mechanism for checking
+roles, although you can use the C<Class::DOES> module from the
+CPAN to allow it.
+
+In addition, you must define a C<AUTODIE_HINTS> subroutine that returns
+a hash-reference containing the hints for your subroutines:
+
+ package Your::Module;
+
+ # We can use the Class::DOES from the CPAN to declare adherence
+ # to a role.
+
+ use Class::DOES 'autodie::hints::provider' => 1;
+
+ # Alternatively, we can declare the role in %DOES. Note that
+ # this is an autodie specific optimisation, although Class::DOES
+ # can be used to promote this to a true role declaration.
+
+ our %DOES = ( 'autodie::hints::provider' => 1 );
+
+ # Finally, we must define the hints themselves.
+
+ sub AUTODIE_HINTS {
+ return {
+ foo => { scalar => HINTS, list => SOME_HINTS },
+ bar => { scalar => HINTS, list => MORE_HINTS },
+ baz => { fail => HINTS },
+ }
+ }
+
+This allows your code to set hints without relying on C<autodie> and
+C<autodie::hints> being loaded, or even installed. In this way your
+code can do the right thing when C<autodie> is installed, but does not
+need to depend upon it to function.
+
+=head1 Insisting on hints
+
+When a user-defined subroutine is wrapped by C<autodie>, it will
+use hints if they are available, and otherwise reverts to the
+I<default behaviour> described in the introduction of this document.
+This can be problematic if we expect a hint to exist, but (for
+whatever reason) it has not been loaded.
+
+We can ask autodie to I<insist> that a hint be used by prefixing
+an exclamation mark to the start of the subroutine name. A lone
+exclamation mark indicates that I<all> subroutines after it must
+have hints declared.
+
+ # foo() and bar() must have their hints defined
+ use autodie qw( !foo !bar baz );
+
+ # Everything must have hints (recommended).
+ use autodie qw( ! foo bar baz );
+
+ # bar() and baz() must have their hints defined
+ use autodie qw( foo ! bar baz );
+
+ # Enable autodie for all of Perl's supported built-ins,
+ # as well as for foo(), bar() and baz(). Everything must
+ # have hints.
+ use autodie qw( ! :all foo bar baz );
+
+If hints are not available for the specified subroutines, this will cause a
+compile-time error. Insisting on hints for Perl's built-in functions
+(eg, C<open> and C<close>) is always successful.
+
+Insisting on hints is I<strongly> recommended.
+
+=cut
+
+# TODO: implement regular expression hints
+
+use constant UNDEF_ONLY => sub { not defined $_[0] };
+use constant EMPTY_OR_UNDEF => sub {
+ ! @_ or
+ @_==1 && !defined $_[0]
+};
+
+use constant EMPTY_ONLY => sub { @_ == 0 };
+use constant EMPTY_OR_FALSE => sub {
+ ! @_ or
+ @_==1 && !$_[0]
+};
+
+use constant SINGLE_TRUE => sub { @_ == 1 and not $_[0] };
+
+use constant DEFAULT_HINTS => {
+ scalar => UNDEF_ONLY,
+ list => EMPTY_OR_UNDEF,
+};
+
+
+use constant HINTS_PROVIDER => 'autodie::hints::provider';
+
+use base qw(Exporter);
+
+our $DEBUG = 0;
+
+# Only ( undef ) is a strange but possible situation for very
+# badly written code. It's not supported yet.
+
+my %Hints = (
+ 'File::Copy::copy' => { scalar => SINGLE_TRUE, list => SINGLE_TRUE },
+ 'File::Copy::move' => { scalar => SINGLE_TRUE, list => SINGLE_TRUE },
+ 'File::Copy::cp' => { scalar => SINGLE_TRUE, list => SINGLE_TRUE },
+ 'File::Copy::mv' => { scalar => SINGLE_TRUE, list => SINGLE_TRUE },
+);
+
+# Start by using Sub::Identify if it exists on this system.
+
+eval { require Sub::Identify; Sub::Identify->import('get_code_info'); };
+
+# If it doesn't exist, we'll define our own. This code is directly
+# taken from Rafael Garcia's Sub::Identify 0.04, used under the same
+# license as Perl itself.
+
+if ($@) {
+ require B;
+
+ no warnings 'once';
+
+ *get_code_info = sub ($) {
+
+ my ($coderef) = @_;
+ ref $coderef or return;
+ my $cv = B::svref_2object($coderef);
+ $cv->isa('B::CV') or return;
+ # bail out if GV is undefined
+ $cv->GV->isa('B::SPECIAL') and return;
+
+ return ($cv->GV->STASH->NAME, $cv->GV->NAME);
+ };
+
+}
+
+sub sub_fullname {
+ return join( '::', get_code_info( $_[1] ) );
+}
+
+my %Hints_loaded = ();
+
+sub load_hints {
+ my ($class, $sub) = @_;
+
+ my ($package) = ( $sub =~ /(.*)::/ );
+
+ if (not defined $package) {
+ require Carp;
+ Carp::croak(
+ "Internal error in autodie::hints::load_hints - no package found.
+ ");
+ }
+
+ # Do nothing if we've already tried to load hints for
+ # this package.
+ return if $Hints_loaded{$package}++;
+
+ my $hints_available = 0;
+
+ {
+ no strict 'refs'; ## no critic
+
+ if ($package->can('DOES') and $package->DOES(HINTS_PROVIDER) ) {
+ $hints_available = 1;
+ }
+ elsif ( PERL58 and $package->isa(HINTS_PROVIDER) ) {
+ $hints_available = 1;
+ }
+ elsif ( ${"${package}::DOES"}{HINTS_PROVIDER.""} ) {
+ $hints_available = 1;
+ }
+ }
+
+ return if not $hints_available;
+
+ my %package_hints = %{ $package->AUTODIE_HINTS };
+
+ foreach my $sub (keys %package_hints) {
+
+ my $hint = $package_hints{$sub};
+
+ # Ensure we have a package name.
+ $sub = "${package}::$sub" if $sub !~ /::/;
+
+ # TODO - Currently we don't check for conflicts, should we?
+ $Hints{$sub} = $hint;
+
+ $class->normalise_hints(\%Hints, $sub);
+ }
+
+ return;
+
+}
+
+sub normalise_hints {
+ my ($class, $hints, $sub) = @_;
+
+ if ( exists $hints->{$sub}->{fail} ) {
+
+ if ( exists $hints->{$sub}->{scalar} or
+ exists $hints->{$sub}->{list}
+ ) {
+ # TODO: Turn into a proper diagnostic.
+ require Carp;
+ local $Carp::CarpLevel = 1;
+ Carp::croak("fail hints cannot be provided with either scalar or list hints for $sub");
+ }
+
+ # Set our scalar and list hints.
+
+ $hints->{$sub}->{scalar} =
+ $hints->{$sub}->{list} = delete $hints->{$sub}->{fail};
+
+ return;
+
+ }
+
+ # Check to make sure all our hints exist.
+
+ foreach my $hint (qw(scalar list)) {
+ if ( not exists $hints->{$sub}->{$hint} ) {
+ # TODO: Turn into a proper diagnostic.
+ require Carp;
+ local $Carp::CarpLevel = 1;
+ Carp::croak("$hint hint missing for $sub");
+ }
+ }
+
+ return;
+}
+
+sub get_hints_for {
+ my ($class, $sub) = @_;
+
+ my $subname = $class->sub_fullname( $sub );
+
+ # If we have hints loaded for a sub, then return them.
+
+ if ( exists $Hints{ $subname } ) {
+ return $Hints{ $subname };
+ }
+
+ # If not, we try to load them...
+
+ $class->load_hints( $subname );
+
+ # ...and try again!
+
+ if ( exists $Hints{ $subname } ) {
+ return $Hints{ $subname };
+ }
+
+ # It's the caller's responsibility to use defaults if desired.
+ # This allows on autodie to insist on hints if needed.
+
+ return;
+
+}
+
+sub set_hints_for {
+ my ($class, $sub, $hints) = @_;
+
+ if (ref $sub) {
+ $sub = $class->sub_fullname( $sub );
+
+ require Carp;
+
+ $sub or Carp::croak("Attempts to set_hints_for unidentifiable subroutine");
+ }
+
+ if ($DEBUG) {
+ warn "autodie::hints: Setting $sub to hints: $hints\n";
+ }
+
+ $Hints{ $sub } = $hints;
+
+ $class->normalise_hints(\%Hints, $sub);
+
+ return;
+}
+
+1;
+
+__END__
+
+
+=head1 Diagnostics
+
+=over 4
+
+=item Attempts to set_hints_for unidentifiable subroutine
+
+You've called C<< autodie::hints->set_hints_for() >> using a subroutine
+reference, but that reference could not be resolved back to a
+subroutine name. It may be an anonymous subroutine (which can't
+be made autodying), or may lack a name for other reasons.
+
+If you receive this error with a subroutine that has a real name,
+then you may have found a bug in autodie. See L<autodie/BUGS>
+for how to report this.
+
+=item fail hints cannot be provided with either scalar or list hints for %s
+
+When defining hints, you can either supply both C<list> and
+C<scalar> keywords, I<or> you can provide a single C<fail> keyword.
+You can't mix and match them.
+
+=item %s hint missing for %s
+
+You've provided either a C<scalar> hint without supplying
+a C<list> hint, or vice-versa. You I<must> supply both C<scalar>
+and C<list> hints, I<or> a single C<fail> hint.
+
+=back
+
+=head1 ACKNOWLEDGEMENTS
+
+=over
+
+=item *
+
+Dr Damian Conway for suggesting the hinting interface and providing the
+example usage.
+
+=item *
+
+Jacinta Richardson for translating much of my ideas into this
+documentation.
+
+=back
+
+=head1 AUTHOR
+
+Copyright 2009, Paul Fenwick E<lt>pjf@perltraining.com.auE<gt>
+
+=head1 LICENSE
+
+This module is free software. You may distribute it under the
+same terms as Perl itself.
+
+=head1 SEE ALSO
+
+L<autodie>, L<Class::DOES>
+
+=cut