4 package Visitor::NameTracking;
8 use namespace::clean -except => 'meta';
10 has '_current_trace_name' => (is => 'ro');
11 has 'root_name' => (is => 'ro');
14 my ($orig, $self) = (shift, shift);
15 local $self->{_current_trace_name}
16 = ($self->{_current_trace_name}||$self->root_name);
17 return $self->$orig(@_);
20 around visit_hash_entry => sub {
21 my ($orig, $self) = (shift, shift);
22 my $key = $_[0]; # $key, $value
23 local $self->{_current_trace_name}
24 = $self->{_current_trace_name}.'->{'.(perlstring $key).'}';
25 return $self->$orig(@_);
28 around visit_array_entry => sub {
29 my ($orig, $self) = (shift, shift);
30 my $index = $_[1]; # $value, $index
31 local $self->{_current_trace_name}
32 = $self->{_current_trace_name}.'->['.$index.']';
33 return $self->$orig(@_);
36 around visit_scalar => sub {
37 my ($orig, $self) = (shift, shift);
38 local $self->{_current_trace_name} = '${'.$self->{_current_trace_name}.'}';
39 return $self->$orig(@_);
45 use Scalar::Util qw(weaken refaddr);
46 use namespace::clean -except => 'meta';
48 extends 'Data::Visitor';
50 with 'Visitor::NameTracking';
52 # dump the lazy when we get a sensible version of D::V on the dev system
54 has '_traced_refs' => (is => 'ro', lazy => 1, default => sub { {} });
55 has '_traced_names' => (is => 'ro', lazy => 1, default => sub { {} });
57 before visit_ref => sub {
58 my ($self, $data) = @_;
60 # can't just rely on refaddr because it may get re-used if the data goes
61 # out of scope (we could play clever games with free magic on the wizard
62 # or whatever but KISS) - but we -can- keep a weak reference which will
63 # turn to undef if the variable disappears
65 weaken($self->_traced_refs->{refaddr $data} = $data);
67 $self->_traced_names->{refaddr $data} = $self->_current_trace_name;
72 my $refs = $self->_traced_refs;
73 my $names = $self->_traced_names;
75 # nuke keys where the traced refs entry is undef since they indicate
76 # "went out of scope" so the name is no longer valid. however if we
77 # do still have a refs entry we know the name is valid because if it
78 # didn't go out of scope that refaddr can't have been re-used.
79 # (NB: I don't care if this works under ithreads)
81 delete @{$names}{grep !defined($refs->{$_}), keys %$names};
85 # force recursion into objects (Data::Visitor doesn't by default)
87 sub visit_object { shift->visit_ref(@_) }
89 package Ref::Replacer;
91 # note: we actually handle weaken as well as external refs because I intend
92 # to use Data::Dumper as a first pass and YAML::XS as a second and neither
93 # of them know how to deal with weak references
95 # I'm faintly curious to see if manual cross-ref-ification nad JSON::XS will
96 # actually be faster for reconstructing structures but it's fairly academic
100 use Scalar::Util qw(refaddr isweak);
101 use namespace::clean -except => 'meta';
103 extends 'Data::Visitor';
105 # we need name tracking but have to apply the role at the end of the file
106 # so that our around modifiers end up within the name tracking around
107 # instead of outside - otherwise e.g. array value weakening goes wrong
109 has 'external_mappings' => (is => 'ro', lazy => 1, default => sub { {} });
110 has 'weaken_these' => (is => 'ro', lazy => 1, default => sub { {} });
111 has 'map_these' => (is => 'ro', lazy => 1, default => sub { {} });
113 around visit_ref => sub {
114 my ($orig, $self) = (shift, shift);
117 # if we've got a mapping for a reference (i.e. it's supplied from
118 # somewhere else) then we need to record where we are and then
119 # return undef for the fmap process so we serialize an undefined
120 # value and the fixup puts the external reference back in later
122 if (my $m = $self->external_mappings->{refaddr $value}) {
123 $self->map_these->{$self->_current_trace_name} = $m;
127 return $self->$orig(@_);
130 around visit_hash_value => sub {
131 my ($orig, $self) = (shift, shift);
132 my ($value, $key, $hash) = @_;
133 if (isweak $hash->{$key}) {
134 $self->weaken_these->{$self->_current_trace_name} = 1;
136 return $self->$orig(@_);
139 around visit_array_entry => sub {
140 my ($orig, $self) = (shift, shift);
141 my ($value, $index, $array) = @_;
142 if (isweak $array->[$index]) {
143 $self->weaken_these->{$self->_current_trace_name} = 1;
145 return $self->$orig(@_);
148 around visit_scalar => sub {
149 my ($orig, $self) = (shift, shift);
151 if (isweak $$scalar) {
152 $self->weaken_these->{$self->_current_trace_name} = 1;
154 return $self->$orig(@_);
157 # now it's safe to apply the role
159 with 'Visitor::NameTracking';
165 map $self->${\"_fixup_code_for_$_"},
166 qw(externals weakrefs)
170 sub _fixup_code_for_externals {
172 my $ext = $self->map_these;
173 return unless keys %$ext;
175 qq{# fixup code for external references},
177 $_.' = '.$ext->{$_}.';';
183 sub _fixup_code_for_weakrefs {
185 my $weaken = $self->weaken_these;
186 return unless keys %$weaken;
188 qq{# fixup code for weak references},
189 'use Scalar::Util ();',
191 'Scalar::Util::weaken('.$_.');';
197 # force recursion into objects (Data::Visitor doesn't by default)
199 sub visit_object { shift->visit_ref(@_) }
203 use Test::More qw(no_plan);
204 use Scalar::Util qw(refaddr weaken);
207 bar => { baz => [ 'quux', { fleem => 1 } ] },
208 skald => \[ { hot => 'story' } ],
211 my @expect = split "\n", <<'EOEXPECT';
216 ${$foo->{"skald"}}->[0]
219 my $tracer = Ref::Tracer->new({ root_name => '$foo' });
221 $tracer->visit($foo);
223 delete $foo->{bar}{baz};
225 my $result = $tracer->traced_ref_map;
229 [ sort { length($a) <=> length($b) } values %$result ],
230 "Expected results present"
233 my %map = reverse %$result;
235 foreach my $e (@expect) {
239 die "Error $@ evaluating $e" if $@;
242 is($map{$e},refaddr($value), "Result for ${e} ok");
246 one => { two => three },
247 bard => $foo->{skald},
248 bard_guts => ${$foo->{skald}},
249 empty_now => $foo->{bar},
252 weaken($flimflam->{weak_one} = $flimflam->{one});
253 weaken($flimflam->{weak_member}[0] = $flimflam->{bard});
254 weaken(${$flimflam->{weak_scalar}} = $flimflam->{bard_guts});
256 my $replacer = Ref::Replacer->new({
257 external_mappings => $result,
258 root_name => '$final',
261 my $copyflam = $replacer->visit($flimflam);
263 use Data::Dumper; $Data::Dumper::Indent = 1;
265 warn Dumper($copyflam);
267 warn $replacer->fixup_code;