From e55803fce07b2fda98971fcb17698eef8a2fe4bb Mon Sep 17 00:00:00 2001
From: Jesse Luehrs <doy@tozt.net>
Date: Sun, 13 Jun 2010 11:55:28 -0500
Subject: add get_or_add_package_symbol, for the vivify behavior

---
 lib/Package/Stash.pm | 31 +++++++++++++++++++++++++++++--
 t/004-get.t          | 18 ++++++++++++++++++
 2 files changed, 47 insertions(+), 2 deletions(-)

diff --git a/lib/Package/Stash.pm b/lib/Package/Stash.pm
index 6b95340..6396ed5 100644
--- a/lib/Package/Stash.pm
+++ b/lib/Package/Stash.pm
@@ -226,7 +226,7 @@ Returns the value of the given package variable (including sigil).
 =cut
 
 sub get_package_symbol {
-    my ($self, $variable) = @_;
+    my ($self, $variable, %opts) = @_;
 
     my ($name, $sigil, $type) = ref $variable eq 'HASH'
         ? @{$variable}{qw[name sigil type]}
@@ -235,7 +235,22 @@ sub get_package_symbol {
     my $namespace = $self->namespace;
 
     if (!exists $namespace->{$name}) {
-        $self->add_package_symbol($variable)
+        # assigning to the result of this function like
+        #   @{$stash->get_package_symbol('@ISA')} = @new_ISA
+        # makes the result not visible until the variable is explicitly
+        # accessed... in the case of @ISA, this might never happen
+        # for instance, assigning like that and then calling $obj->isa
+        # will fail. see t/005-isa.t
+        if ($opts{vivify} && $type eq 'ARRAY' && $name ne 'ISA') {
+            $self->add_package_symbol($variable, []);
+        }
+        elsif ($opts{vivify} && $type eq 'HASH') {
+            $self->add_package_symbol($variable, {});
+        }
+        else {
+            # FIXME
+            $self->add_package_symbol($variable)
+        }
     }
 
     my $entry_ref = \$namespace->{$name};
@@ -254,6 +269,18 @@ sub get_package_symbol {
     }
 }
 
+=head2 get_or_add_package_symbol $variable
+
+Like C<get_package_symbol>, except that it will return an empty hashref or
+arrayref if the variable doesn't exist.
+
+=cut
+
+sub get_or_add_package_symbol {
+    my $self = shift;
+    $self->get_package_symbol(@_, vivify => 1);
+}
+
 =head2 remove_package_symbol $variable
 
 Removes the package variable described by C<$variable> (which includes the
diff --git a/t/004-get.t b/t/004-get.t
index 89d7567..ebeb864 100644
--- a/t/004-get.t
+++ b/t/004-get.t
@@ -45,4 +45,22 @@ use Package::Stash;
     }
 }
 
+{
+    my $stash = Package::Stash->new('Baz');
+    my $val = $stash->get_or_add_package_symbol('%foo');
+    is(ref($val), 'HASH', "got something");
+    $val->{bar} = 1;
+    is_deeply($stash->get_or_add_package_symbol('%foo'), {bar => 1},
+            "got the right variable");
+}
+
+{
+    my $stash = Package::Stash->new('Quux');
+    my $val = $stash->get_or_add_package_symbol('@foo');
+    is(ref($val), 'ARRAY', "got something");
+    push @$val, 1;
+    is_deeply($stash->get_or_add_package_symbol('@foo'), [1],
+            "got the right variable");
+}
+
 done_testing;
-- 
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