Properly vivify nonexistent glob slots

[perl/modules/Scope-Upper.git] / lib / Scope / Upper.pm

diff --git a/lib/Scope/Upper.pm b/lib/Scope/Upper.pm
index 51cc4c48baad4535d26f83d48de2df56b3711b2b..84de02eea6ebf8befe98320881ff7d27f3d421fa 100644 (file)
--- a/lib/Scope/Upper.pm
+++ b/lib/Scope/Upper.pm
@@ -144,11 +144,27 @@ will set C<$x> to a reference to the string C<'foo'>.
 Other sigils (C<'@'>, C<'%'>, C<'&'> and C<'*'>) require C<$value> to be a reference of the corresponding type.
 
 When the symbol is given by a string, it is resolved when the actual localization takes place and not when C<localize> is called.
-This means that
+Thus, if the symbol name is not qualified, it will refer to the variable in the package where the localization actually takes place and not in the one where the C<localize> call was compiled.
+For example,
 
-    sub tag { localize '$x', $_[0] => UP }
+    {
+     package Scope;
+     sub new { localize '$tag', $_[0] => UP }
+    }
 
-will localize in the caller's namespace.
+    {
+     package Tool;
+     {
+      Scope->new;
+      ...
+     }
+    }
+
+will localize C<$Tool::tag> and not C<$Scope::tag>.
+
+Note that if C<$what> is a string denoting a variable that wasn't declared beforehand, the relevant slot will be vivified as needed and won't be deleted from the glob when the localization ends.
+This situation never arises with C<local> because it only compiles when the localized variable is already declared.
+Although I believe it shouldn't be a problem as glob slots definedness is pretty much an implementation detail, this behaviour may change in the future if proved harmful.
 
 =back
 
@@ -158,6 +174,8 @@ Similar to L</localize> but for array and hash elements.
 If C<$what> is a glob, the slot to fill is determined from which type of reference C<$value> is ; otherwise it's inferred from the sigil.
 C<$key> is either an array index or a hash key, depending of which kind of variable you localize.
 
+Just like for L</localize>, when C<$what> is a string pointing to an undeclared variable, it will be vivified but the variable itself will be empty when the localization ends (although it will still exist in its parent glob).
+
 =head2 C<localize_delete $what, $key, $context>
 
 Similiar to L</localize>, but for deleting variables or array/hash elements.