From: Stevan Little <stevan.little@iinteractive.com>
Date: Sat, 1 Jul 2006 20:57:11 +0000 (+0000)
Subject: applying patch from Robert Norris for next::can
X-Git-Tag: 0.13~5
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=322a5920b5c506789a9daf817374fd9f0df20ab5;p=gitmo%2FClass-C3.git

applying patch from Robert Norris for next::can
---

diff --git a/ChangeLog b/ChangeLog
index b0c5be6..68cdefb 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -2,6 +2,9 @@ Revision history for Perl extension Class::C3.
 
 0.12
     - clarifying docs for &initialize (thanks jcs)
+    - applying patch from Robert Norris to add 
+      next::can() functionality which allows safe 
+      probing of the presence of the next method
 
 0.11 Thurs. Feb 23, 2006
     - added some more tests for edge cases
diff --git a/lib/Class/C3.pm b/lib/Class/C3.pm
index bd72a00..a2f4740 100644
--- a/lib/Class/C3.pm
+++ b/lib/Class/C3.pm
@@ -158,8 +158,8 @@ our $VERSION = '0.05';
 
 our %METHOD_CACHE;
 
-sub method {
-    my $level = 1;
+sub _find {
+    my $level = 2;
     my ($method_caller, $label, @label);
     while ($method_caller = (caller($level++))[3]) {
       @label = (split '::', $method_caller);
@@ -172,28 +172,32 @@ sub method {
     my $self     = $_[0];
     my $class    = blessed($self) || $self;
     
-    goto &{ $METHOD_CACHE{"$class|$caller|$label"} ||= do {
-
-      my @MRO = Class::C3::calculateMRO($class);
-
-      my $current;
-      while ($current = shift @MRO) {
-          last if $caller eq $current;
-      }
-
-      no strict 'refs';
-      my $found;
-      foreach my $class (@MRO) {
-          next if (defined $Class::C3::MRO{$class} && 
-                   defined $Class::C3::MRO{$class}{methods}{$label});          
-          last if (defined ($found = *{$class . '::' . $label}{CODE}));
-      }
+    return $METHOD_CACHE{"$class|$caller|$label"} ||= do {
+        
+        my @MRO = Class::C3::calculateMRO($class);
+        
+        my $current;
+        while ($current = shift @MRO) {
+            last if $caller eq $current;
+        }
+        
+        no strict 'refs';
+        my $found;
+        foreach my $class (@MRO) {
+            next if (defined $Class::C3::MRO{$class} && 
+                     defined $Class::C3::MRO{$class}{methods}{$label});          
+            last if (defined ($found = *{$class . '::' . $label}{CODE}));
+        }
+        
+        die "No next::method '$label' found for $_[0]" if $_[1] && !$found;
+        
+        $found;
+    };
+}
 
-      die "No next::method '$label' found for $self" unless $found;
+sub method { goto &{_find($_[0], 1)} }
 
-      $found;
-    } };
-}
+sub can { return _find($_[0], 0) ? 1 : 0 }
 
 1;
 
@@ -397,6 +401,12 @@ that you cannot dispatch to a method of a different name (this is how C<NEXT::>
 The next thing to keep in mind is that you will need to pass all arguments to C<next::method> it can 
 not automatically use the current C<@_>. 
 
+If C<next::method> cannot find a next method to re-dispatch the call to, it will throw an exception.
+You can use C<next::can> to see if C<next::method> will succeed before you call it like so:
+
+  $self->next::method(@_) if $self->next::can; 
+
+
 There are some caveats about using C<next::method>, see below for those.
 
 =head1 CAVEATS
diff --git a/t/31_next_method_skip.t b/t/31_next_method_skip.t
index 26912f0..9bf2a2a 100644
--- a/t/31_next_method_skip.t
+++ b/t/31_next_method_skip.t
@@ -3,7 +3,7 @@
 use strict;
 use warnings;
 
-use Test::More tests => 7;
+use Test::More tests => 9;
 
 BEGIN {
     use lib 'opt', '../opt', '..';    
@@ -42,7 +42,8 @@ This tests the classic diamond inheritence pattern.
     use c3;    
     use base 'Diamond_A';     
     sub foo { 'Diamond_C::foo' }   
-    sub buz { 'Diamond_C::buz' }           
+    sub buz { 'Diamond_C::buz' }         
+    sub woz { 'Diamond_C::woz' }  
 }
 {
     package Diamond_D;
@@ -51,7 +52,9 @@ This tests the classic diamond inheritence pattern.
     sub foo { 'Diamond_D::foo => ' . (shift)->next::method() } 
     sub bar { 'Diamond_D::bar => ' . (shift)->next::method() }   
     sub buz { 'Diamond_D::buz => ' . (shift)->baz() }  
-    sub fuz { 'Diamond_D::fuz => ' . (shift)->next::method() }           
+    sub fuz { 'Diamond_D::fuz => ' . (shift)->next::method() }
+    sub woz { 'Diamond_D::woz can => ' . (shift)->next::can() }
+    sub noz { 'Diamond_D::noz can => ' . (shift)->next::can() }               
 
 }
 
@@ -69,4 +72,5 @@ is(Diamond_D->buz, 'Diamond_D::buz => Diamond_B::baz => Diamond_A::baz', '... ca
 eval { Diamond_D->fuz };
 like($@, qr/^No next::method 'fuz' found for Diamond_D/, '... cannot re-dispatch to a method which is not there');
 
-
+is(Diamond_D->woz, 'Diamond_D::woz can => 1', '... can re-dispatch figured out correctly');
+is(Diamond_D->noz, 'Diamond_D::noz can => 0', '... cannot re-dispatch figured out correctly');