X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2Fbase.pm;h=be4c667e674f60f31a3a5d4d0f98a1dfb1fe413c;hb=d81018543234fe5f8d429eb7048c0b50792ea031;hp=4d1b18aa129b5f9148a1ccb9a69f649c0435ff5d;hpb=33d611b95de5d73b0d9e468de10111f460543b11;p=p5sagit%2Fp5-mst-13.2.git

diff --git a/lib/base.pm b/lib/base.pm
index 4d1b18a..be4c667 100644
--- a/lib/base.pm
+++ b/lib/base.pm
@@ -1,7 +1,8 @@
 package base;
 
+use strict 'vars';
 use vars qw($VERSION);
-$VERSION = '2.02';
+$VERSION = '2.13';
 
 # constant.pm is slow
 sub SUCCESS () { 1 }
@@ -17,13 +18,13 @@ my $Fattr = \%fields::attr;
 sub has_fields {
     my($base) = shift;
     my $fglob = ${"$base\::"}{FIELDS};
-    return $fglob && *$fglob{HASH};
+    return( ($fglob && 'GLOB' eq ref($fglob) && *$fglob{HASH}) ? 1 : 0 );
 }
 
 sub has_version {
     my($base) = shift;
     my $vglob = ${$base.'::'}{VERSION};
-    return $vglob && *$vglob{SCALAR};
+    return( ($vglob && *$vglob{SCALAR}) ? 1 : 0 );
 }
 
 sub has_attr {
@@ -37,20 +38,27 @@ sub get_attr {
     return $Fattr->{$_[0]};
 }
 
-sub get_fields {
-    # Shut up a possible typo warning.
-    () = \%{$_[0].'::FIELDS'};
+if ($] < 5.009) {
+    *get_fields = sub {
+        # Shut up a possible typo warning.
+        () = \%{$_[0].'::FIELDS'};
+        my $f = \%{$_[0].'::FIELDS'};
 
-    return \%{$_[0].'::FIELDS'};
-}
+        # should be centralized in fields? perhaps
+        # fields::mk_FIELDS_be_OK. Peh. As long as %{ $package . '::FIELDS' }
+        # is used here anyway, it doesn't matter.
+        bless $f, 'pseudohash' if (ref($f) ne 'pseudohash');
 
-sub show_fields {
-    my($base, $mask) = @_;
-    my $fields = \%{$base.'::FIELDS'};
-    return grep { ($Fattr->{$base}[$fields->{$_}] & $mask) == $mask} 
-                keys %$fields;
+        return $f;
+    }
+}
+else {
+    *get_fields = sub {
+        # Shut up a possible typo warning.
+        () = \%{$_[0].'::FIELDS'};
+        return \%{$_[0].'::FIELDS'};
+    }
 }
-
 
 sub import {
     my $class = shift;
@@ -61,55 +69,60 @@ sub import {
     my $fields_base;
 
     my $inheritor = caller(0);
+    my @isa_classes;
 
+    my @bases;
     foreach my $base (@_) {
-        next if $inheritor->isa($base);
+        if ( $inheritor eq $base ) {
+            warn "Class '$inheritor' tried to inherit from itself\n";
+        }
+
+        next if grep $_->isa($base), ($inheritor, @bases);
 
         if (has_version($base)) {
-	    ${$base.'::VERSION'} = '-1, set by base.pm' 
-	      unless defined ${$base.'::VERSION'};
+            ${$base.'::VERSION'} = '-1, set by base.pm' 
+              unless defined ${$base.'::VERSION'};
         }
         else {
-            local $SIG{__DIE__} = 'IGNORE';
-            eval "require $base";
-            # Only ignore "Can't locate" errors from our eval require.
-            # Other fatal errors (syntax etc) must be reported.
-            die if $@ && $@ !~ /^Can't locate .*? at \(eval /;
-            unless (%{"$base\::"}) {
-                require Carp;
-                Carp::croak(<<ERROR);
+            my $sigdie;
+            {
+                local $SIG{__DIE__};
+                eval "require $base";
+                # Only ignore "Can't locate" errors from our eval require.
+                # Other fatal errors (syntax etc) must be reported.
+                die if $@ && $@ !~ /^Can't locate .*? at \(eval /;
+                unless (%{"$base\::"}) {
+                    require Carp;
+                    local $" = " ";
+                    Carp::croak(<<ERROR);
 Base class package "$base" is empty.
-    (Perhaps you need to 'use' the module which defines that package first.)
+    (Perhaps you need to 'use' the module which defines that package first,
+    or make that module available in \@INC (\@INC contains: @INC).
 ERROR
-
+                }
+                $sigdie = $SIG{__DIE__} || undef;
             }
+            # Make sure a global $SIG{__DIE__} makes it out of the localization.
+            $SIG{__DIE__} = $sigdie if defined $sigdie;
             ${$base.'::VERSION'} = "-1, set by base.pm"
               unless defined ${$base.'::VERSION'};
         }
-        push @{"$inheritor\::ISA"}, $base;
-
-        # A simple test like (defined %{"$base\::FIELDS"}) will
-        # sometimes produce typo warnings because it would create
-        # the hash if it was not present before.
-        #
-        # We don't just check to see if the base in question has %FIELDS
-        # defined, we also check to see if it has -inheritable- fields.
-        # Its perfectly alright to inherit from multiple classes that have 
-        # %FIELDS as long as only one of them has fields to give.
+        push @bases, $base;
+
         if ( has_fields($base) || has_attr($base) ) {
-	    # Check to see if there are fields to be inherited.
-	    if ( show_fields($base, PUBLIC) or
-                 show_fields($base, PROTECTED) ) {
-		# No multiple fields inheritence *suck*
-		if ($fields_base) {
-		    require Carp;
-		    Carp::croak("Can't multiply inherit %FIELDS");
-		} else {
-		    $fields_base = $base;
-		}
-	    }
+            # No multiple fields inheritance *suck*
+            if ($fields_base) {
+                require Carp;
+                Carp::croak("Can't multiply inherit fields");
+            } else {
+                $fields_base = $base;
+            }
         }
     }
+    # Save this until the end so it's all or nothing if the above loop croaks.
+    push @{"$inheritor\::ISA"}, @isa_classes;
+
+    push @{"$inheritor\::ISA"}, @bases;
 
     if( defined $fields_base ) {
         inherit_fields($inheritor, $fields_base);
@@ -130,10 +143,11 @@ sub inherit_fields {
     $dattr->[0] = @$battr;
 
     if( keys %$dfields ) {
-        warn "$derived is inheriting from $base but already has its own ".
-             "fields!\n".
-             "This will cause problems with pseudo-hashes.\n".
-             "Be sure you use base BEFORE declaring fields\n";
+        warn <<"END";
+$derived is inheriting from $base but already has its own fields!
+This will cause problems.  Be sure you use base BEFORE declaring fields.
+END
+
     }
 
     # Iterate through the base's fields adding all the non-private
@@ -142,23 +156,24 @@ sub inherit_fields {
     # This is all too complicated to do efficiently with add_fields().
     while (my($k,$v) = each %$bfields) {
         my $fno;
-	if ($fno = $dfields->{$k} and $fno != $v) {
-	    require Carp;
-	    Carp::croak ("Inherited %FIELDS can't override existing %FIELDS");
-	}
+        if ($fno = $dfields->{$k} and $fno != $v) {
+            require Carp;
+            Carp::croak ("Inherited fields can't override existing fields");
+        }
 
         if( $battr->[$v] & PRIVATE ) {
-            $dattr->[$v] = undef;
+            $dattr->[$v] = PRIVATE | INHERITED;
         }
         else {
             $dattr->[$v] = INHERITED | $battr->[$v];
-
-            # Derived fields must be kept in the same position as the
-            # base in order to make "static" typing work with psuedo-hashes.
-            # Alas, this kills multiple field inheritance.
             $dfields->{$k} = $v;
         }
     }
+
+    foreach my $idx (1..$#{$battr}) {
+        next if defined $dattr->[$idx];
+        $dattr->[$idx] = $battr->[$idx] & INHERITED;
+    }
 }
 
 
@@ -168,7 +183,7 @@ __END__
 
 =head1 NAME
 
-base - Establish IS-A relationship with base class at compile time
+base - Establish an ISA relationship with base classes at compile time
 
 =head1 SYNOPSIS
 
@@ -177,39 +192,65 @@ base - Establish IS-A relationship with base class at compile time
 
 =head1 DESCRIPTION
 
-Roughly similar in effect to
+Allows you to both load one or more modules, while setting up inheritance from
+those modules at the same time.  Roughly similar in effect to
 
+    package Baz;
     BEGIN {
         require Foo;
         require Bar;
         push @ISA, qw(Foo Bar);
     }
 
-Will also initialize the fields if one of the base classes has it.
-Multiple Inheritence of fields is B<NOT> supported, if two or more
-base classes each have inheritable fields the 'base' pragma will
-croak.  See L<fields>, L<public> and L<protected> for a description of
-this feature.
+C<base> employs some heuristics to determine if a module has already been
+loaded, if it has it doesn't try again. If C<base> tries to C<require> the
+module it will not die if it cannot find the module's file, but will die on any
+other error. After all this, should your base class be empty, containing no
+symbols, it will die. This is useful for inheriting from classes in the same
+file as yourself, like so:
+
+        package Foo;
+        sub exclaim { "I can have such a thing?!" }
+        
+        package Bar;
+        use base "Foo";
+
+If $VERSION is not detected even after loading it, <base> will define $VERSION
+in the base package, setting it to the string C<-1, set by base.pm>.
+
+C<base> will also initialize the fields if one of the base classes has it.
+Multiple inheritance of fields is B<NOT> supported, if two or more base classes
+each have inheritable fields the 'base' pragma will croak. See L<fields>,
+L<public> and L<protected> for a description of this feature.
+
+The base class' C<import> method is B<not> called.
 
-When strict 'vars' is in scope, I<base> also lets you assign to @ISA
-without having to declare @ISA with the 'vars' pragma first.
 
-If any of the base classes are not loaded yet, I<base> silently
-C<require>s them (but it won't call the C<import> method).  Whether to
-C<require> a base class package is determined by the absence of a global
-$VERSION in the base package.  If $VERSION is not detected even after
-loading it, I<base> will define $VERSION in the base package, setting it to
-the string C<-1, set by base.pm>.
+=head1 DIAGNOSTICS
 
+=over 4
+
+=item Base class package "%s" is empty.
+
+base.pm was unable to require the base package, because it was not
+found in your path.
+
+=item Class 'Foo' tried to inherit from itself
+
+Attempting to inherit from yourself generates a warning.
+
+    use Foo;
+    use base 'Foo';
+
+=back
 
 =head1 HISTORY
 
 This module was introduced with Perl 5.004_04.
 
-
 =head1 CAVEATS
 
-Due to the limitations of the pseudo-hash implementation, you must use
+Due to the limitations of the implementation, you must use
 base I<before> you declare any of your own fields.