From 2136ebedd50082f1cf1da14db82ac554ec783ad8 Mon Sep 17 00:00:00 2001
From: Mike Gerwitz <mike@mikegerwitz.com>
Date: Thu, 15 Dec 2011 22:58:23 -0500
Subject: [PATCH] Now properly handling extending from objects and properly
 throwing errors for scalars

---
 lib/ClassBuilder.js       | 34 +++++++++++++++++++++++++---------
 test/test-class-extend.js | 31 +++++++++++++++++++++++++++++++
 2 files changed, 56 insertions(+), 9 deletions(-)

diff --git a/lib/ClassBuilder.js b/lib/ClassBuilder.js
index 868c384..50fd123 100644
--- a/lib/ClassBuilder.js
+++ b/lib/ClassBuilder.js
@@ -294,7 +294,7 @@ exports.prototype.build = function extend( _, __ )
     var args      = Array.prototype.slice.call( arguments ),
         props     = args.pop() || {},
         base      = args.pop() || exports.ClassBase,
-        prototype = new base(),
+        prototype = this._getBase( base ),
         cname     = '',
 
         prop_init      = this._memberBuilder.initMembers(),
@@ -309,12 +309,6 @@ exports.prototype.build = function extend( _, __ )
             || { __length: 0 }
     ;
 
-    // must extend from constructor or class
-    if ( typeof base !== 'function' )
-    {
-        throw TypeError( "Must extend from class or constructor");
-    }
-
     // prevent extending final classes
     if ( base.___$$final$$ === true )
     {
@@ -424,6 +418,27 @@ exports.prototype.build = function extend( _, __ )
 };
 
 
+exports.prototype._getBase = function( base )
+{
+    var type = ( typeof base );
+
+    switch ( type )
+    {
+        // constructor (we could also check to ensure that the return value of
+        // the constructor is an object, but that is not our concern)
+        case 'function':
+            return new base();
+
+        // we can use objects as the prototype directly
+        case 'object':
+            return base;
+    }
+
+    // scalars
+    throw TypeError( 'Must extend from Class, constructor or object' );
+};
+
+
 exports.prototype.buildMembers = function buildMembers(
     props, class_id, base, prop_init, abstract_methods, members,
     static_members, staticInstLookup
@@ -758,11 +773,12 @@ exports.prototype._attachPropInit = function(
         // defaults to false
         inherit = !!inherit;
 
-        var iid = this.__iid;
+        var iid    = this.__iid,
+            parent = prototype.___$$parent$$;
 
         // first initialize the parent's properties, so that ours will overwrite
         // them
-        var parent_init = prototype.___$$parent$$.__initProps;
+        var parent_init = parent && parent.__initProps;
         if ( typeof parent_init === 'function' )
         {
             // call the parent prop_init, letting it know that it's been
diff --git a/test/test-class-extend.js b/test/test-class-extend.js
index 50e9890..8b9add3 100644
--- a/test/test-class-extend.js
+++ b/test/test-class-extend.js
@@ -432,3 +432,34 @@ for ( var i = 0; i < class_count; i++ )
     assert.fail( "Should not be permitted to override non-virtual method" );
 } )();
 
+
+/**
+ * If we attempt to extend an object (rather than a constructor), we should
+ * simply use that as the prototype directly rather than attempting to
+ * instantiate it.
+ */
+( function testExtendingObjectWillNotAttemptInstantiation()
+{
+    var obj = { foo: 'bar' };
+
+    assert.equal( obj.foo, Class.extend( obj, {} )().foo,
+        'Should be able to use object as prototype'
+    );
+} )();
+
+
+/**
+ * It only makes sense to extend from an object or function (constructor, more
+ * specifically)
+ *
+ * We could also test to ensure that the return value of the constructor is an
+ * object, but that is unnecessary for the time being.
+ */
+( function testWillThrowExceptionIfNonObjectOrCtorIsProvided()
+{
+    assert['throws']( function()
+    {
+        Class.extend( 'foo', {} );
+    }, TypeError, 'Should not be able to extend from non-object or non-ctor' );
+} )();
+