[#19] Implemented 'virtual' keyword

- Baby steps. 'override' keyword is not yet necessary.
- Final not yet removed

lib/member_builder.js

@@ -164,10 +164,13 @@ function validateMethod( keywords, prev_data, value, name )
             );
         }
 
-        // final methods cannot be overridden
-        if ( prev_keywords[ 'final' ] )
+        // Can only override virtual methods. Abstract methods are considered to
+        // be virtual.
+        if ( !( prev_keywords[ 'virtual' ] || prev_keywords[ 'abstract' ] ) )
         {
-            throw TypeError( "Cannot override final method '" + name + "'" );
+            throw TypeError(
+                "Cannot override non-virtual method '" + name + "'"
+            );
         }
 
         // do not allow overriding concrete methods with abstract
@@ -391,10 +394,16 @@ function scanMembers( members, name, base )
     {
         if ( member = members[ visibility[ i ] ][ name ] )
         {
-            return {
-                member:     member,
-                visibility: ( ( fallback ) ? 0 : i ),
-            };
+            // We need to filter out base properties (such as
+            // Object.prototype.toString()), but we still need to traverse the
+            // prototype chain. As such, we cannot use hasOwnProperty().
+            if ( member !== Object.prototype[ name ] )
+            {
+                return {
+                    member:     member,
+                    visibility: ( ( fallback ) ? 0 : i ),
+                };
+            }
         }
     }
 

lib/prop_parser.js

@@ -34,6 +34,7 @@ var _keywords = {
     'final':     true,
     'abstract':  true,
     'const':     true,
+    'virtual':   true,
 };
 
 

test/test-class-abstract.js

@@ -106,6 +106,28 @@ var common = require( './common' ),
 } )();
 
 
+/**
+ * Abstract methods should remain virtual until they are overridden. That is, if
+ * a subtype doesn't provide a concrete implementation, it should still be
+ * considered virtual.
+ */
+( function testAbstractMethodsCanBeOverriddenBySubSubTypes()
+{
+    var AbstractFoo = AbstractClass( 'Foo',
+        {
+            'abstract foo': [],
+        } ),
+
+        SubAbstractFoo = AbstractClass.extend( AbstractFoo, {} ),
+
+        ConcreteFoo = Class.extend( SubAbstractFoo,
+        {
+            'foo': function() {},
+        } )
+    ;
+} )();
+
+
 /**
  * Just as Class contains an extend method, so should AbstractClass.
  */

test/test-class-implement.js

@@ -175,7 +175,8 @@ var Type = Interface.extend( {
             foo2: function() {},
         }),
 
-        concrete_inst = new ConcreteFoo();
+        concrete_inst = ConcreteFoo()
+    ;
 
     assert.ok(
         ( concrete_inst.isInstanceOf( Type )

test/test-class-parent.js

@@ -34,13 +34,13 @@ var common = require( './common' ),
 
     Foo = Class.extend(
     {
-        myMethod: function()
+        'virtual myMethod': function()
         {
             hitMethod = true;
             return this;
         },
 
-        myMethod2: function( arg )
+        'virtual myMethod2': function( arg )
         {
             hitMethod2 = true;
             method2Arg = arg;

test/test-class-visibility.js

@@ -47,7 +47,7 @@ var common    = require( './common' ),
         'private privf':   privf,
 
 
-        'public getProp': function( name )
+        'virtual public getProp': function( name )
         {
             // return property, allowing us to break encapsulation for
             // protected/private properties (for testing purposes)
@@ -79,7 +79,7 @@ var common    = require( './common' ),
         },
 
 
-        'public getSelfOverride': function()
+        'virtual public getSelfOverride': function()
         {
             // override me
         },
@@ -516,7 +516,7 @@ var common    = require( './common' ),
         Class(
         {
             'protected foo': 'bar',
-            'protected baz': function() {},
+            'virtual protected baz': function() {},
         } ).extend( {
             'public foo': 'bar',
             'public baz': function() {},
@@ -529,7 +529,7 @@ var common    = require( './common' ),
         Class(
         {
             'protected foo': 'bar',
-            'protected baz': function() {},
+            'virtual protected baz': function() {},
         } ).extend( {
             'protected foo': 'bar',
             'protected baz': function() {},
@@ -621,7 +621,7 @@ var common    = require( './common' ),
 {
     var val = 'foobar',
         result = Class( {
-            'protected foo': function()
+            'virtual protected foo': function()
             {
                 return val;
             },
@@ -672,7 +672,7 @@ var common    = require( './common' ),
     // get the result of invoking overridden foo()
     var result = Class(
         {
-            'protected foo': function()
+            'virtual protected foo': function()
             {
                 return false;
             },
@@ -739,7 +739,7 @@ var common    = require( './common' ),
     var val    = 'foobar',
         result = Class(
         {
-            'protected foo': function() {},
+            'virtual protected foo': function() {},
         } ).extend(
         {
             // provide concrete implementation

test/test-member_builder-method.js

@@ -65,6 +65,122 @@ mb_common.assertCommon();
 } )();
 
 
+/**
+ * Unlike Java, PHP, Python and similar languages, methods in ease.js are *not*
+ * virtual by default. In order to make them override-able, the 'virtual'
+ * keyword must be specified for that method in the supertype.
+ *
+ * Therefore, let's ensure that non-virtual methods cannot be overridden.
+ */
+( function testCannotOverrideNonVirtualMethod()
+{
+    mb_common.value = function() {};
+    mb_common.buildMemberQuick();
+
+    try
+    {
+        // attempt to override (should throw exception; non-virtual)
+        mb_common.buildMemberQuick( {}, true );
+
+        // should not get to this point
+        assert.fail( "Should not be able to override non-virtual method" );
+    }
+    catch ( e )
+    {
+        // ensure we have the correct error
+        assert.ok(
+            e.message.search( 'virtual' ) !== -1,
+            "Error message for non-virtual override should mention virtual"
+        );
+
+        assert.ok(
+            e.message.search( mb_common.name ) !== -1,
+            "Method name should be provided in non-virtual error message"
+        );
+    }
+} )();
+
+
+/**
+ * Working off of what was said in the test directly above, we *should* be able
+ * to override virtual methods.
+ */
+( function testCanOverrideVirtualMethods()
+{
+    // build a virtual method
+    mb_common.value = function() {};
+    mb_common.buildMemberQuick( { 'virtual': true } );
+
+    // attempt to override it
+    assert.doesNotThrow( function()
+    {
+        mb_common.buildMemberQuick( {}, true );
+    }, Error, "Should be able to override virtual methods" );
+} )();
+
+
+/**
+ * Unlike languages like C++, ease.js does not automatically mark overridden
+ * methods as virtual. C# and some other languages offer a 'seal' keyword or
+ * similar in order to make overridden methods non-virtual. In that sense,
+ * ease.js will "seal" overrides by default.
+ */
+( function testOverriddenMethodsAreNotVirtualByDefault()
+{
+    // build a virtual method
+    mb_common.value = function() {};
+    mb_common.buildMemberQuick( { 'virtual': true } );
+
+    // override it (non-virtual)
+    mb_common.buildMemberQuick( {}, true );
+
+    // attempt to override again (should fail)
+    assert.throws( function()
+    {
+        mb_common.buildMemberQuick( {}, true );
+    }, TypeError, "Overrides are not declared as virtual by default" );
+} )();
+
+
+/**
+ * Given the test directly above, we can therefore assume that it should be
+ * permitted to declare overridden methods as virtual.
+ */
+( function testCanDeclareOverridesAsVirtual()
+{
+    // build a virtual method
+    mb_common.value = function() {};
+    mb_common.buildMemberQuick( { 'virtual': true } );
+
+    // override it (virtual)
+    mb_common.buildMemberQuick( { 'virtual': true }, true );
+
+    // attempt to override again
+    assert.doesNotThrow( function()
+    {
+        mb_common.buildMemberQuick( {}, true );
+    }, Error, "Can override an override if declared virtual" );
+} )();
+
+
+/**
+ * Abstract members exist to be overridden. As such, they should be considered
+ * virtual.
+ */
+( function testAbstractMethodsAreConsideredVirtual()
+{
+    // build abstract method
+    mb_common.value = function() {};
+    mb_common.buildMemberQuick( { 'abstract': true } );
+
+    // we should be able to override it
+    assert.doesNotThrow( function()
+    {
+        mb_common.buildMemberQuick( {}, true );
+    }, Error, "Can overrde abstract methods" );
+} )();
+
+
 /**
  * To ensure interfaces of subtypes remain compatible with that of their
  * supertypes, the parameter lists must match and build upon each other.
@@ -72,17 +188,17 @@ mb_common.assertCommon();
 ( function testMethodOverridesMustHaveEqualOrGreaterParameters()
 {
     mb_common.value = function( one, two ) {};
-    mb_common.buildMemberQuick();
+    mb_common.buildMemberQuick( { 'virtual': true } );
 
     assert.doesNotThrow( function()
     {
-        mb_common.buildMemberQuick( {}, true );
+        mb_common.buildMemberQuick( { 'virtual': true }, true );
     }, TypeError, "Method can have equal number of parameters" );
 
     assert.doesNotThrow( function()
     {
         mb_common.value = function( one, two, three ) {};
-        mb_common.buildMemberQuick( {}, true );
+        mb_common.buildMemberQuick( { 'virtual': true }, true );
     }, TypeError, "Method can have greater number of parameters" );
 
     assert.throws( function()
@@ -112,7 +228,7 @@ mb_common.assertCommon();
         orig_called = true;
     };
 
-    mb_common.buildMemberQuick();
+    mb_common.buildMemberQuick( { 'virtual': true } );
 
     // override method
     mb_common.value = function()
@@ -169,6 +285,10 @@ mb_common.assertCommon();
         super_called = true;
     };
 
+    // XXX: Bad idea. Set the keyword in another manner. This is likely to break
+    // in the future.
+    members['public'].foo.___$$keywords$$ = { 'virtual': true };
+
     // override
     builder.buildMethod( members, {}, 'foo', newfunc, {}, instCallback );
 
@@ -236,7 +356,7 @@ mb_common.assertCommon();
             return instance;
         },
 
-        members = { 'public': {}, 'protected': {}, 'private': {} }
+        members = builder.initMembers()
     ;
 
     // set instance values
@@ -249,7 +369,7 @@ mb_common.assertCommon();
         exports.meta,
         'func',
         func,
-        [ 'public' ],
+        { 'virtual': true },
         instCallback
     );
 
@@ -265,7 +385,7 @@ mb_common.assertCommon();
         exports.meta,
         'func',
         func2,
-        [ 'public' ],
+        {},
         instCallback
     );