Named trait staging object

The syntax Trait( "Name" ) now works as Class( "Name" ), permitting
implementing interfaces and extending from the staged object.

lib/Trait.js

@@ -36,17 +36,22 @@ function Trait()
 {
     switch ( arguments.length )
     {
+        case 0:
+            throw Error( "Missing trait name or definition" );
+
         case 1:
-            return Trait.extend.apply( this, arguments );
+            return ( typeof arguments[ 0 ] === 'string' )
-            break;
+                ? _createStaging.apply( this, arguments )
+                : Trait.extend.apply( this, arguments );
 
         case 2:
             return createNamedTrait.apply( this, arguments );
-            break;
-
-        default:
-            throw Error( "Missing trait name or definition" );
     }
+
+    throw Error(
+        "Expecting at most two arguments for definition of named " +
+            "Trait " + name + "'; " + arguments.length + " given"
+    );
 };
 
 
@@ -60,14 +65,6 @@ function Trait()
  */
 function createNamedTrait( name, dfn )
 {
-    if ( arguments.length > 2 )
-    {
-        throw Error(
-            "Expecting at most two arguments for definition of named " +
-                "Trait " + name + "'; " + arguments.length + " given"
-        );
-    }
-
     if ( typeof name !== 'string' )
     {
         throw Error(
@@ -76,11 +73,26 @@ function createNamedTrait( name, dfn )
     }
 
     dfn.__name = name;
-
     return Trait.extend( dfn );
 }
 
 
+function _createStaging( name )
+{
+    return {
+        extend: function( dfn )
+        {
+            return createNamedTrait( name, dfn );
+        },
+
+        implement: function()
+        {
+            return createImplement( arguments, name );
+        },
+    };
+}
+
+
 Trait.extend = function( dfn )
 {
     // we may have been passed some additional metadata
@@ -244,19 +256,37 @@ function _parseGetSet( name, value, keywords, h )
  */
 Trait.implement = function()
 {
-    var ifaces = arguments;
+    return createImplement( arguments );
+};
 
-    return {
+
-        extend: function()
+/**
+ * Create a staging object from which a trait implementing a set of
+ * interfaces may be defined
+ *
+ * @param  {...Function}  interfaces  interfaces to implement
+ * @param  {string=}      name        optional trait name
+ *
+ * @return  {Object}  staged trait object
+ */
+function createImplement( ifaces, name )
 {
+    return {
+        extend: function( dfn )
+        {
+            if ( name )
+            {
+                dfn.__name = name;
+            }
+
             // pass our interface metadata as the invocation context
-            return Trait.extend.apply(
+            return Trait.extend.call(
                 { __$$meta: { ifaces: ifaces } },
-                arguments
+                dfn
             );
         },
     };
-};
+}
 
 
 /**

test/Trait/NamedTest.js

@@ -1,7 +1,7 @@
 /**
  * Tests named trait definitions
  *
- *  Copyright (C) 2014 Free Software Foundation, Inc.
+ *  Copyright (C) 2014 Mike Gerwitz
  *
  *  This file is part of GNU ease.js.
  *
@@ -25,6 +25,7 @@ require( 'common' ).testCase(
     {
         this.Sut       = this.require( 'Trait' );
         this.Class     = this.require( 'class' );
+        this.Interface = this.require( 'interface' );
     },
 
 
@@ -84,4 +85,86 @@ require( 'common' ).testCase(
             Sut( {}, {} );
         } );
     },
+
+
+    /**
+     * Just as is the case with classes, providing only a name for the trait
+     * should create a staging object with which subsequent calls may be
+     * chained, just as if those calls were made on Trait directly. The
+     * difference is that the name shall propagate.
+     */
+    'Providing only trait name creates staging object': function()
+    {
+        var Sut = this.Sut;
+        this.assertDoesNotThrow( function()
+        {
+            // this does not create a trait, but it should be acceptable
+            // just as Class( "Foo" ) is
+            Sut( "Foo" );
+        } );
+    },
+
+
+    /**
+     * The named trait staging object should permit direct extension using
+     * an extend method, which should do the same thing as Trait.extend.
+     */
+    'Can extend named trait staging object': function()
+    {
+        var Sut      = this.Sut,
+            expected = {},
+            name     = "Foo",
+            T        = null;
+
+        this.assertDoesNotThrow( function()
+        {
+            // this does not create a trait, but it should be acceptable
+            // just as Class( "Foo" ) is
+            T = Sut( name )
+                .extend( { foo: function() { return expected; } } );
+        } );
+
+        // ensure that extending worked as expected
+        this.assertStrictEqual(
+            this.Class( {} ).use( T )().foo(),
+            expected
+        );
+
+        // ensure that trait was properly named
+        this.assertOk( T.toString().match( name ) );
+    },
+
+
+    /**
+     * The implement method on the named staging object should work just as
+     * Trait.implement.
+     */
+    'Can implement interface using named trait staging object':
+    function()
+    {
+
+        var Sut      = this.Sut,
+            expected = {},
+            name     = "Foo",
+            I        = this.Interface( {} ),
+            I2       = this.Interface( {} ),
+            T        = null;
+
+        this.assertDoesNotThrow( function()
+        {
+            // this does not create a trait, but it should be acceptable
+            // just as Class( "Foo" ) is
+            T = Sut( "Foo" )
+                .implement( I, I2 )
+                .extend( {} );
+        } );
+
+        // ensure that implement worked as intended
+        var inst = this.Class( {} ).use( T )();
+        this.assertOk( this.Class.isA( I, inst ) );
+        this.assertOk( this.Class.isA( I2, inst ) );
+
+        // ensure that trait was properly named
+        this.assertOk( T.toString().match( name ) );
+    },
 } );