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easejs/test/test-member_builder-method.js

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JavaScript

/**
* Tests method builder
*
* Copyright (C) 2010 Mike Gerwitz
*
* This file is part of ease.js.
*
* ease.js is free software: you can redistribute it and/or modify it under the
* terms of the GNU Lesser General Public License as published by the Free
* Software Foundation, either version 3 of the License, or (at your option)
* any later version.
*
* This program is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* @author Mike Gerwitz
* @package test
*/
var common = require( './common' ),
assert = require( 'assert' ),
mb_common = require( __dirname + '/inc-member_builder-common' ),
builder = common.require( 'member_builder' ),
util = common.require( 'util' )
;
mb_common.funcVal = 'foobar';
mb_common.value = function() { return mb_common.funcVal; };
mb_common.buildMember = builder.buildMethod;
// do assertions common to all member builders
mb_common.assertCommon();
/**
* One may question the purpose of this assertion. Why should we not permit
* overriding properties with methods? It's useful to be able to store callbacks
* and such within properties.
*
* Yes, it is. However, that would be misinterpreting the purpose of the method
* builder. Here, we are working with prototypes, not class instances. If the
* user wishes to assign a function to the property (so long as it's permitted
* by the type definition) after the class is instantiated, he/she may go right
* ahead. However, if we modify the prototype to use a function, then the
* prototype will interpret the function as a method. As such, the method cannot
* be overridden with a property in the future. To avoid this confusing
* scenario, we'll prevent it from occurring entirely.
*/
( function testCannotOverridePropertyWithMethod()
{
mb_common.value = 'moofoo';
mb_common.funcVal = undefined;
// temporarily alter builder
mb_common.buildMember = builder.buildProp;
mb_common.buildMemberQuick();
// restore builder
mb_common.buildMember = builder.buildMethod;
assert.throws( function()
{
// attempt to override with function
mb_common.value = function() {};
mb_common.buildMemberQuick( {}, true );
}, TypeError, "Cannot override property with method" );
} )();
/**
* 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 );
}
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"
);
return;
}
assert.fail( "Should not be permitted to override non-virtual methods" );
} )();
/**
* 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" );
} )();
/**
* Static methods cannot realistically be declared as virtual; it doesn't make
* sense. Virtual implies that the method may be overridden, but static methods
* cannot be overridden. Only hidden.
*/
( function testCannotDeclareStaticMethodsAsVirtual()
{
mb_common.value = function() {};
try
{
// attempt to build a virtual static method (should throw exception)
mb_common.buildMemberQuick( { 'static': true, 'virtual': true } );
}
catch ( e )
{
assert.ok(
e.message.search( mb_common.name ) !== -1,
"Method name should be provided in virtual static error message"
);
return;
}
assert.fail( "Should not be permitted to declare a virtual static method" );
} )();
/**
* To ensure interfaces of subtypes remain compatible with that of their
* supertypes, the parameter lists must match and build upon each other.
*/
( function testMethodOverridesMustHaveEqualOrGreaterParameters()
{
mb_common.value = function( one, two ) {};
mb_common.buildMemberQuick( { 'virtual': true } );
assert.doesNotThrow( function()
{
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( { 'virtual': true }, true );
}, TypeError, "Method can have greater number of parameters" );
assert.throws( function()
{
mb_common.value = function( one ) {};
mb_common.buildMemberQuick( {}, true );
}, TypeError, "Method cannot have lesser number of parameters" );
} )();
/**
* The __super property is defined for method overrides and permits invoking the
* overridden method (method of the supertype).
*
* In this test, we are not looking to assert that __super matches the super
* method. Rather, we want to ensure it /invokes/ it. This is because the super
* method may be wrapped to provide additional functionality. We don't know, we
* don't care. We just want to make sure it's functioning properly.
*/
( function testOverridenMethodShouldContainReferenceToSuperMethod()
{
var orig_called = false;
// "super" method
mb_common.value = function()
{
orig_called = true;
};
mb_common.buildMemberQuick( { 'virtual': true } );
// override method
mb_common.value = function()
{
assert.notEqual(
this.__super,
undefined,
"__super is defined for overridden method"
);
this.__super();
assert.equal(
orig_called,
true,
"Invoking __super calls super method"
);
};
mb_common.buildMemberQuick( {}, true );
// invoke the method
mb_common.members[ 'public' ][ mb_common.name ]();
} )();
/**
* If the method is called when bound to a different context (e.g. for
* protected/private members), __super may not be properly bound.
*
* This test is in response to a bug found after implementing visibility
* support. The __super() method was previously defined on 'this', which may or
* may not be the context that is actually used. Likely, it's not.
*/
( function testSuperMethodWorksProperlyWhenContextDiffers()
{
var members = builder.initMembers(),
super_called = false,
retobj = {},
instCallback = function()
{
return retobj;
},
// the overriding method
newfunc = function()
{
this.__super();
}
;
// super method to be overridden
members[ 'public' ].foo = function()
{
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 );
// call the overriding method
members[ 'public' ].foo();
// ensure that the super method was called
assert.equal( super_called, true,
"__super() method is called even when context differs"
);
// finally, ensure that __super is no longer set on the returned object
// after the call to ensure that the caller cannot break encapsulation by
// stealing a method reference (sneaky, sneaky)
assert.equal( retobj.__super, undefined,
"__super() method is unset after being called"
);
} )();
/**
* Once a concrete implementation has been defined for a method, a subtype
* cannot make it abstract.
*/
( function testCannotOverrideConcreteMethodWithAbstractMethod()
{
// concrete method
mb_common.value = function() {};
mb_common.buildMemberQuick();
assert.throws( function()
{
mb_common.buildMemberQuick( { 'abstract': true }, true );
}, TypeError, "Cannot override concrete method with abstract method" );
} )();
/**
* One of the powerful features of the method builder is the ability to pass in
* an instance to be bound to 'this' when invoking a method. This has some
* important consequences, such as the ability to implement protected/private
* members.
*/
( function testMethodInvocationBindsThisToPassedInstance()
{
var instance = function() {},
val = 'fooboo',
val2 = 'fooboo2',
iid = 1,
func = function()
{
return this.foo;
},
func2 = function()
{
return this.foo2;
},
called = false,
instCallback = function()
{
called = true;
return instance;
},
members = builder.initMembers()
;
// set instance values
instance.foo = val;
instance.foo2 = val2;
// concrete method
mb_common.buildMember(
members,
exports.meta,
'func',
func,
{ 'virtual': true },
instCallback
);
assert.equal(
members[ 'public' ].func(),
val,
"Calling method will bind 'this' to passed instance"
);
// override method
mb_common.buildMember(
members,
exports.meta,
'func',
func2,
{},
instCallback
);
assert.equal(
members[ 'public' ].func(),
val2,
"Calling method override will bind 'this' to passed instance"
);
} )();
/**
* It does not make sense to be able to declare abstract private methods, since
* they cannot be inherited and overridden by subtypes.
*/
( function testCannotDeclareAbstractPrivateMethods()
{
mb_common.value = function() {};
assert.throws( function()
{
mb_common.buildMemberQuick( { 'private': true, 'abstract': true } );
}, TypeError, "Cannot declare private abstract method" );
} )();
/**
* While getters are technically methods, it doesn't make sense to override
* getters/setters with methods because they are fundamentally different.
*/
( function testCannotOverrideGetters()
{
if ( util.definePropertyFallback() )
{
return;
}
mb_common.members[ 'public' ] = {};
Object.defineProperty( mb_common.members[ 'public' ], mb_common.name, {
get: function() {},
} );
try
{
mb_common.value = function() {};
mb_common.buildMemberQuick( {}, true );
}
catch ( e )
{
assert.ok( e.message.search( mb_common.name ) !== -1,
"Method override getter failure should contain method name"
);
// ensure we have the correct error
assert.ok( e.message.search( 'getter' ) !== -1,
"Proper error is thrown for getter override failure"
);
return;
}
assert.fail(
"Should not be permitted to override getters with methods"
);
} )();
/**
* While setters are technically methods, it doesn't make sense to override
* getters/setters with methods because they are fundamentally different.
*/
( function testCannotOverrideSetters()
{
if ( util.definePropertyFallback() )
{
return;
}
mb_common.members[ 'public' ] = {};
Object.defineProperty( mb_common.members[ 'public' ], mb_common.name, {
set: function() {},
} );
try
{
mb_common.value = function() {};
mb_common.buildMemberQuick( {}, true );
}
catch ( e )
{
assert.ok( e.message.search( mb_common.name ) !== -1,
"Method override setter failure should contain method name"
);
// ensure we have the correct error
assert.ok( e.message.search( 'setter' ) !== -1,
"Proper error is thrown for setter override failure"
);
return;
}
assert.fail(
"Should not be permitted to override setters with methods"
);
} )();